referring now to fig1 , a portable eye tracking unit 10 that determines the gaze direction 12 of test subject 14 is coupled to a processor 16 which not only drives an icon 18 on a screen 20 , it also detects the direction of gaze of test subject 14 as illustrated at 22 . the construction of such an eye tracking device is described in u . s . patent application ser . no . 13 / 507 , 991 filed aug . 10 , 2012 and determines when the direction of gaze 12 impinges on the moving icon , which in the indicated case moves in a circle as indicated by arrow 24 . the ability to track the icon is determined at 26 which in essence measures the cognitive performance of the test subject by determining the test subject &# 39 ; s ability to have his or her eyes track the moving icon . as described in the aforementioned patent application the ability to track the icon is often times measured in terms of the lag time or lead time of the individual &# 39 ; s eyes in tracking the icon , called anticipatory timing . a particularly good metric for determining the ability to track the icon is the variability in the anticipatory timing or , more particularly , the regulatory of the anticipatory timing . regardless , a measure of the cognitive performance of test subject 14 is applied to a peak cognitive performance measurement unit 30 , the operation of which will be described hereinafter . while the cognitive performance of an individual is tested utilizing eye tracking , as illustrated in fig2 the ability to track a moving icon 32 on a tablet 34 that traverses a path illustrated by dotted line 36 measures cognitive performance as illustrated at 38 . in order to perform the peak cognitive performance measuring , the success of following icon 32 is determined at unit 40 in much the same way as the eye tracking system of fig1 . in this instance the pressure of the hand 42 on tablet 34 provides an indication of the position of the end of finger 44 on tablet 34 . to the extent that this position registers with the current position of the moving icon 32 then one can measure cognitive performance though the ability of the finger to track the moving icon . note , this measures both eye tracking and manual dexterity at the same time . said two different processes are involved , the test is exceedingly robust . referring now to fig3 , how one measures the coincidence of gaze direction or finger position to a moving icon is shown . here a display 50 is shown in which a moving icon 52 traverses a path illustrated by dotted line 54 . this path is used to promote smooth eye tracking determinations . the result of the tracking is processed by processor 56 to which a motion algorithm 58 is applied , with processor 56 driving display 50 and icon 52 thereon . it is important note that the degree of difficulty of the test depends upon the motion of the icon and the path that it traverses . for instance , a circular motion which is repetitive is easy to anticipate and therefore is the least difficult test for smooth eye pursuit . one can however produce more than circles on display 50 and the more complicated the path 54 the more difficult the test . thus , motion algorithm 58 is capable of producing variable difficulty in the test presented to the test taker . as illustrated at 58 as an output from processor 56 a unit determines how far off the target the eye gaze direction or the position of the person &# 39 ; s finger is and therefore establishes through the aforementioned anticipatory timing a level of cognitive performance . it will be appreciated that the maximum level of cognitive performance can be quantified in terms of when the individual cannot perform the test meaning he cannot track the moving icon . thereafter a threshold 60 can be set to indicate the maximum test difficulty that the individual can successfully complete . in order to measure the coincidence of either the gaze direction or the finger , one can find the path , find an instantaneous vector of movement of the icon , find a normal to the vector and thereafter find the arc path length between the icon and either the intercept of the gaze direction with the tablet or the finger position . having found the path arc length one can go about establishing anticipatory timing . regardless of the way that a measurement of cognitive performance is arrived at , it is the purpose of the subject invention to determine the peak cognitive performance . referring now to fig4 , in order to do so a cognitive performance measurement 62 is performed in any manner commensurate with either smooth eye pursuit or mechanical testing . as seen by module 64 a determination is made as to the maximum state of cognitive performance where a test subject fails the test . this unit also sets a maximum difficulty threshold meaning that test difficulty below this threshold enables the individual to successfully complete the test , whereas a test difficulty above this threshold is one in which the individual taking the test cannot successfully complete the test . the maximum difficulty threshold 66 determined in this manner is coupled to a unit 68 which oscillates the test difficulty about the maximum difficulty threshold . in order to oscillate the test difficulty the output from unit 68 is applied to a control unit 70 that changes the path movement of an icon on a screen to control test difficulty . this control unit is then coupled to a unit 72 that controls path motion in an ever increasingly or decreasingly difficult test . once having initiated the oscillating test difficulty algorithm what is then recorded at unit 74 is the peak cognitive performance during the oscillation . in one embodiment the peak cognitive performance is an average score for the test after a so - called stasis period has established a maximum difficulty threshold . at the bottom of fig4 is a series of paths 76 and 78 along which an icon 80 is to travel . there are various ways in which to increase the difficulty of a test , with the increase in difficulty being for instance an increase in the speed of the icon , an increase in the number of lobes of the path , an increase in the amplitude of lobes of the path or even a change in icon acceleration , with the difficulty referring to how easy or difficult it is for the individual to track the moving icon . referring now to fig5 , it is important to make sure that the moving icon position is not easily anticipated . here an icon 82 is moved to a position 82 ′ which goes along an irregular but smooth path 84 in the direction of arrow 86 . it is noted that if a non - regular path is presented to the test subject the irregular path takes out any learning effect . moreover , the particular shape allows the testing authority to vary the difficulty of the test for instance in terms of velocity , number of lobes , size of lobe and rate of curvature or indeed any of a number of different methods by which the ability to follow the moving icon can be made harder . it will be seen that the above offers a means to vary test difficulty such that the test can become harder and in which the difficulty can be easily regulated by the differing complexity of the path on which the icon is to be moved . referring to fig6 , what is shown is four different difficulties having to do with path configuration . here at difficulty i is shown by the slightly undulating path 90 which presents an icon traveling along this path . the difficulty in following the icon on this path is minimal even though the path is not easily anticipated . referring to difficulty ii , path 90 ′ is provided with an increased number of lobes here at 92 , 94 and 96 , with the number of lobes in a path determining the difficulty presented to the test subject . referring to difficulty iii , not only can the number of lobes 96 be increased dramatically , also the amplitude of the lobes can be varied such that an icon going along the paths established by these lobes will move either more or less , thus giving the test taker a challenge to be able to track the moving icon as it travels along these paths . finally with respect to difficulty iv it can be seen that the velocity of the icon illustrated by arrow 98 can be of one magnitude as it moves around a lobe 100 , whereas the velocity of the icon as it moves along a straight path stretch as illustrated by arrow 102 can be less . finally the velocity of the icon illustrated by arrow 103 may be different than the velocity illustrated by arrow 98 as the icon moves around another lobe 106 , such that different icon accelerations can be presented to the test taker . as a result the test difficulty can be varied in a number of different ways from a less difficult test to a more difficult test , thereby to provide different test difficulties for the subject taking the test . referring now to fig7 , what is shown that the test is administered in one embodiment in a number of phases . phase i relates to the initiation of the test in which initial matching is detected for a prescribed set of path motion . here the test difficulty is either held constant much as illustrated at 110 . after initialization such that the individual is comfortable in taking the test , there is a calibration phase . this is shown by the slight variation of test difficulty . thereafter in phase ii the test difficulty is ramped up significantly as illustrated 112 until such time as the patient or test taker is unable to perform the test as illustrated at 114 by a line 116 that denotes the point at the end of phase ii that establishes a threshold . thereafter as illustrated at phase iii the test difficulty is varied very little as illustrated at 118 to provide a stasis period to be able to stabilize on the cognitive ability of the test taker . at the end of phase iii the cognitive ability of the test taker is ascertained and more particularly his maximum ability to achieve . for phase iv the test difficulty is oscillated around this threshold level as illustrated at 120 . all the time that the tests are being performed in varying degrees of difficulty the test taker is scored and the scores are presented as illustrated in fig8 . here it can be seen that during phase i the score of the test taker improves as he gets used to taking the test as illustrated by line 122 . thereafter when the test difficulty is ramped up the score 124 decreases to a failure at a threshold point as illustrated at 126 . this failure threshold point is utilized in establishing when the individual is in a relatively stable mode or in stasis , and this is illustrated by the test score illustrated by line 128 . upon reaching stasis , the test difficulty is oscillated around the aforementioned threshold and the test score as illustrated by line 130 reflects this such that the test scores reflect oscillation in difficulty just below the threshold level . the average during oscillation provides an accurate indication as to the peak cognitive performance capabilities of the test taker . it is because one is able to make accurate initial cognitive performance measurements and then to vary the difficulty of the test and oscillate the difficulty around a threshold that the average trace measurement is a valid indicator of peak cognitive performance . referring to fig9 , having ascertained peak cognitive performance , this metric can be used over time to measure a decreasing trend of cognitive impairment with age . here cognitive peaks 140 , 142 and 144 taken at 10 gear intervals indicate a decreasing cognitive performance trend indicated by dotted line 146 . when this trend is compared with a baseline range 150 one can predict when cognitive performance falls below the baseline range as illustrated at 152 . the steepness of trend line 146 is oftentimes a good predictor of the presence of a mental condition such as dementia or alzheimer &# 39 ; s disease . one could predict the likelihood of later life alzheimer &# 39 ; s disease or its onset by establishing the subject peak cognitive performance trend . the ability to accurately keep track of peak cognitive performance has many uses in both diagnostics and for instance the efficacy of cognitive enhancement drugs , with trend lines indicating improvement in cognitive performance when using such drugs . in short , an accurate robust measure of peak cognitive performance opens up many avenues for evaluation and are all due to the ability to robustly measure peak cognitive performance through smooth pursuit tracking and the ability to vary test difficulty . the mathematical definitions of the metrics used herein are presented below : the standard deviation of the sum of the absolute value of a set of target position arrays subtracted from a set of user position arrays . n = the length of the target position ( the number of elements in the array ). j = the standard deviation index for the absolute value target minus user array i = the index for the sum of absolute value target minus user array the variance of the standard deviation of a set of target position arrays subtracted from a set of user position arrays . n = the length of the target position ( the number of elements in the array ). finding the minimum of the application of the sum of an error array on a delta distribution . n = the length of the target position ( the number of elements in the array ). ƒ ( t + 1 )= kf ( t − n , t 0 ) a factor of k applied to any function listed on this sheet . while the present invention has been described in connection with the preferred embodiments of the various figures , it is to be understood that other similar embodiments may be used or modifications or additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom . therefore , the present invention should not be limited to any single embodiment , but rather construed in breadth and scope in accordance with the recitation of the appended claims .
a method to determine the subject &# 39 ; s peak cognitive performance using smooth pursuit tracking tests . the method utilizes instantaneous performance feedback to accurately quantify the subject &# 39 ; s peak cognitive performance by changing the difficulty of the test in response to the subject &# 39 ; s performance .