Contrasts in visual responsiveness and emotional arousal between rhesus monkeys raised with living and those raised with inanimate substitute mothers.

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Abstract
Rhesus monkeys [Macaca mulatta] were raised with dogs or inanimate surrogates in outdoor cages which provided them with complex, highly varied visual surroundings. Visual responsiveness to a variety of colored transparencies was investigated in 3 experiments, completed when the monkeys were between 18 and 30 mo. old. The frequency and duration of looking at slides was significantly higher for dog-raised than for inanimate-surrogate-raised monkeys and dog-raised monkeys were much more responsive to the novelty, complexity and mode of presentation of the stimulus materials. Measures of emotional arousal were obtained during the final experiment. Heart rate, vocalization and changes in plasma cortisol were higher for monkeys raised with dogs. The frequency of most self-directed behaviors, was higher for monkeys raised with inanimate surrogates. Differences between rearing groups can only be the result of contrasts in attributes of the substitute mothers.