Psychophysics: The Fundamentals

The theory of signal detection has provided refined measures of the capacity of human observers to detect sensory stimuli. But in addition, by incorporating aspects of decision making, the theory provides many connections between psychophysics and other areas of psychology. Advances in psychophysical methodology are no longer restricted in their usefulness to the study of sensory thresholds, but instead may provide powerful techniques for studying how people make decisions about environmental events in general. For example, TSD has been useful in studying decision processes ranging from how clinicians diagnose illness from a set of symptoms to how people decide whether or not they have seen a person's face before. The research described below is but a small sample of the many applications of TSD to problems of determining how people make decisions.

The continuity-noncontinuity issue has a long history in several areas of psychology besides the study of sensory processes. The essential question, however, is always the same: do psychological processes change on a continuum, or do they change in discrete steps? For years, psychologists have been concerned with the problem of whether learning is an all-or- none or a continuous process. Does the learning curve represent a number of small discrete increments in learning, or does it represent a gradual and continuous change in the amount learned? A closely related problem

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