Quantitative studies in motivation. I. Strength of conditioning in rats under varying degrees of hunger

Four equated groups deprived of food for intervals, respectively, of 1, 12, 24, and 48 hours were conditioned, in the Skinner apparatus, to depress a bar for food. They were then fed. 48 and 78 hours later they were given extinction tests under conditions of 24-hour food deprivation. The measures of conditioning strength were (1) number of extinction responses and (2) total time of extinction. In terms of both criteria, conditioning strength rose from a low point 1 hour to a high point 12 hours after feeding. There was a fairly rapid decrease in strength between 12 and 24 hours after feeding. A smaller decrease occurred between the 24- and 48-hour intervals. On the basis of variability data it is suggested that "drive in excess of the optimal (12-hour privation interval) may impair acquisition through decreasing variability of response." Extensive bibliography.