Thinking is for doing Individual differences in working memory inattention and goal neglect errors
International Symposium on Executive Function in the Mind: Kyoto, 5 6 December 2007 Explorations of task set control through experiments on task switching. Stephen Monsell, School of Psychology, University of Exeter, UK A major constituent of executive function is the ability to get the mind into such a state that we perform one cognitive task rather than one of the many others that may be afforded by the current input and contents of memory. "Task set" simply labels the complex of settings that comprise such a state (orientation of attention, activation/inhibition of responses, of S R rules, of inter domain links, etc. If we practice a task, the task set becomes readily retrievable from memory as a package. Our task set state at any moment reflects a complex interaction between "endogenous" (top down, intentional) control reflecting goals, intentions, motivation and exogenous (bottomup, stimulus driven) activation of responses and stored task sets by the stimulus, modulated by the frequency with which task sets have been exercised and the recency with which they have been active. The properties of task set control mechanisms are most likely to be revealed in behavioural or brain activation measures at points where we must change tasks or anticipate changing tasks. This is the rationale for task switching experiments. Subjects respond on each trial to a stimulus with a discrete response, according to a task rule (usually some sort of classification, or identification, of one attribute of the stimulus, such as its colour, shape, or value) Usually only two or three tasks are "in play" through the experiment. The task required on each trial is indicated by task cues, a prespecified task sequence, or both. Performance is generally worse in sequences of trials in which there are task switches compared to sequences in which there are not "mixture costs" In the mixed task blocks continuing activation of currently irrelevant task sets is indicated by elevated Stroop like response conflict effects. On a trial where the task changes there is marked slowing of the response (a "task switch cost" and conflict effects may also be magnified. The switch cost is typically reduced by allowing half a second or so to prepare for a change of tasks, but is rarely eliminated there is usually an asymptotic "residual" cost even with several seconds allowed for preparation. (See Monsell, 2003, for review) Early hopes that switch costs might measure endogenous control processes or exogenous influences in a relatively direct way have given way over the last decade to the realisation that their causation is complex. This of course has implications for attempts to study the development of executive function using switching paradigms. I will address some recent controversies, illustrated by data from our lab. The ability to reduce switch costs through advance preparation has been taken to isolate the contribution of endogenous "executive" control processes to switch costs. But how control is reflected in behavioural measures, and whether we can detect neural correlates of this preparation process, remain problematic issues. It has even been argued that the reduction in switch costs through preparation in task cuing experiments can be explained entirely in terms of simple associative processes, without appeal to endogenous control. I will briefly review the current state of play. Another controversial issue concerns the contribution to switch costs of competition due to carry over of task set states from previous trials. One theory is that task set states simply persist transiently "task set inertia" causing competition on the first trial (or so) following activation of a different task set, then being suppressed by actual performance of the different task (but not by mere preparation for it) Another theory is that through associative learning, stimuli activate task sets with which they have recently or frequently been associated, and this has more impact on switch trials (perhaps because of instability due to task set inertia) I will present some recent data from our lab where we find strong effects of recent stimulus task associations, but they do not modulate switch costs. Because the majority of task switching experiments have used stimuli that afford responses in more than one of the tasks in play, it is sometimes thought that task switch costs arise chiefly as a result of having to cope with response conflict. I'll show that substantial costs are observed even when the currently irrelevant stimulus attribute is never associated with a response. Also, contrasts between such single affordance stimuli and congruent stimuli (i.e. mapped to the same response in both tasks) can reveal conflict at the level of task sets. Monsell S, (2003) Task switching. Trends in Cognitive Sciences, 7 (3) 134 140. Contact Address: Stephen Monsell Ph.D. Professor of Cognitive Psychology School of Psychology University of Exeter Exeter EX4 4QG England Phone: +44 (0)1392 264647 Fax: +44 (0)1392 264623 Email: S.Monsell@exeter.ac.uk International Symposium on Executive Function in the Mind: Kyoto, 5 6 December 2007 The role of verbal short term memory in task switching and action control Satoru Saito, Graduate School of Education, Kyoto University, Japan Flexibility in human behaviour is secured by executive control, which enables us to regulate our mental activities endogenously against prepotent responses or habit. In this talk, I will first provide evidence for the involvement of verbal short term memory in executive control that emerges through task switching paradigms. A typical switching paradigm requires participants to repeat the same task or to switch between two tasks in separate blocks or in the same block. The cost of switching the difference in performance (response times and errors) between the repeated and switched trials is arguably thought to reflect executive demands required in preparation for task switching. A seminal study by Goschke (2000) suggested that the preparation for task switching is supported by the retrieval of a verbal task representation. He found that the switch costs in response times were greater under conditions in which participants were required to say a task irrelevant word once during a long response stimulus interval (i.e. 1500 ms) than under conditions in which participants were required to say the next task name once. Since articulation of a task irrelevant word (called articulatory suppression) seemed to prevent participants from retrieving or retaining verbal representations of task information, Goschke (2000) suggested that an important component of preparing for task switching was the use of task representations that could be in verbal format, such as self instruction. Subsequent studies examined the cost of switching in a variety of task switching paradigms systematically, using an articulatory suppression technique, in order to clarify the roles of verbal short term memory and inner speech in task switching, and to explore the nature of verbal executive control (Baddeley, Chincotta, and Adlam, 2001; Emerson Miyake, 2003; Miyake, Emerson, Padilla, Ahn, 2004; Saeki Saito, 2004a, 2004b; Bryck, Mayr, 2005; Saeki, Saito, Kawaguchi, 2006) Based on this, the literature suggests two possible roles for verbal short term memory in task switching paradigms, or more generally, roles for verbal short term memory in action control: Miyake et al. (2004) proposed that task set retrieval is an important function of verbal short term memory (inner speech in their paper) using the random cueing paradigm. Saeki and Saito (2004b) and Bryck and Mayr (2005) suggested that serial order control is a crucial function of verbal short term memory in action control, through the alternating runs paradigm introduced by Rogers and Monsell (1995) We assume that task set retrieval requires reconstruction of task set binding, which includes the binding of task components (e.g. stimulus response mapping is a type of bound information) and that serial order control includes the retention of task order and the resolution of order conflict between two tasks. Based on this theoretical framework, which consists of the concepts task set binding and serial order control, we are now examining the role of verbal short term memory in motor action control, using an action slip induction technique (Mattson Baars, 1992) The slip technique produced many action spoonerisms and other types of action slip, and the former increased dramatically when either articulatory suppression or body movement suppression was performed concurrently, while other slips increased only in the movement suppression condition. Articulatory suppression seems to be able to induce action slips by either weakening action binding or interfering with serial order control for action sequences, but not by disrupting the memory of the action components. The results suggest a direction for research on verbal regulation mechanisms in a variety of human behaviours, through which we can integrate studies on working memory, task switching, and executive control.