Differential sensitivity to intensity as a function of the duration of the comparison tone.

Abstract

Three functions are presented for 2 Os showing the relation between the duration of the comparison tone and the intensity increment necessary to activate one additional neural unit. With change in the duration of the comparison tone, a ratio as large as 3 was found between the highest and the lowest [DELTA]I ratio in any one function. Three hypotheses to explain the form of the sensitivity function are presented and rejected as inconsistent with the obtained data. Among these is Crozier''s, which states that the thresholds of the neurons are normally distributed, and that any measure of the sensitivity of the organism should be the normal cumulative ogive when sensitivity is plotted as a function of the logarithm of time. This last hypothesis is rejected because the functions are not asymptotic to zero duration. Two possible explanations are presented: one in terms of a mechanical threshold, and another in terms of transient stimulus waves.