An apparent new instance of stimulus intensity dynamism during discrimination of duration of repeating auditory stimuli

Rats were trained on a VI/EXT discrimination using barpressing in a Skinner box for food reinforcement. The discriminanda consisted of different proportions of noise to silence within a fixed 3^-s noise-plus-silence repeating cycle. These stimuli were easily discriminated by human subjects, but the rats formed the discrimination only poorly and after considerable training. Analysis of response rates during noise and silence separately within the 3^-s noise-plus-silence cycle showed higher response rates during noise, irrespective of whether this was during the positive or during the negative stimulus, or whether relatively long duration of noise or relatively short duration of noise (within the 3^-s cycle) constituted the positive stimulus. These results are seen as providing an instance of the dynamogenic effects of stimulus intensity on response vigour to which the Perkins-Logan generalization of inhibition hypothesis of stimulus intensity dynamism cannot apply.