3 rhesus monkeys were obtained from the Regional Primate Center, University of Wisconsin. These animals had been subjected to total social isolation during their 1st yr. of life. 3 feral monkeys of the same age constituted the normal group. The animals were trained to perform an instrumental avoidance response to a visual stimulus. There were no differences in acquisition of the response either in terms of instrumental behavior or conditioned cardiac responses. The animals were then paired in all possible combinations for communication of affects tests using the cooperative-avoidance technique. The monkey which received the conditioned stimulus was visible to the animal having access to the response bar via closed-circuit television. The results, both instrumental and physiological, indicated that isolate monkeys were incapable of utilizing facial expressions of other monkeys in order to perform appropriate avoidance responses. The isolates also were found to be defective senders of facial expression.

A reversal shift (RS) or a nonreversal shift (NRS) of concept was learned by 80 college students after either criterion learning or overlearning of the first concept. 2 and 4 sorting categories were used. The wellestablished finding that, with 2 sorting categories, an RS is easier than an NRS was again observed, following criterion learning (p < .10) and following overlearning (p < .002). Also, in agreement with previous data, the RS was not easier than the NRS with 4 categories. Overlearning appeared to facilitate all shifts, although its effect on the 2category NRS was not statistically reliable. The results are examined in relation to an S-R mediational framework.

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