7. Task Dependence of Perceptual Deadzone

In this chapter, we study whether the perceptual deadzone depends on the task to be performed during the psychophysical experiments. In order to study this, we design a psychophysical experiment where we define two specific tasks: discriminative and comparative. In the discriminative task, the user must discriminate if the successive stimulus is different from the reference force, be it increasing or decreasing in magnitude. On the other hand, in case of the comparative task, the user has to discriminate the stimulus only along one direction, either increasing or decreasing in magnitude. Responses are recorded for both the tasks for several users. Support vector machine (SVM), a machine learning approach, is applied to the recorded responses to estimate the perceptual deadzone for each task. Our results demonstrate that comparative deadzone is significantly smaller than the discriminative deadzone in terms of their width and the just noticeable difference, suggesting that the task of discriminating two forces is more difficult for a user than to compare which force is greater (or smaller). Hence taking inference of this study, we demonstrate that the perceptual deadzone does depend on the task being performed.