Psychophysics of Direct Remembering
K. Geoffrey White University of Otago, New Zealand
The traditional problem of psychophysics is the problem of scaling -- the quantification of relative stimulus effects on behavior. In the case of remembering, stimuli have their effect at a temporal distance. The problem is thus one of specifying how time modulates the stimulus effect. In the present chapter, I suggest that the action of temporally distant events is direct.
In a theory of direct remembering, the notion that the stimulus effect is direct follows J. J. Gibson's analysis of direct perception. Temporal distance may attenuate the stimulus effect in an analogous fashion to the attenuation of discriminability by spatial distance. In other words, the effect of the temporally distant event diminishes with increasing time in the same way that an event becomes difficult to distinguish with increasing spatial distance. This diminution function does not differentiate a time of perceiving from a time of remembering, in which case the rate of decrement must be constant. According to J. J. Gibson, "the traveling moment of present time is certainly not a razor's edge, as James observed, and no one can say when perception leaves off and memory begins ( 1966, p. 276)" (also see Gibson, 1979, p. 253; Turvey, 1974, 1977). Consequently the function relating forgetting to increasing time should fall off at a constant rate.
This "constant-rate" assumption of a theory of direct remembering is captured by supposing that the decrement in discriminability, Ω (log dt), that occurs over a small interval of time Ω (t), is proportional to discriminability at the beginning of the interval, log dt (Fig. 10.1).
The constant of proportionality is b (with units of t-1). The decrement in discriminability is