Visual observing by rhesus monkeys: influence of potentially threatening stimuli

7 rhesus monkeys were afforded the opportunity to observe a series of projected color slides of other monkeys exhibiting five content categories of social-communicative behavior (submission, intense threat, mild threat, grooming, and neutral behavior) combined with two levels of familiarity (familiar vs unfamiliar) with reference to the animals depicted in the slides. Mean duration of observing was significantly influenced by the social-communicative content categories, while mean frequency of observing was significantly affected by the familiarity dimension. The data were discussed in terms of the threat potential or fear-arousing capacity of social stimuli in relation to visual obsrving.