Recently graduated Otolaryngology - Head and Neck Surgeons (OTO-HNS) are facing an employment crisis. To date, there has been no systematic evaluation of the factors contributing to this situation, graduating OTO-HNS trainee employment rates, nor the employment concerns of these graduating residents. This investigation sought to empirically evaluate prospective OTO-HNS graduate employment, identify factors contributing to this situation, and provide suggestions going forward.A cross-sectional survey of the 2014 graduating cohort of OTO-HNS residents was conducted 6-months prior to graduation, and immediately following residency graduation. Surveyed items focused on the demographics of the graduating cohort, their future training and employment plans, and their concerns relative to the OTO-HNS employment situation.All twenty-nine Canadian medical school graduated OTO-HNS residents completed the initial survey, with 93% responding at the completion of residency. Only 6 (22%) indicated confirmed employment following residency training. 78% indicated that they were pursuing fellowship training. 90% identified the pursuit of fellowship training as a moderately influenced by limited job opportunities. The ability to find and secure full-time employment, losing technical skills if underemployed/unemployed, and being required to consider working in a less-desired city/province were most concerning. 34% of the residents felt that they were appropriately counseled during their residency training about employment. 90% felt that greater efforts should be made to proactively match residency-training positions to forecasted job opportunities.Canadian OTO-HN Surgeons lack confirmed employment, are choosing to pursue fellowship training to defer employment, and are facing startling levels of under- and unemployment. A multitude of factors have contributed to this situation and immediate action is required to rectify this slowly evolving catastrophe. Otolaryngology – Head and Neck Surgery (OTO-HNS) is a broad medical and surgical discipline that cares for numerous prevalent head and neck conditions in patients of all ages. Both community and academic Otolaryngology – Head and Neck Surgeons provide a vital role in supporting primary care practitioners in the care of their patients. Canada-wide there are approximately 715 OTO-HN Surgeons, reflecting 2.1 Surgeons per 100,000 people . Prith, 2005  [Otolaryngology – Head and Neck Surgeons graduating from residency prior to June 30, 2000”)  are eligThe multifactorial increase in the number of Canadian OTO-HN Surgeons has resulted in growing levels of under- and unemployment, morphed practices, and “brain waste” . UnemploEthics approval was obtained from the University of Western Ontario Research Ethics Board.th, 2014) held in Halifax, Nova Scotia, Canada were invited to participate in this study. The goals of the investigation were announced to potential participants by one of the authors (MGB). Following the discussion of the goals of the investigation, a letter of information, consent form, and the investigative survey were distributed to all course attendees by a research assistant (GMS). Attendees were then voluntarily invited to participate in the completion of the research survey. Only the research assistant was present in the lecture theatre during survey distribution, completion, and collection and all course faculty were absent. All de-identified surveys were collected and retained by the research assistant, with data entry performed by the same assistant to ensure participant anonymity . Written feedback/comments that were provided by the survey participants were also confidentially collated and summarized by the research assistant (GMS). Given the small number of OTO-HNS residency programs and single province programs, participant geographic demographics were analyzed separately from survey responses to ensure complete participant anonymity and to maintain confidentiality. De-identified data summation and analysis were then performed by the investigative team (Microsoft Excel).All graduating OTO-HNS residents attending an annual OTO-HNS review course . The email was sent as a batched/grouped email with recipient blinding to all potential participants of the aforementioned “Annual OTO-HNS review course”. No individual participant was recruited directly. Participants were asked to voluntarily email the senior author (MGB) to report on their employment situation at the completion of residency. They were specifically asked to report: “Employed - Community OTOHNS: Yes/No; Employed - Academic OTOHNS: Yes/No; Fellowship - Yes/No; If pursuing a fellowship, employment contract post fellowship - Yes/No”. These data were collected, de-identified, and subsequently anonymously collated by the senior author (MGB). All participant emails were then deleted to ensure confidentiality.The investigative survey (Appendix A) was designed utilizing a group-consensus exercise. Items of investigative interest were discussed and summarized into survey questions which were then modified by the research team to ensure construct and content validity. Given the sensitive nature of the investigation and the requisite anonymity, no pilot testing was performed, nor were faculty at potential residency sites recruited to provide feedback relative to the survey.Descriptive statistics are presented as means with 95% confidence intervals as: mean .Twenty-nine postgraduate year five (PGY5) OTO-HNS residents completed the written survey in January 2014. This reflected 88% of the thirty-three 2014 graduating OTO-HNS trainees. The four non-participants were international medical graduates (IMG) who were asked to forgo study participation, thus, the present sample represents all (100%) of Canadian medical school graduates. Residents were on average 30 ± 2 years of age (Mean ± Standard Deviation), 76% (n = 22) were married, and 17% (n = 5) had children. The average estimated non-real-estate debt was assessed at approximately $100,000, with 34% (n = 10) carrying a debt-load greater than $100,000.Of the 29 respondents, 5 (17%) indicated confirmed employment following residency training with 3 of these residents noting that their prospective job was contingent on the completion of a fellowship. Only 2 graduating residents noted confirmed employment specific to a community Otolaryngology – Head and Neck Surgery position; 83% of graduating residents did not have a confirmed job.Of the 29 respondents, 18 were pursuing fellowship training (62%). A summary of fellowship training choices is presented in in Table Residents universally identified a high degree of concern about the job market facing them upon graduating as OTO-HNS trainees Figure . PotentiIn seeking additional information from respondents, 34% (n = 10) of the residents felt that they were appropriately counseled during their residency training about post-residency employment. However, 93% (n = 27) felt that their residency-training program should assist them in obtaining full-time employment; 90% (n = 26) of the graduating residents felt that greater efforts should be made to proactively match residency-training positions to forecasted job opportunities.The final component of the survey asked respondents to provide comments on items not addressed in the survey. These comments were focused on several key areas: matching of OTO-HNS residency spots to forecasted need and succession planning (6), employment transparency (2), lack of United States “board eligibility” (2), the need for additional clinical and post-graduate academic training to obtain positions (2), and the use of residents and recent graduates to maintain clinician lifestyles (2). Comments that focused on matching residency spots to forecasted need directly described the conflict of few job opportunities paired with long patient wait-times, the high demand for OTO-HNS service, and the perceived and advancing age of current practitioners. Those concerned about employment transparency identified perceived circumstances where advertised jobs had already been filled or promised to others. At the present time Canadian Otolaryngology – Head and Neck Surgeons are not eligible for board certification in the United States, and respondents identified this as a real and significant problem that impeded their ability to apply their training. For this reason, respondents perceived this problem to result in a backlog of “skill-decaying qualified trainees”. Concerns referencing enhanced training focused on the need to obtain advanced degrees and fellowships to obtain employment relative to other medical colleagues and non-physicians. Finally, two respondents were concerned with the maintenance of current resident numbers as a means of imposing on-call and clinic-only  positions on new graduates to improve the quality of life for fully employed OTO-HN Surgeons (in both the academic and community setting).The follow-up email survey in July 2014 demonstrated a 93% response rate (n = 27). Six participants indicated confirmed employment (22%) with 3 of these positions contingent on fellowship completion. Acknowledging non-respondents, these results show a single additional employed trainee from the initial January 2014 survey. Thus, 11% (n = 3) of the 2014 OTO-HNS cohort began practicing community OTO-HNS upon residency graduation. 11% (n = 3) of the participants reported that they were unemployed, reflecting a decrease from 6 respondents in the initial January survey. The number of participants pursuing fellowship training did however expand from 18 (62%) to 21 (78%).Canada is facing a specialist under- and unemployment crisis. As the number of Otolaryngology – Head and Neck Surgeons expands, graduating OTO-HN Surgeons are increasingly forced to wrestle with both professional and personal compromises as they formally enter their careers. Although the number of underemployed OTO-HN Surgeons is unknown, the data presented herein suggest that 22% n = 6) of the 2014 OTO-HNS graduating class have confirmed employment following residency or fellowship training, with only 11% (n = 3) entering the workforce immediately upon residency completion. Unlike the almost 40% of other graduating specialists [ of the 2The tightening Canadian job market appears to be forcing specialists to pursue even further training. Not surprisingly, 78% (n = 21) of those surveyed indicated that they were pursuing a sub-specialty fellowship. This number is striking as it is more than double that of the entire cohort of Royal College of Physicians and Surgeons of Canada Specialists who when recently surveyed suggest only 31% were pursuing advanced training . The ecoPredictably, the 2014 OTO-HNS graduating class identified securing full-time employment and losing technical skills as being of great concern. These findings align with concerns identified in both the National Physicians Survey and the Royal College employment survey ,6. FactoThe present data demonstrate a small number of employed graduating OTO-HNS residents and the substantial concerns these graduates face in entering the Canadian health care workforce. It is important to recognize that data from the initial and follow-up surveys are only reflective of employment conditions up to July 2014. Thus, employment rates identified herein may simply reflect the natural employment trend at that cross-sectional time-point and may not be indicative of true post-graduation employment. This is compounded by the absence of true under- and unemployment numbers amongst graduating OTO-HN Surgeons. Nevertheless, the trainees did identify substantial concerns over the employment landscape and its contributing factors. The existence of any involuntary under- or unemployment amongst Canadian OTO-HNS graduates is concerning and, therefor, as the number of OTO-HN Surgeons in Canada continues to expand and resource limitations remain the new normal, potential corrective strategies must be considered.Careful, well-reasoned, and systematic action must be taken to improve the current employment situation. As a starting point, consideration must be made to decreasing the current number of OTO-HNS resident trainees to more accurately reflect the job market – a strategy supported by 90% (n = 21) of those surveyed. The present rate of graduation is unsustainable even with a mythical retirement of all OTO-HN Surgeons over the age of 65. The positions vacated through the retirement of the 148 OTO-HN Surgeons over the age of 65 would be saturated within 5 years by the current pipeline of OTO-HNS residents (5-years x ~30 OTOHN Surgeons per year). A possible barrier to decreasing residency-training spots is the necessity of residents to provide quality and efficient patient care in high-volume academic centres. As such, efforts must be made to expand the utilization of allied healthcare workers including nurse practitioners and physician assistants to maintain adequate patient care while ensuring that OTO-HNS resident trainees remain highly skilled and employable. Unfortunately, this strategy has a 5-year lag time. In the immediate future, a new focus must be directed toward transitioned retirements, protection of current resources, and very possibly the sharing of current resources. Introducing new graduates into established OTO-HNS practices could allow these graduates to maintain their skills, benefit from the mentorship of an experienced colleague, and ensure succession planning for busy community OTO-HNS practices. Those transitioning into retirement could benefit from decreased on-call responsibilities and the potential to bridge retirement through the provision of non-operative OTO-HNS care. This strategy could be implemented at a national level through the Canadian Society of Otolaryngology – Head and Neck Surgery (CSO-HNS) or more locally through academic training centres and their alumni network. The significance of the current employment problems and the substantial role OTO-HN Surgeons play in improving the quality of life of Canadians must be highlighted at a national level. While other areas of surgical care may provide improved reimbursement opportunities, Canadians rely on Otolaryngology – Head and Neck Surgeons and, thus, hospital resources must remain stable for the continued care of communities. To this end, hospital based OTO-HNS resources  must be viewed collectively rather than individually. OTO-HNS groups should ensure balanced and appropriate operating room resource allocation amongst all members of the group and consideration must be made to the potential of hiring new graduates should an abundance of resources exist. Finally, ABOTO eligibility as a buffer to Canadian employment should be considered. This would certainly improve current and immediate rates of under- and unemployment, but is largely a Band-Aid™ solution as workforce planning should ensure that investments in the training of Canadian OTO-HNS Surgeons are met with Canadian opportunities for these Surgeons.In conclusion, the 2014 cohort of graduated Canadian Otolaryngology – Head and Neck Surgeons face real and substantial employment concerns and are choosing to pursue fellowship training to defer entering the job market. The potential for any involuntary under- and unemployment amongst those who have dedicated nearly a decade of their life to becoming OTO-HN Surgeons is unacceptable. A multitude of factors have contributed to this situation and immediate action is required to rectify this slowly evolving catastrophe.


Why are some scientific disciplines, such as sociology and psychology, more fragmented into conflicting schools of thought than other fields, such as physics and biology? Furthermore, why does high fragmentation tend to coincide with limited scientific progress? We analyzed a formal model where scientists seek to identify the correct answer to a research question. Each scientist is influenced by three forces: (i) signals received from the correct answer to the question; (ii) peer influence; and (iii) noise. We observed the emergence of different macroscopic patterns of collective exploration, and studied how the three forces affect the degree to which disciplines fall apart into divergent fragments, or so-called “schools of thought”. We conducted two simulation experiments where we tested (A) whether the three forces foster or hamper progress, and (B) whether disciplinary fragmentation causally affects scientific progress and vice versa. We found that fragmentation critically limits scientific progress. Strikingly, there is no effect in the opposite causal direction. What is more, our results shows that at the heart of the mechanisms driving scientific progress we find (i) social interactions, and (ii) peer disagreement. In fact, fragmentation is increased and progress limited if the simulated scientists are open to influence only by peers with very similar views, or when within-school diversity is lost. Finally, disciplines where the scientists received strong signals from the correct answer were less fragmented and experienced faster progress. We discuss model’s implications for the design of social institutions fostering interdisciplinarity and participation in science. Our starting points may be culturally determined, our paths may be affected by personal philosophies, but the fixed point is there nonetheless.” “[…] our entire universe from the mythical Big Bang via the emergence of hydrogen and helium, galaxies, fixed stars, planetary systems, viruses, bacteria, fleas, dogs to the Glorious Arrival of Western Man is an artifact constructed by generations of scientist-artisans from a partly yielding, partly resisting material of unknown properties.” The two quotes represent two opposing conceptions of science. The first quote by Steven Weinberg, Nobel Prize laureate in physics in 1979, represents a pure form of “scientific realism”, the conviction that science is able to accurately describe the world as it really is. Although the majority of natural scientists will agree with Weinberg’s statement, many scholars from the social sciences and humanities will disagree, as the second quote illustrates. This view implies that the process of developing scientific insights is largely influenced by social institutions, social norms, and conventions, making scientific knowledge the result of social construction –5.Interestingly, the fundamental difference in philosophical views between social and natural scientists seems to reflect how their fields are socially structured and how they progress. On the one hand, the natural sciences have typically experienced a sequence of unification processes that have produced a generally accepted canon of theories. In physics, for instance, Newton unified the celestial and terrestrial forces, and Maxwell unified electricity and magnetism in one single force called electromagnetism. Later on, Einstein unified the Newtonian theory of gravitation and his special relativity with the theory of general relativity. In more recent years on a subatomic level, the strong force, and the weak force have been unified with the electromagnetic force in one single model. This model is called the Standard Model and was discovered, among others, by Steven Weinberg. In addition, the natural sciences are often characterized by a high rate of scientific progress in terms of explanatory power and descriptive accuracy of their theories.The social sciences and humanities, on the other hand, are characterized by a high degree of fragmentation and slower scientific progress –8. In moHere, we study the question why disciplinary fragmentation and limited scientific progress appear to coincide often. Here, we present a general theory about the behavior of members of a scientific discipline, and use this theory to develop testable hypotheses about which of the causal processes shown in N = 100 scientists (agents) seeks to solve. This research problem is described by two real-valued variables, which create a two-dimensional epistemic space of possible answers, which scientists explore. We chose to model only two dimensions because it is computationally efficient, and easy to visualize [ground truth”.The theory is built around a research problem that a population of isualize . Howevert, each scientist i holds a certain view, i.e. his or her current answer to the research problem. This view is defined by the two coordinates that describe his or her position xi in the two-dimensional epistemic space. In addition, each scientist is moving through the epistemic space, exploring possible answers to the research question. We call the vector approach of the scientist. In sum, each scientist is described by three variables: (1) his or her current position, (2) the direction of exploration, and (3) the speed at which they move in the space of possible answers. That is, some scientists explore the space in rather small steps, because they feel that the true value is close to their current view. Others may explore at a much higher pace.At any moment in time t0, we implemented that all agents adopt a random position within a square of size 1 with the ground truth located in the center of the square. This square, however, does not limit the space of possible answers to the research problem, as agents can adjust their views in any direction, exploring answers that are outside of the range of initial views. Likewise, we assumed that agents initially adopt a random approach At the outset of the dynamics at time t, the computer program executes a random sequential update of the positions of all agents. To be more precise, the updated position is a function of the previous position and the approach. However, before the new position is determined, the computer program updates the approach of agent i based on Equation . In this case, each individual agent is exploring the epistemic space independently from the others. This movement, however, slows down and eventually stops when an agent reaches a point in the epistemic space where the strength of attraction towards the ground truth perfectly equals the absolute speed of exploration. In this situation, the force towards the truth points into the opposite direction of the agent’s approach. This balance between one’s own approach, and the information received from measurements completely determines the final position of the agent. On the collective level, the system reaches a state of equilibrium when all agents have stopped exploring the epistemic space. No consensus can be built under these conditions, and overall progress is limited.The collective dynamics that the model generates are graphically summarized in α > 0) can improve the situation. In the presence of social influence, agents adopt approaches and views that are similar to others, which leads to the formation of clusters. Within each cluster, agents have similar views but their approaches will initially point into different and sometimes even opposite directions. As a result of social influence, these differences in agents’ approaches are averaged out until all cluster members have adopted exactly the same approach. Averaging by social influence implies that the absolute exploration speed of the agents in the cluster is decreased. As a striking consequence, the point where the force of their approach is equal to the attraction by the ground truth is closer to the truth. For this reason, social influence facilitates progress. Nevertheless, after an initial loss in absolute speed, agents manage to perfectly align their approaches within a cluster. From that moment on, their speed will remain constant. In fact, the system is very likely to reach a state of equilibrium where the population consists of multiple homogeneous but mutually distant clusters with views that can be very far away from the ground truth.However, social influence  and progress (Arrow 3b). To this end, we manipulated the model parameters that determine the strength of the three forces guiding scientists behavior in our model and measured how this affected model predictions. In other words, we studied whether the attraction to the truth, social influence, and noise affect progress and fragmentation.Experiment 2 studied to which degree progress affects fragmentation (Arrow 1) and vice versa (Arrow 2). To this end, we experimentally manipulated the degree to which the simulated populations of researchers are fragmented and how distant their views are from the truth already at the beginning of the simulated research process. Our question was, whether the initial degrees of fragmentation and progress affected subsequent degrees of progress and fragmentation.In all simulation experiments we studied two outcome measures to quantify the structural patterns of disciplinary fragmentation and progress that the model generates. To measure the discipline’s progress at a given point in time, we calculated the average absolute Euclidean distance between agents’ current views and the ground truth. Obviously, higher values indicate a limited degree of scientific progress. As a measure of the degree of fragmentation, we focused on the number of clusters in the population. Further details about the implementation of the simulation experiments are available in Experiment 1 explored the effects of social influence, attraction by the ground truth, and noise on the degree of fragmentation and progress in the scientific discipline—Arrows 3a and 3b in R had profound effects on fragmentation and progress. It turned out that after 2,000 time steps agents almost always developed a global consensus whenever the interaction radius was equal or greater than 0.15 (Panel A). However, a more limited interaction radius fostered the formation of fragmented clusters. What is more, The bar graphs shown in R, we decided to always report two cases for the analyses of the remaining parameters: (i) a small influence radius of R = 0.03; and (ii) a large influence radius of R = 0.3.Having found the very strong effect of the interaction radius α of social influence. Panel A shows that the strength of social influence had an effect when the influence radius was small (R = 0.03). Under this condition, very weak social influence resulted in a higher degree of fragmentation. For instance, when α adopted a value of 0.01, the smallest value that we studied, we counted 30.2 clusters on average. When α was increased to 0.1, we counted only 15.9 clusters on average. However, when social influence was stronger than α = 0.25, a further increase in social influence strength hardly affected fragmentation. The populations with a large influence radius (R = 0.3) always reached a consensus within the 2.000 simulation events. However, when fragmentation was measured earlier in the simulation process  a similar effect obtains as for the simulations with the small influence radius.α can retard scientific progress was completely unexpected. This apparent anomaly can be explained as follows. A very strong social influence create very cohesive clusters very early in the simulation. We measured the average pairwise distance between agents in the biggest cluster, and it turned out to be significantly lower for very high values of α. The difference is small, but it counts for about one third of the size of the small interaction radius (R = 0.03). It is therefore enough to significantly reduce the process of merging of clusters at the beginning of the simulation. This leads to a lower average cluster size at the beginning of the simulated discipline, which in turn is the cause of the accumulated scientific retard measured after 2,000 iterations. On the other hand, such a gap is actually not permanent. If we let the simulations run for 20,000 iterations, we observe an approximately homogeneous degree of scientific progress for any value of α > 0.1  lines show regression estimates for those runs with the maximal  initial distance from the ground truth.R. In the case of a small radius (R = 0.03), there is a significant positive relationship between the number of initial clusters and the time necessary for reaching consensus. In the case of large radius (R = 0.3), we found a similar relationship, but much weaker. This difference results from the very strong tendency towards consensus that a large influence radius R implies. This tendency is so strong that the initial degree of fragmentation from the truth can only have a limited effect on the amount of time needed to reach a consensus on the true value.R = 0.03) and weak social influence (α = 0.01) never reached a state were at least 75 percent of the agents adopted views close to the ground truth, independently of the initial degree of fragmentation. Thus, even when there is a consensus already at the outset (1 cluster), progress was very limited when social influence was very weak.It turned out that the simulated disciplines with a small influence radius  require more time to collectively find the ground-truth. Moreover, if the interaction radius is small and agents are initially placed in a single cluster, it is extremely hard to reach a perfect consensus (100% consensus share). It takes even longer than if agents are initially split up into more clusters (2 to 5). This counter-intuitive finding is obtained because noise can lead some agents to leave their initial group. With a small influence radius, these isolated agents will remain isolated until they happen to join another cluster. This, however, can last very long or may never happen when there are very few clusters initially.In order to measure the degree of fragmentation, we counted the number of clusters at the point in time when 50 percent of the agents had adopted a view not further than 0.05 units away from the ground truth. We refrained from measuring fragmentation at some predefined number of iterations, because in some runs perfect consensus was reached very quickly, while in others lasted very long. We were, however, interested in the degree of fragmentation during the process of reaching the consensus. Furthermore, it turned out that 50 percent was a good threshold, as studying smaller shares implied that the initial degree of fragmentation basically explained the biggest part of the variance in later degrees of fragmentation. Larger values than 50 percent, on the other hand, imply that the theoretically possible number of clusters was reduced, which led to undesirably small variations in the outcome variable.Panel D in R, the strength of angular noise σ, and the strength of the attraction to the ground truth τ had significant effects on both fragmentation and progress. Experiment 2 showed, in addition, that fragmentation decreases progress, while progress has no effect on fragmentation. For the purpose of our study, it is crucial to check whether the effect of the three independent variables on progress is mediated by fragmentation. In other words, it is possible that the three independent variables studied in Experiment 1 are acting directly only on fragmentation, and by reducing it, they have an indirect effect on progress. We, therefore, implemented Baron and Kenny’s mediation test [R, σ, and τ. Further details about the mediation analysis are available in Experiment 1 showed that the social influence radius ion test  on the dR, σ, and τ) correlated significantly with progress. Second, we regressed fragmentation on the respective parameter. Once more, Experiment 1 has shown that the effect was present. Third, progress was regressed on fragmentation and the respective parameter. If the size of the statistical effect in Step 3 was smaller than in Step 1, we concluded that the parameter has both a direct and an indirect effect on progress. If the statistical effect even turned insignificant in the regression of Step 3, then we concluded that the effect of the parameter on progress is completely mediated by fragmentation.The mediation analysis consisted of three steps. First, we estimated a linear regression with progress as the dependent variable and one parameter as the independent variable. Experiment 1 already demonstrated that the three parameters . As R = 0.1. In turned out that in this subset of the simulations 69.5 percent of the effect of the influence radius R on progress was mediated by fragmentation. Thus, also the direct effect of the influence radius on progress remained significant. In sum, we found that the effect of parameter R on progress was partially mediated by fragmentation and that the direct effect remained significant.The influence radius ress see . The medσ had a strong effect on progress, as R = 0.03) as the effect of angular noise on progress was rather weak under R = 0.3. In addition, all runs quickly reached a consensus when the influence radius was large, leading to an extremely small variance in the degree of fragmentation when R = 0.3. For the simulations with the small influence radius, however, it turned out that 58.53 percent of total effect of angular noise on progress was mediated by fragmentation. The mediation was statistically significant according to the Preacher and Hayes test . What is more, σ turned insignificant in Step 3, showing that there is no support for a direct effect of parameter σ on progress.The angular noise τ of the attraction to the ground truth had a profound impact on progress, according to Experiment 1 . Similar effects were found for the simulations with the bigger influence radius (R = 0.3). Here 63.1 percent of the total effect on progress was mediated by fragmentation. . Nevertheless, we found a direct effect of the strength τ of the attraction to the ground truth.Also the strength riment 1 . The medR and the strength of attraction to ground truth τ were both responsible for a part of the relationship between progress and fragmentation. On the other hand, the effect of the parameter σ on progress was found completely mediated by fragmentation.In sum, the influence radius In this study, we asked why limited scientific progress and high degrees of disciplinary fragmentation tend to coincide. This correlation between fragmentation and progress could, in principle, result from three causal mechanisms see . First, Our approach was purely theoretical. Based on existing philosophical theories and formal models of social influence dynamics, we developed a computational model of scientific disciplines consisting of a population of scientists who seek to identify the correct answer to a research question. By means of two simulation experiments and with the help of statistical methods, we were able to establish whether and under which conditions these assumptions about individual behavior generated fragmentation and progress and study why the two outcomes correlated.the first answer to the question why progress and fragmentation correlate is that fragmentation causally affects progress. This conclusion is consistent with philosopher T. Kuhn’s view of pre-paradigmatic science, where progress is limited because much intellectual energy is wasted arguing over fundamentals with rival schools, instead of developing an original research tradition [We found that fragmentation hampered progress, but there was no effect in the opposite causal direction. In other words, limited progress is the consequence and not the cause of fragmentation. Thus, radition .we also found that the two outcomes were influenced by the same variables, which also explains why fragmentation and progress correlate. First, scientific progress and the degree of fragmentation turned out to depend on the strength of the attraction of the ground truth. Our model suggests that scientific disciplines in which views and approaches that are strongly influenced by the ground truth tend to experience less fragmentation and progress faster. The latter effect exists on top of the indirect effect via fragmentation.In addition, R and with angular noise σ, proved to have very strong effects.Furthermore, it turned out that increasing the social influence radius decreases the amount of fragmentation and facilitates progress. Thus, this variable also explains why progress and fragmentation are correlated according to our model. An important finding of our study is that social influence facilitates progress. This contradicts the criticism often heard that social processes would distract scientists in their scientific exploration. However, being open to peer influence is not enough. Progress remains limited when agents fail to consider the position of other scientists with distant views, or when deviations from the main approach are not allowed. These variables, which were operationalized with the influence radius our model identifies two core mechanisms fostering scientific progress: (i) social interactions, and (ii) peer disagreement. Similar conclusions have been reached also by contemporary philosophers of science, who argue that critical social interactions are the only way to acquire firm, and rationally based knowledge [In sum, nowledge .Our model is related to, but different from previous models of epistemic or fitness landscape exploration. In particular, our model assumes one single ground-truth in the epistemic space, instead of a rugged landscape . Even thFuture modeling work is needed to assess the sensitivity of our results to changes in model assumptions and to derive further hypotheses about the conditions of progress and fragmentation in scientific disciplines. For instance, our model is build around the assumptions that there is one and only one answer to the research problem that the agents study, that agents’ initial views are uniformly (randomly) distributed around this point of truth, and that scientists are attracted by the ground truth with a force that scales linearly with distance. Studying how changing any of these assumptions affects model predictions is certainly a worthwhile line of investigation. Furthermore, future research could manipulate the total number of agents, and experiment with alternative assumptions about agents’ behavior when they reached the border of a bounded epistemic space. Finally, a further important extension will be to relax the assumption that all agents are equally affected by the ground truth, peer influence, and noise.Obviously, a second crucial line of future research is to empirically test the predictions derived from our study. However, empirically studying which of the three causal mechanisms are responsible for the correlation between fragmentation and progress is very challenging, as the two outcomes and also the three independent variables are very difficult to quantify, and can hardly be manipulated experimentally. One promising approach to measure the degree of fragmentation in a discipline is to measure the degree of clustering in the network of citations in scientific publications . SubstanAn additional challenge for empirical research is to test whether the three independent variables of our study are flexible—e.g. they might change over time—and whether they are in fact causally affected by the outcome variables. For instance, it appears possible that scientists who work in a highly fragmented field limit the degree to which they are influenced by disagreeing others, or even seek to increase differences to clusters of scientists who disagree . In our Our model presented a coherent theory of why fragmentation come about in scientific disciplines, and what consequences it has on collective progress. However, alternative explanations can be found in the literature. Many of these, in particular those developed by social scientists, point to the problematic behavior of researchers in the social sciences. For instance, in his critique of the field, sociologist S. Cole  has arguAnother possible explanation might lie in the complexity of the subject of study. Positivist philosopher Auguste Comte (1798—1857) argued that knowledge develops faster the more general, the simpler, and the more independent is from other “departments”. Accordingly, he ranked the scientific disciplines established at his time in the following order: astronomy, physics, chemistry, biology, and sociology. Following Comte’s argument, it is possible to explain differences in levels of fragmentation across scientific disciplines as due to the different level of complexity of the subject of study. Comte’s hierarchy has been considered only as a theoretical entity for a long time, however, the recent abundance of bibliographic data has allowed researchers to actually put it under test. Landmark study by sociologist S. Cole could not find evidence in support of the existence of Comte’s hierarchy . HoweverOur findings point to possible measures to foster scientific progress. First of all, the finding that fragmentation is the cause and not the consequence of progress suggests that decreasing fragmentation will have positive effects on scientific progress. What is more, our results also show how fragmentation can be reduced. First and foremost, the simulated disciplines progressed much faster when agents were strongly attracted by the ground truth, showing that progress is increased when views and approaches are frequently confronted with empirical data. It has been often criticized that many researchers tend to neglect the outcomes of empirical studies . Our modvenues for critical and interactive discussion to take place. This would be the best way to support scientific progress. Online technologies are already altering the way scientists do research, and they provide a good chance for fragmented fields to get out of their deadlocked situation. But there is still a long way to go towards a more participative, problem-oriented, and interdisciplinary science.More concretely, our results could guide the design of social institutions that foster scientific progress. The most pervasive social institution in science is the peer-review system. Even though our model is highly abstract, it suggests that peer review could potentially foster progress, by exposing researchers to influence from others with different views and approaches. In reality, the complexity of the subject, the limited time and type of interaction, and the unbalanced incentives structure between authors and reviewers, are all factors that make peer review not well suited for long term discussions. In fact, as also suggested by philosopher of science Longino , we despS1 VideoThe video illustrates the model dynamics of four typical simulation scenarios.(MP4)Click here for additional data file.S1_TextDetailed description of computational experiments, mediation analysis, and boundary conditions.(PDF)Click here for additional data file.


Attention deficit and hyperactivity disorder (ADHD) and headache are two very common diseases in childhood and both of them have an important impact on quality of life and academic performance . In the Analysis of comorbility between ADHD and headache searching for the presence of ADHD trait in a population of headache patients.Observational study of case series based on collection of clinical-anamnestic data and on the administering of a standardized questionnaire  to evaluate the presence of ADHD traits in all the patients consecutively referred to the Juvenile Headache Centre of Padua (December 2014-May 2015). Inclusion criteria: age 5-18 years; diagnosis of primary headache, using the International Classification of Headache Disorders III, 2013 [Total sample of 180 cases  with mean age at interview of 11.8 years (8-18 years). Headache types: 120 migraine (M) (66.7%), 49 tension-type headache (TTH) (27.2%), 5 headaches with mixed pattern (M + TTH) (2.8%) and 6 other headaches (3.3%). M patients were divided into 107 MO (89.2%), 13 MA (10.8%); TTH were divided into 45 ETTH (91.8%) and 4 CTTH (8.2%). Family history for headache was present in 122/180 patients (71.8%), family history for M in 50/122 (41.0%). Prevalence of ADHD traits was 19.4% in SDQ questionnaires completed by parents and 21.3% in self-assessment SDQ questionnaires from children/adolescents. There was a low level of agreement between parents and children, reflecting heterogeneity symmetrical judgment between the two groups . There were no correlations with the diagnosis of headache or with other clinical features ; statistically significant relationships were found with the worsening of academic performance (p 0.001) and marginally with school absences (p 0.08).This study confirms most literature studies on the possible relationship between headache and ADHD, especially concerning the important impact on quality of life and academic performance –3. It coWritten informed consent to publish was obtained from the patient(s).


Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder with early onset. ADHD is associated with significant morbidity and mortality, partly due to delayed diagnosis. Identification of children at high risk for developing ADHD could lead to earlier diagnosis and potentially change the negative trajectory of the illness for the better. Since early psychosocial adversity is considered to be a likely etiological risk factor for ADHD, markers of this construct may be useful for early identification of children at high risk. Therefore, we sought to investigate whether Rutter’s indicators of adversity  assessed in infancy could serve as early predictors for the development of ADHD.st 1993 and December 31st 2011 and extracted dichotomous values for the six Rutter’s indicators of adversity at age 0–12 months (infancy) for each cohort member. The cohort members were followed from their second birthday and the association between the sum of Rutter’s indicators of adversity (RIA-score) in infancy and subsequent development of ADHD was estimated by means of Cox regression. Also, the number needed to screen (NNS) to detect one case of ADHD based on the RIA-scores in infancy was calculated. During follow-up (9.6 million person-years), 15,857 males and 5,663 females from the cohort developed ADHD. For both males and females, there was a marked dose-response relationship between RIA-scores assessed in infancy and the risk for developing ADHD. The hazard ratios for ADHD were 11.0 (95%CI: 8.2–14.7) and 11.4 (95%CI: 7.1–18.3) respectively, for males and females with RIA-scores of 5–6, compared to males and females with RIA-scores of 0. Among males with RIA-scores of 5–6, 37.6% (95%CI: 27.0–50.7) had been diagnosed with ADHD prior to the age of 20, corresponding to a NNS of 3.0 (95%CI: 2.2–4.0).Using data from the Danish nationwide population-based registers, we established a cohort consisting of all 994,407 children born in Denmark between January 1Rutter’s indicators of adversity assessed in infancy strongly predicted ADHD. This knowledge may be important for early identification of ADHD. Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder with early onset ,2. In a Early psychosocial adversity is considered to be a likely etiological risk factor for mental health problems, including ADHD ,9. This In order to test the predictive potential of RIA with regard to ADHD, we conducted a longitudinal study of a nationwide birth cohort using data on RIA and ADHD extracted from the Danish registers . To miniThis is a population-based historical prospective cohort study. Data was obtained by register linkage via the unique personal registration numbers, which are assigned to all Danes at the time of birth or when obtaining an address in Denmark .st 1993 and December 31st 2011, who were living in Denmark at their 2nd birthday, was established through the Danish Civil Registration System [st 2013.A cohort consisting of all children born in Denmark between January 1n System . Mothersst 1995 and December 31st 2013. Diagnostic data regarding ADHD was extracted from the Danish Psychiatric Central Research Register (DPCRR) [th International Classification of Diseases (ICD-8) [st 1994, when it was replaced by the 10th International Classification of Disease (ICD-10) [st 1995, we began follow-up of the subjects on January 1st 1995 at the earliest. To avoid bias due to the inclusion of cohort members with ADHD diagnosed prior to the initiation of follow-up, all individuals registered with a diagnosis of ADHD (defined by an ICD-10 diagnosis of F90.x or F98.8—or an ICD-8 diagnosis of 308.01) before their second birthday were excluded.The primary outcome of the study was the assignment of an ADHD-diagnosis following inpatient or outpatient contact at a psychiatric, neurological or pediatric department in Denmark, in the period between January 1 (DPCRR) . In thes (ICD-8)  was used(ICD-10) . IndividRIA were defined based on the nationwide Danish registers as described below. Due to the register-based nature of this study, we were unable to use the exact same definitions of RIA as derived by Rutter and colleagues –12 and tst and November 1st, respectively, in the cohort members’ year of birth. Similarly, the parents’ gross income was obtained for the subject’s year of birth.Low social class of the parents of the subjects was defined as both parents being classified as “low” on at least one of the following variables: education, occupation or income. We defined low education as only having completed compulsory schooling (or not having completed compulsory schooling). A score of low regarding occupation was defined as receiving disability pension . Finally, low income was defined as an income in the lowest fifth of the general population for each sex and calendar year. This variable was based on data from the Danish Education Registers  the Intest in the year following the subject’s year of birth, based on information from Statistics Denmark’s FAIN dataset [This variable was defined dichotomously according to whether both custodial parents were living at the same address as the subject or not on January 1 dataset .st in the year after the cohort member’s year of birth. Large family was defined dichotomously as a household with four or more children (including the cohort member) [Large family size was defined according to the number of children (<18 years of age) living in the household where the subject resided on January 1 member) . This va member) .st birthday.We defined paternal criminality dichotomously based on whether the father of the cohort member had ever received a custodial or suspended sentence for an offence under the principal Danish criminal acts , the special legislation regarding drugs and weapons, or sections of the traffic act dealing with impaired driving. The data for this variable was extracted from the Danish National Crime Register  using inThis variable was defined dichotomously based on whether the mother of the cohort member had ever been registered with a mental disorder (ICD-8 diagnoses: 290–315 and ICD-10 diagnoses: F00-F99) in the DPCRR. The variable was defined based on diagnoses registered from 1969 until the cohort members’ first birthday.This variable was defined dichotomously for each cohort member based on whether he or she had ever been placed outside home (in foster care or in an institution/orphanage) either with or without the parents’ consent. Data was extracted from the Register of Support for Children and Adolescents, which contains information on all placements made in Denmark since 1977 . The varThe data was analyzed by means of Cox regression using age as the underlying time-axis by means of the “stcox” command in Stata (version 13). Hazard ratios, Wald statistics, 95% confidence bands, and associated p-values were computed. All analyses were stratified by gender and adjusted for calendar year (1 year strata). The number needed to screen (NNS) was calculated as one divided by the difference between the risk of ADHD among cohort members with an increased RIA-score and those with a RIA-score equal to zero . The risFurthermore, to assess whether potential associations between elevated RIA-scores and ADHD were driven by large effects of single RIA, we conducted “leave-one-out” analyses in which each of the six RIA, in turn, were excluded from the RIA-score in the Cox regression analyses (carried out as described above) investigating the association between RIA-scores and ADHD . Finally, we assessed the pair-wise association between the RIA by means of Pearson correlation.In order to test the specificity of the association between RIA and ADHD, we included autism spectrum disorder (ASD) as “control” condition. ASD was chosen as control as the incidence pattern of this diagnostic category is that closest to ADHD among the major mental disorders . Based oThe use of data from the registers was approved by the Danish Data Protection Agency, the Danish National Board of Health and Statistics Denmark.st 1993 and December 31st 2011 to Danish born parents. Of these, 5,889 either died , emigrated / were lost to follow-up , or received an ADHD diagnosis (n = 200) before their second birthday. Thus, 994,407 children  were followed from their 2-year birthday yielding a total of 9,620,404 person-years of observation. The prevalence of the six RIA in infancy were as follows in this cohort: paternal criminality = 10.7%, severe marital discord = 9.9%, low social class = 9.1%, maternal mental disorder = 5.5%, large family size = 3.5%, placement in out-of-home care = 0.3%.We identified 1,000,296 children born between January 1During follow-up, 15,857 males and 5,663 females from the cohort were diagnosed with ADHD, corresponding to incidence rates of 3.2 (95%CI: 3.2–3.3) and 1.2 (95%CI: 1.2–1.2) per 1,000 person-years for males and females respectively. The results of the leave-one-out analyses are shown in The pair-wise association between RIA is shown in The results of the analysis of the association between RIA and ASD are reported in In this study of 994,407 children followed for more than 9.6 million person-years, we tested the association between Rutter’s indicators of adversity (RIA) score in infancy assessed via nationwide registers, and the risk for developing ADHD later in childhood/adolescence/early adulthood. The main finding was that the risk of ADHD increased in a dose-response like manner with increasing RIA load. This is consistent with findings from prior studies of smaller samples, where RIA were assessed later in childhood –16.As opposed to the five other RIA, large family size was not significantly associated with subsequent ADHD. In the early 1970’s, when the studies establishing RIA as risk factors for mental illness in children were conducted in the United Kingdom, having a large family was indicative of low socioeconomic status –12. This2 = 0.058) of the variance in paternal criminality is accounted for by low social class and vice versa.Despite the fact that our results show that there are substantial differences in the predictive ability of the various RIA, the maintained dose-response relationship across the leave-one-out analyses indicate that the RIA-ADHD association is not driven by a single indicator—and that it is reasonable to use the sum of the RIA as an overall measure of adversity. In further support of this practice, the relatively low values for the Pearson correlation coefficients stemming from the analysis of the pair-wise association of the RIA  indicateWhile early assessment of RIA in itself, as indicated by the low values for NNS, appear to be quite sensitive in identifying infants at risk for ADHD, particularly among males, the predictive ability is likely to be even higher for a composite “test-battery”. For instance, combining RIA assessment with biomarkers , evaluatSince the cohort studied here overlaps substantially with the one used in the recent study of mortality by Dalsgaard et al. , it seemFrom an etiological perspective, there is little doubt that RIA tap into both genetic and environmental causal mechanisms for ADHD, as well as interactions between the two . HoweverIn order to study the specificity of the RIA-ADHD association, we conducted analogue analyses of the association between RIA assessed in infancy and subsequent development of autism spectrum disorder (ASD). The results of these analysis showed, that while there were positive associations (hazard ratios above 1) between the RIA and ASD (apart from for large family size), the strength of these associations appears weaker than for those reported for RIA and ADHD compare . Also, tplacement in out-of-home care are quite similar to those used in other studies, the definition of severe marital discord differs more substantially. Since the registers do not contain information about the degree of conflicts among cohabiting individuals, we operationalized this particular variable dichotomously according to whether both custodial parents were living at the same address as the infant or not. Based on the present data, we are unable to determine whether this definition captures the same construct as that originally defined by Rutter and colleagues [The most important limitation of our study is the use of register-based approximations of RIA. While our definitions of low social class, large family size, paternal criminality, maternal mental disorder, and lleagues –12. Howelleagues –16, whicA related limitation of the study is the use of a register-based definition of ADHD. The diagnoses in the registers providing data for this study are clinical diagnoses, and are not necessarily assigned based on standardized research interviews as in most clinical studies. However, the validity of the clinical ADHD diagnoses in the registers is high ,45. The The register-based approach of this study also has important strengths. First of all, the sample size of 994,407 makes this the far largest study of the RIA-ADHD association ever conducted. Secondly, while most previous studies testing the association between RIA and ADHD –16 have In terms of generalizability, it is important to note that Denmark is among the most economically and socially equal welfare states in the world , and theAlthough it is still too early to make clinical recommendations based on associations of RIA and ADHD, this study is the first to show that assessment of RIA in infants may be useful in identifying individuals at high risk of developing ADHD later in childhood or adolescence. Ideally, this possibility should be subjected to prospective clinical investigation. Furthermore, although no causal inference can be made at this point, the strong dose-dependent association between RIA and ADHD, may imply that RIA represent etiological factors for ADHD. Since the etiology of ADHD remains unclear, this hypothesis seems worth pursuing in further studies.S1 Checklist(PDF)Click here for additional data file.S1 Table”N ASD” refers to the number of ASD cases in each stratum, while”N total” is the total number of individuals in each stratum. The rates are per 1,000 person-years. The hazard ratios (HR) are adjusted for calendar year (1 year strata). Information regarding low social class, severe marital discord and large family size was unavailable for 0.03%, 0.16%, and 0.16% of the ASD cases respectively. For the entire cohort, the corresponding proportions were 0.07%, 0.21% and 0.21%.(DOCX)Click here for additional data file.S2 TableThe number needed to screen was calculated as one divided by the difference between the risk of ADHD among cohort members with an increased RIA-score and those with a RIA-score equal to zero . The ris(DOCX)Click here for additional data file.S3 TableThe number needed to screen was calculated as one divided by the difference between the risk of ASD among cohort members with an increased RIA-score and those with a RIA-score equal to zero . The ris(DOCX)Click here for additional data file.S1 Text(DOCX)Click here for additional data file.


Objective. The majority of studies investigating neurocognitive processing in attention deficit/hyperactivity disorder (ADHD) have been conducted on male participants. Few studies evaluated females or examined sex differences. Among various cognitive anomalies in ADHD, deficit in forethought seems particularly important as children with ADHD often fail to adequately use previous information in order to prepare for responses. The main goal of this study was to assess sex-specific differences in behavioral and neural correlates of forethought in youth with ADHD. Methods. 21 typically developing (TD) youth and 23 youth with ADHD were asked to judge whether two pictures told a congruent or incongruent story. Reaction time, performance accuracy, and cerebral activations were recorded during functional magnetic resonance imaging (fMRI). Results. Significant sex-specific differences in cerebral activations appeared, despite equivalent performance. Relative to the boys TD participants, boys with ADHD had extensive bilateral frontal and parietal hypoactivations, while girls with ADHD demonstrated more scattered hypoactivations in the right cerebral regions. Conclusion. Present results revealed that youth with ADHD exhibit reduced cerebral activations during forethought. Nevertheless, the pattern of deficits differed between boys and girls, suggesting the use of a different neurocognitive strategy. This emphasizes the importance of including both genders in the investigations of ADHD. Attention deficit/hyperactive disorder (ADHD) is a neurodevelopmental disorder defined by persistent inattention and/or hyperactivity/impulsivity . The disThe expression of ADHD appears to be sexually dimorphic. Boys seem to exhibit more hyperactivity, inattention, impulsivity, and externalizing problems. Girls generally show more internalizing problems  and intellectual impairment , 5. LargSeveral executive dysfunctions have been found in children with ADHD, including difficulties with prioritizing, time management, and initiating and completing tasks as well as difficulty in shifting cognitive sets and poor working memory (WM) . WorkingOnly a few neuroimaging studies on ADHD have included females. The percentage of females across all studies has been estimated to be less than 20% . Valera Forethought is a prospective function of WM related to the ability to conjecture possible future related events  and [ADHD > TD],and interaction effects in the following simple contrasts: [TD boys > ADHD boys], [TD girls > ADHD girls], [ADHD boys > TD boys], and [ADHD girls > TD girls]. Statistical tests were performed for group comparisons at a threshold level of but weak .T-scores (> 60) on WCST also suggested lower mental flexibility (p = 0.017) but not between TD girls and girls with ADHD. Regarding Hit RT, higher scores for boys with ADHD compared to girls with ADHD were observed (p = 0.01). For the Hit RT SE, the ADHD groups obtained higher scores and, specifically, boys with ADHD obtained significantly higher scores compared to TD boys (p = 0.016) and to TD girls (p = 0.037). The analysis of Hit RT Block change revealed that boys with ADHD obtained a higher score compared to girls with ADHD (p = 0.024) but no difference appeared between girls and boys in the TD group. The same pattern of results occurred with Standard Errors for reaction time over Blocks (Hit SE Block change). Boys with ADHD displayed larger scores compared to girls with ADHD (p = 0.004) and to TD girls (p = 0.003). A main effect of diagnostic was found for the Standard Error of reaction time slope over different interstimulus intervals (HIT SE ISI change); youth with ADHD demonstrated less consistency compared to TD groups (p = 0.006), a tendency more acute in boys with ADHD. The ACT analysis revealed a lesser performance for the groups with ADHD (p = 0.013) but no sex difference nor interaction between sex∗diagnostic group was observed. No subtest of WCST was statistically significant in terms of group differences   varied bxibility . Analysip = 0.003) and faster RT per hit (p = 0.008) compared to the group with ADHD. For the INCO condition, the TD group demonstrated marginally faster RT Inco/Hits compared to the ADHD group (p = 0.073). Although neither sex nor interaction effects were found, boys with ADHD showed systematically longer reaction times compared to girls with ADHD.Behavioral performance results are presented in Cerebral activation findings are presented in Our expectations that ADHD boys would demonstrate more deficits than ADHD girls in sustained and selective attention and in cerebral activation during forethought were partially supported by the present study. Indeed, ADHD boys expressed greater inattentiveness, greater impulsivity, and lesser vigilance than TD boys, while ADHD girls did not differ from TD girls. Boys with ADHD also showed greater variability. Overall, WM capacities were lower in ADHD relative to TD group, confirming previous reports , 10. MorThe ADHD participants showed a tendency to be slower, but as accurate as the TD group on the forethought task. The forethought slowness was apparent especially in boys and was coherent with the CPT findings. As expected, extensive brain activation was observed in the TD group, including parietal and prefrontal regions as well as part of the cingulate gyrus and the cerebellum, during the forethought task performance. In contrast, the ADHD group showed no neural activation during forethought. This finding is consistent with reports of attenuated cerebral activation in ADHD tapping cognitive control , 27, worTD boys showed more extensive bilateral frontal activation relative to boys with ADHD, including the premotor cortex and the supplementary motor area (SMA). Our results are compatible with findings observed in TD adolescent groups , 19, 28 TD boys also exhibited greater activation in the bilateral parietal cortex, left IPL and right SPL, relative to ADHD boys. The SPL is involved in visual representation of movements  and in WFurthermore, boys with ADHD were found to hyperactivate a region adjacent to the medial temporal lobe, which is a part of the default mode network (DMN). This region was previously found to be hyperactivated in children with ADHD . FluctuaTD girls demonstrated widespread cerebral activation and there were no differences found for the ADHD girls > TD girls contrast. TD girls activated large portions of the cerebellum (culmen), a region activated in response to temporally unexpected stimuli . There iTD girls also activated the claustrum, a region highlighted by Dickstein et al. (2006)  as beingHowever, to fully establish the primacy of cerebral dysfunction in ADHD, future studies will need to employ a more comprehensive examination of executive function, using tasks known to produce consistent patterns of activity in other regions considered putative sources of dysfunction. Because the forethought task produced specific patterns of activity in boys and girls, our paradigm seems promising in further exploration of sex differences in the neural correlates of ADHD. Recent advances in brain imaging technology  allow us to examine more precisely and directly the relationships between brain regions during a cognitive task. A closer examination of the brain functional and anatomical connectivity would help in identifying entire neural networks underlying cognitive deficits in ADHD. Future research, including girls in the field of ADHD, promises exciting results linking the genomic, structural, and functional changes in the brain of individuals with ADHD. Advances in understanding of the ADHD neurobiology will hopefully help in developing new psychotherapeutic interventions and in identifying more targeted pharmacotherapies so that child psychiatrists can better manage their patients.In conclusion, the present findings point to greater EF deficits in boys compared to girls with ADHD. Moreover, boys with ADHD exhibited cerebral hypoactivation in the frontoparietal network. On the other hand, they hyperactivated cerebral regions linked to motivation. Taken together, these findings indicate that boys with ADHD show decreased attention processing that seems compensated by the use of supplemental motivation to perform as accurately as their TD counterparts. However, this compensation comes with a time cost. Girls with ADHD displayed more dispersed decreased neural activation in the frontocerebellar and frontoparietal systems compared to the TD girls. This suggests that they rely on different circuits to make decisions about incongruent situations with a related time cost. Overall, the present study supports the hypothesis of different neuropsychological and neurofunctional profiles in boys and girls with ADHD. This brings to light the importance of considering both genders while investigating ADHD in order to better understand the disorder and propose clinical intervention more specific to the gender.


The literature has suggested timing processing as a potential endophenotype for attention deficit/hyperactivity disorder (ADHD); however, whether the subjective internal clock speed presented by verbal estimation and limited attention capacity presented by time reproduction could be endophenotypes for ADHD is still unknown. We assessed 223 youths with DSM-IV ADHD (age range: 10-17 years), 105 unaffected siblings, and 84 typically developing (TD) youths using psychiatric interviews, intelligence tests, verbal estimation and time reproduction tasks  at 5-second, 12-second, and 17-second intervals. We found that youths with ADHD tended to overestimate time in verbal estimation more than their unaffected siblings and TD youths, implying that fast subjective internal clock speed might be a characteristic of ADHD, rather than an endophenotype for ADHD. Youths with ADHD and their unaffected siblings were less precise in time reproduction dual tasks than TD youths. The magnitude of estimated errors in time reproduction was greater in youths with ADHD and their unaffected siblings than in TD youths, with an increased time interval at the 17-second interval and with increased task demands on both simple and difficult dual tasks versus the single task. Increased impaired time reproduction in dual tasks with increased intervals and task demands were shown in youths with ADHD and their unaffected siblings, suggesting that time reproduction deficits explained by limited attention capacity might be a useful endophenotype of ADHD. Attention-deficit/hyperactivity disorder (ADHD) has been recognized as an early-onset, common neuropsychiatric disorder with deficits in a wide-range of neuropsychological functions . DespiteA useful endophenotype meets the following criteria : First, Many studies have shown that several neuropsychological functions  includinIn time discrimination, participants usually need to compare two brief intervals of similar duration in milliseconds , 15. SevOne previous study found that children with ADHD and their unaffected siblings were impaired in time reproduction tasks (at 4–20s), and suggested that time reproduction deficits in seconds may be an endophenotype for ADHD . A limitSome studies have shown that individuals with ADHD had a fast subjective internal clock speed , 23, as In a time perception dual task paradigm, as participants perform simultaneous temporal and non-temporal tasks, different kinds of information may compete for the limited attention resources , 28. It Rommelse et al.  found thThe current study used verbal estimation to explore subjective internal clock speed , 20 and The sample consisted of 223 youths with ADHD , 105 unaffected siblings , and 84 typically developing (TD) youths . The youths with a clinical diagnosis of ADHD in childhood according to DSM-IV criteria were recruited from the Department of Psychiatry, National Taiwan University Hospital, Taiwan. The clinical diagnosis of ADHD was confirmed using the Chinese-language Kiddie epidemiologic version of the Schedule for Affective Disorders and Schizophrenia (K-SADS-E) interview  of the pWe recruited 141 biological siblings, aged 10 or older, who were assessed for their lifetime and current diagnosis of ADHD and other psychiatric disorders using the Chinese K-SADS-E interview at a mean age of 12.7 ±2.4. The inclusion criteria for the unaffected sibling group included the participants who were the biological siblings of youths with ADHD, who did not have lifetime or current diagnosis of ADHD according to the DSM-IV ADHD diagnostic criteria as assessed by the Chinese K-SADS-E interview with the participants and their parents/caregivers, who were aged 8–18, and who and whose parents provided written informed consent to the study. For those families with two or more unaffected siblings, the siblings who have the closest age to the probands would be recruited. Of the 141 biological siblings, 36 (25.5%) were diagnosed either as ADHD or sub-threshold ADHD (more than three of nine symptoms in each of the DSM-IV inattention and hyperactivity-impulsivity dimensions) and 105 who did not have lifetime and current diagnosis of ADHD were identified as unaffected siblings.The TD youths were recruited from the same school districts as the youths with ADHD with the help of principals and teachers rather than by advertisement. They did not have lifetime or current ADHD based on the Chinese K-SADS-E interviews with them and their parents at their mean age of 12.7±1.9 .All children who had a lifetime clinical diagnosis of psychosis, autism spectrum disorder, or a learning disability or who currently had mood disorders, or who had an intelligence quotient score less than 80 were excluded.The Chinese K-SADS-E was prepared using a two-stage translation and modification of several items with psycholinguistic equivalents relevant to the Taiwanese culture, and further modified to meet the DSM-IV diagnostic criteria . It has Interviewer training: Four interviewers, who had undergone one year of intensive clinical and research training in child psychiatry before the Chinese K-SADS-E interview training, reached over 90% agreement on all mental disorders assessed by the Chinese K-SADS-E (ranging from 98.25±1.91 to 99.38±1.06) against the rating of each item in the K-SADS-E by SS Gau for 30 clinical subjects before study implementation. The inter-rater reliability of the Chinese K-SADS-E among SS Gau and the four interviewers using 12 subjects was satisfactory for all mental disorders, with generalized kappa for each diagnosis ranging from 0.86 to 1.00. Their K-SADS-E interviews were audiotaped periodically and monitored by SS Gau, who was blind to the personal information of the participants, to ensure the quality of interviews.Best Estimate Diagnoses: The corresponding author was blind to the diagnostic status and name of the participant and was not involved in the direct K-SADS-E interviewing of any of the participants or their parents at follow-up. She made all the best estimates of each psychiatric diagnosis according to the data from the K-SADS-E interviews of participants and their mothers, medical records, and other self-administered questionnaires reported by the participants, parents, and teachers. The diagnostic coding was categorized into definite , probable , possible (some symptoms but no impairment), and no diagnosis. For mental disorders other than ADHD, those patients who received a rating as definite or probable by best estimate were categorized as having a particular mental disorder.The CPRS-R:S, a 27-item parent-reported rating scale, consists of three factor-derived subscales  and the ADHD index . Each itTime perception tasks were computerized and controlled by the Visual Basic 6.0 Software Package on an IBM laptop (ThinkPad R51). The joystick made for PS2 was used as the input instrument.Verbal estimation Task: Participants first heard a computer’s sound like /bi/ (lasting 100ms from the computer) followed by the presence of a green circle with a diameter of 1.8 cm in the center of a blank screen visible for 5, 12 or 17 seconds. Immediately following each presentation the screen went blank and participants were instructed to verbally estimate the duration of the green circle and respond by a number key on the keyboard. After two practice trials, there were six presentations, two trials for each of three time intervals, 5, 12, and 17 seconds, appearing in random order.Time Reproduction Task-Single Version: The temporal stimulus was identical to that for the verbal estimation  of the Arabic numerals was randomly distributed, ranging from 1100 msec to 1800 msec in each trial so that the number of appearances of digits in each trial was not the same, even at the same time intervals , were interviewed using the Chinese K-SADS-E independently by separate well-trained interviewers to determine the diagnosis of ADHD and other psychiatric disorders as described by the DSM-IV diagnostic criteria. The participants were assessed using the Wechsler Intelligence Scale for Children-3rd edition (WISC-III), and only those participants who met the inclusion criteria were assessed with the time reproduction tasks. The participants who took methylphenidate were asked to halt medication for at least 24 hours before the tests.The Research Ethics Committee of National Taiwan University Hospital [IRB ID: 9561703011; ClinicalTrials.gov number p values in post hoc analyses. Cohen’s d was used to compute the effect size [We used SAS 9.2 software  to perform the data analysis. The descriptive results were displayed as frequency and percentage for categorical variables, and mean and SD for continuous variables. We used a multi-level model with random and fixed effects to address the lack of independence of youths with ADHD and their unaffected siblings within the same family, the repeated measures at different time intervals, and the different versions of tasks by the same participants. The Proc Glimmix procedure with binomial distribution and logit link for the non-linear mixed model was used to compare the rates of co-morbid psychiatric disorders and to compute the odds ratios and 95% confidence intervals. We excluded the outliers beyond 3 SDs for each condition of the time perception tasks. The Proc Mixed procedure was used with the linear mixed model to address the lack of independence within the same family for probands and unaffected siblings and the repeated measures within the same participants, and to compare each version of the time perception task. The three comparison groups were treated as a fixed factor and the three time interval lengths as repeated measures; the Bonferroni method was used to adjust ect size .In order to examine the effect of attention allocation in time reproduction paradigms, a linear mixed model with fixed and random effects was used to address repeated measures for the same participants. The three comparison groups were treated as a fixed factor, the three time interval lengths and three different tasks as repeated measures, and parental educational level and participants’ gender, age, full-scale IQ, use of methylphenidate, presence of psychiatric co-morbidity, and symptoms of ADHD as measured by the CPRS-R:S as covariates in the multivariate analysis. Two-way interaction terms including “groups and interval lengths interaction”, and “groups and different versions of time reproduction task” were also included in the multivariate analysis.Pearson’s Correlations were performed to explore the associations between the performance of verbal estimation, time reproduction , and the symptoms of inattention, hyperactivity and impulsivity as measured by the CPRS-R:S. Exploratory stepwise regression analyses were then performed to determine which symptoms  as measured by the CPRS-R:S accounted for the most variability in each time perception task.There were significant differences in gender, level of parental educational, inattentive symptoms and hyperactivity-impulsivity symptoms among the three comparison groups . One hunt(764) = 3.78, p< .001) and TD youths (t(764) = 4.21, p< .001), and the significant effects remained after controlling for covariates. The precision decreased with increased interval length, but the interaction effects between the groups and intervals were not significant (ADHD probands had more absolute discrepancy errors than unaffected siblings (nificant .t(764) = 6.37, p< .001) and TD youths (t(764) = 4.67, p< .001) which implied that they tended to overestimate the length of duration. The significant effects remained after controlling for covariates. The accuracy coefficient scores did not significantly change with increased interval length and no significant interaction effects were found between the groups and intervals.ADHD probands had higher accuracy coefficient scores than unaffected siblings (t(858) = 3.65, p< .001) and TD youths (t(858) = 2.53, p = .035), but the significant effect disappeared after controlling for covariates. The precision decreased with increased interval length, and the interaction effect between the groups and intervals was significant, suggesting a significant difference among the groups with increased interval length  = 3.79, p< .001 for the simple version; t(786) = 4.06, p< .001 for the difficult version) and unaffected siblings (t(778) = 2.58, p = .030 for the simple version; t(786) = 2.80, p< .016 for the difficult version) had more absolute discrepancy errors than did TD youths after controlling for accuracy rates in the non-temporal tasks in the two versions of the time reproduction dual tasks, but only the significant difference between ADHD probands and TD youths remained after controlling for covariates in the simple (t(655) = 3.18, p = .002) and difficult (t(663) = 2.68, p = .022) versions of the time reproduction dual tasks. The precision decreased with increased interval length and the interaction effect between the three groups and intervals  = 22.48, p < .001), and between unaffected siblings and TD youths in interval lengths  = 6.60, p = .010). There were contrast effects between youths with ADHD and TD youths in task design  = 5.83, p = .016; difficult vs. single, F = 9.84, p = .002); and between unaffected siblings and TD youths in task design  = 6.22, p = .013; difficult vs. single, F = 5.06, p = .025). The results showed that increased length of time intervals and task difficulty and complexity were associated with an increased magnitude of estimation errors among youths with ADHD and their unaffected siblings when compared to TD youths, after controlling for all the covariates.In order to compare the interactions between the three groups and the levels of difficulty in the time reproduction tasks  in absolute discrepancy scores, a mixed model was used to account for intra-family correlations and repeated measures in the same subjects . The bacr) between inattention and hyperactivity-impulsivity as measured by CPRS-R:S and the absolute discrepancy errors and accuracy coefficient scores for verbal estimation and the three kinds of time reproduction tasks     . Moreovep < .05)  and low p < .05) .2 .As shown in To the best of our knowledge, the current study was the first to examine verbal estimation and time reproduction performance with different levels of cognitive demands in temporal tasks using additive methods  in a larAlthough impulsive behaviors are essential symptoms of ADHD , past stOur finding that accuracy coefficients on verbal estimation were not impacted by the length of intervals, but that accuracy coefficients on time reproduction dual tasks decreased as the length of intervals increased suggested that time reproduction might have a different timing process compared to verbal estimation. One possible explanation would be that, in verbal estimation, participants transformed the monitored duration into the subjective timing unit with verbal labels ; howeverIn terms of absolute discrepancy errors, we found that ADHD probands and unaffected sibling performed worse as the length of the interval increased . The timThe time reproduction dual task requires great attention capacity , and priThere are some major methodological limitations to the current study. First, the clinic-based sample of ADHD probands may introduce selection bias and our findings may not be able to be generalized to community-based samples. Second, the ratio of gender in unaffected siblings was significantly different from the gender ratio in ADHD probands and TD youths. This made generalization of our results questionable; however, gender did not have an effect on the performance on the time perception tasks in all participants , and genSeveral studies have shown ADHD to be associated with deficits in different timing functions in seconds , and RomS1 Fig(DOCX)Click here for additional data file.S1 Table(DOC)Click here for additional data file.S2 Table(DOC)Click here for additional data file.S3 Table(DOCX)Click here for additional data file.S4 Table(DOCX)Click here for additional data file.S5 Table(DOCX)Click here for additional data file.


The term compensation is widely used in the context of attention deficit hyperactivity disorder (ADHD), yet, it is neither defined nor theory driven. Adapting a model of psychological compensation  to fit A The first prerequisite is defined by a deficit or mismatch between skill and environmental demand. This occurring mismatch could either be caused by an intraindividual decline in skill  or by increasing environmental demands . The second prerequisite states that an individual is aware of the mismatch; and the third prerequisite requires that an individual decides to compensate. If those prerequisites for compensation are fulfilled, the mismatch between skill and environmental demand can be counterbalanced by either the investment of more time/effort , or the utilization of latent  skills, or the acquisition of new skills. This process of psychological compensation can be adaptive or maladaptive, as it might not only lead to a reduction of the mismatch between skill and environmental demand but to other consequences as well . Note, that according to this definition social support or seeking a more supportive environment is not regarded as psychological compensation, since both change  the environmental demand and thus directly affect the deficit .The theoretical framework of psychological compensation  has beenThe first prerequisite of psychological compensation is the existence of a deficit that represents a mismatch between skill and environmental demand. As the impairment criterion  has to bFigure 2): at a neurobiological level  we are referring to is important, as deficits in individuals with ADHD have been conceptualized at different levels  and the compensation by more effort  are measured by the same variable  it is impossible to draw conclusion about which of both is related to the outcome . The second form of compensation, the utilization of latent but inactive skills is for instance shown when a student compensates for the ADHD symptoms (deficit) by high motivation (compensation) to avoid academic failure (outcome) . The thioutcome in order to clarify that the deficit and the outcome cannot be confounded . To draw sound conclusions, the deficit (independent variable), compensation (independent variable), and the outcome (dependent variable) need to be measured as three distinguishable variables. Outcome is usually measured on a higher level compared to deficit and compensation . A deficit in one study  can be the outcome in another study.To overcome the difficulty of being precise with regard to which deficit a study about compensation in ADHD is referring to, the first adaptation to the framework is the introduction of the term The second prerequisite states that an individual is aware of the mismatch between his/her skills and the environmental demands; whereas the third prerequisite entails that the person decides to compensate. Only very few studies have asked participants with ADHD about how they actually evaluate their own performance although it would be of greatest importance to investigate whether individuals are aware of their own deficits . There aTherefore, the second adaption is that a person with ADHD might not be aware of the deficit and might not have come to the decision to compensate deliberately. This adaptation seems of particular importance for studies at a neurobiological or psychological process level.Distinguishing adaptive and maladaptive consequences of compensation is pivotal. Psychological compensation can prevent diagnosis of ADHD because it allows individuals to meet environmental demands although they still show deficits. If psychological compensation is adaptive and does not have negative consequences, this is highly desirable and it would be unnecessary to diagnose or treat the individual. However, if psychological compensation is maladaptive, as for example in cases where individuals invest extensive effort and time to meet educational demands and neglect social relationships, it can lead to an accumulation of other comorbid problems in addition to ADHD . In thisAlthough consequences were already part of the original framework, they are of crucial importance for ADHD research. If the consequences are adaptive, the compensatory behavior could be promising for future interventions. However, if the consequences are maladaptive it is important to consider compensatory behaviors when diagnosing ADHD as they could disguise deficits in diagnostic procedures.Figure 2). Therefore, a nonexistent group difference is a necessary but not sufficient condition to infer compensation. In order to draw conclusions about compensation, we need to measure deficit, compensation, and outcome independently and demonstrate that compensation leads to nonexistent group differences. Thus, we need to assess deficit and compensation as two separable independent variables and outcome as the dependent variable. In addition, we need to show that the deficit is stable  and that the compensation entails equal or better outcome despite the deficit.Most studies of psychological compensation generate hypotheses instead of testing them. Results from cross-sectional studies comparing samples with and without ADHD not showing any differences or an even better performance in the ADHD sample can generate ideas of psychological compensation. However, to test hypotheses about psychological compensation in ADHD, we need to reveal that the deficit remains and that it really is compensation leading to nonexistent group differences. If compensation is successful, it will hide deficits at the next level  one will never be able to answer questions about compensation. Instead, compensation in ADHD can either be investigated in between-person designs of samples with the same deficit but various outcomes or longitudinally in within-person designs and naturally or experimentally varying environmental demands.In summary, for the study of psychological compensation in ADHD we need a clear definition and operationalization of the deficit we are referring to, the compensation and the outcome. We need to include groups with ADHD that are not able to meet environmental demands, a group with ADHD that is able to meet environmental demands, and a group without ADHD that is capable of meeting environmental demands.Research on ADHD benefits from studying compensation, because compensation might hide a core deficit of ADHD. As a result, some individuals with ADHD do not receive a diagnosis resulting in underdiagnosis, especially in females . Such anThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.