Behavioral Evidence in the Rat on the Question of Frequency Modulation and Amplitude Modulation

Abstract

This study was designed to test the ability of the Harvard strain of albino rats (three month old males) to make auditory discriminations between modulated and nonmodulated tones, based on differential responding in an instrumental conditioning situation. Rats trained to a criterion level of responding in a Skinner-box food-lever association were then subjected to modulated and nonmodulated tones of 4 kc at 70 db SPL. The tones were randomly arranged on tape to constitute a 3-min trial period. If the rat made the characteristic response during the time the tone was modulated, he was rewarded with a standard pellet. Responses during nonmodulated presentations of the tone were unrewarded. Beginning with examination of tones modulated at 5% in frequency or 5 db in amplitude, the study was planned so that the degree of modulation is progressively reduced till no discriminatory behavior is exhibited. The rat's performance in these stages of the over-all problem will be discussed. Comment will be made on the direction of further work in this area and its implications for the theory of primary auditory abilities. [This study is supported in part by Contract No. AT(30-1)-2398 of the U. S. Atomic Energy Commission.]