Psychophysical methods

Recall from Section 2.3 that psychophysics relates perceptual phenomena to the original stimuli, which makes it crucial for understanding VR. Stevens' power law (2.1) related the perceived stimulus magnitude to the actual magnitude. The JND involved determining a differential threshold, which is the smallest amount of stimulus change that is detectable. A special case of this is an absolute threshold, which is the smallest magnitude stimulus (in comparison to zero) that is detectable.

Psychophysical laws or relationships are gained through specific experiments on human subjects. The term psychophysics and research area were introduced by Gustav Fechner [77], who formulated three basic experimental approaches, which will described next. Suppose that $ x$ represents the stimulus magnitude. The task is to determine how small $ \Delta x$ can become so that subjects perceive a difference. The classical approaches are:

Although these methods are effective and widely used, several problems exist. All of them may be prone to some kinds of bias. For the last two, adaptation may interfere with the outcome. For the last one, there is no way to control how the subject makes decisions. Another problem is efficiency, in that many iterations may be wasted in the methods by considering stimuli that are far away from the reference stimulus.

Steven M LaValle 2020-01-06