The Amount and Direction of Change of Background Noise as a Conditioned Stimulus

Abstract

This thesis is concerned with intensity characteristics of conditioned stimuli in acquisition of a conditioned emotional response (CER) in rats. A comparison was made of CSs which differed (between groups) with respect to amount and direction of change in white noise from a constant background stimulation level. The measure of conditioning was the degree to which the CS disrupted ongoing, food-motivated, bar-pressing activity. The major findings were (1) that rate of conditioning was a monotonic increasing function of amount of intensity change in either direction; and (2) an increase in noise intensity from background X to CS Y produced more rapid acquisition of the CER than did a decrease from background Y to CS X. (3) During pretests, a noise increase produced a small, but reliable, Increase in rate of bar-pressing, while a noise decrease produced a slight suppression.