Abstract
During psychophysical testing, a loss of concentration can cause observers to answer incorrectly, even when the stimulus is clearly perceptible. Such lapses limit the accuracy and speed of many psychophysical measurements. This study evaluates an automated technique for detecting lapses based on body movement (postural instability). Thirty-five children (8–11 years of age) and 34 adults performed a typical psychophysical task (orientation discrimination) while seated on a Wii Fit Balance Board: a gaming device that measures center of pressure (CoP). Incorrect responses on suprathreshold catch trials provided the “reference standard” measure of when lapses in concentration occurred. Children exhibited significantly greater variability in CoP on lapse trials, indicating that postural instability provides a feasible, real-time index of concentration. Limitations and potential applications of this method are discussed.
Highlights
IntroductionA loss of concentration can cause observers to answer incorrectly, even when the stimulus is clearly perceptible
During psychophysical testing, a loss of concentration can cause observers to answer incorrectly, even when the stimulus is clearly perceptible
CoPMAD was significantly greater on incorrect catch trials (Wilcoxon signed-rank; Z = 2.86, p = .004), meaning that children shifted their posture to a greater extent on trials where lapses in concentration occurred
Summary
A loss of concentration can cause observers to answer incorrectly, even when the stimulus is clearly perceptible. Such lapses limit the accuracy and speed of many psychophysical measurements. This paper considers how such measurements could be used to improve the accuracy and reliability of psychophysical estimates To make this inference we must assume, implicitly, that the observer’s responses are determined solely by their perception of the stimulus. Behav Res (2019) 51:28–39 lengthy and repetitive, and an observer’s mind may sometimes wander Such a lapse in concentration can cause the observer to forget, momentarily, what the required judgment is or how to respond appropriately. The observer’s response will be independent of the stimulus magnitude, and the probability of answering correctly on that trial will be chance (e.g., 50%, when the task is a twoalternative forced choice; 2AFC)
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