Personality in monkeys: Factor analyses of rhesus social behaviour

Three factor analyses were performed on social interaction data from 168 juvenile macaques. Animals were tested in stable quadrad peer groups; in newly-formed dyads with infant, juvenile, and adult stimulus monkeys; and in similar triads with the stimulus animal plus a familiar cage-mate. Factors emerged, most strongly in the most stable condition, which were interpreted as affiliative, hostile and fearful. These factors were almost entirely independent and resembled the extraversion, psychoticism, and emotionality factors frequently found in humans.