A test of the Pfanzagl bisection model in rats.

The bisection method of animal psychophysical scaling was examined as a measurement procedure. The critical assumptions of bisection scaling, as described by Pfanzagl (1968), were tested to determine if a valid equal-interval scale could be derived. A valid scale was derived in which subjective time for the rat was a power function of real time. Bisection points were found to be context dependent, because the spacing of stimuli significantly affected the bisection points. Such context effects were directly related to the size of the interval bisected, whereas measurement errors in estimates of the exponent of the power function were an inverse function of interval size.