Auto-Shaping in Rats to the Presentation of Another Rat Predicting Food

Rats direct social rather than eating behavior toward a stimulus rat that predicts the imminent delivery offood. This result suggests that a predictive stimulus does not become a substitutefor a reward, but its characteristics elicit and support a particular subset of the responses commonly related to that reward. them to approach and eat rapidly from the food tray when food was delivered. On the third day of pretraining, each subject received 30 10-second presentations of the stimulus rat. No food was delivered on this day. After the 11 acquisition sessions, all subjects received eight extinction sessions during which the predictive stimulus was presented as in acquisition, but no food was delivered. The behavior of the subjects in the presence of the predictive stimulus was recorded by an observer using a coding scheme modified from Peterson (10) and Grant and Mackintosh (8). On each presentation of the predictive stimulus the observer noted several behaviors, including: Orient, Approach, Sniff, Bite, and Social Contact (paw, groom, crawl-over, and anogenital sniff) (11). A reliability check of this coding scheme with a naive observer produced an average interobserver reliability of . 99. The four panels of Fig. I show the median percentage of trials on which each group of five animals performed behaviors in the different categories. The group data adequately reflect the scores of the individual subjects. Figure IA shows that the Cs+ animals successively increased the frequency of Orient, Approach, Sniff, and Social Contact during the I1-day acquisition period, and successively decreased the frequency of these behaviors during extinction. The incidence of Bite was zero over all trs. The CSS animals also engaged in considerable behavior directed toward the stimulus rat, but their performance stabilized at a lower level than that of the CS+ animals (see Fig. I B). Over the last 5 days of acquisition the median scores of the animals in each group showed no overlap in Social Contact, Approach, and Sniff, and only a single common score in the case of Orient. During extinction, the scores of the animals in the CS+ and CSS groups overlapped considerably. The CS+ animals showed greater diversity of social contact than did the CSS animals. Table I shows the median individual scores over the last five acquisition trials for paw, groom, crawl-over, and anogenital sniff. All five CS+ animals showed paw, groom, and crawl-over behaviors, and three showed anogenital sniff. Of the five CSS animals, three showed paw, two showed groom, and only one showed crawl-over and anogenital sniff. Video tapes of a randomly selected animal in each group showed additional social postures for the CS+ animal, such as sideways and head-over postures (8). In comparison to both the CS+ and CSS groups, the CSr groups showed a marked 4 inhibition of approach behavior during ac-4 14 NOVEMBER 1975 quisition (see Fig. IC). With one exception, the animals oriented on less than 10 percent of the trials and all animals remained by the food tray during the presentation of the stimulus rat. No animal ever engaged in Social Contact. During extinction all behaviors except Social Contact appeared to recover and increase toward overlap with the scores of the CSS group. The CSW group showed an increase in Orient equivalent to that of the CS+ group, but little increase in Approach or Sniff, and no Social Contact score (see Fig. 1 D). These results appear to reflect a low level of conditioning to the block of wood. The relative absence of Approach in this group shows that Approach to the predictive rat in the CS+ group was not based on its predictive value alone. Conditioned Approach