d-Amphetamine induced changes in social interaction patterns.

The behavioral effects of d-amphetamine were studied in a group of stumptail macaques in a large outdoor enclosure. d-Amphetamine altered characteristic patterns of aggressive and affiliative behaviors in adult males that received the drug. Each monkey that received d-amphetamine increased its aggression toward non-adult animals in the group and decreased aggression toward adult members. In subjects for which genealogy was known, d-amphetamine increased aggression toward kin-related members of the group and decreased aggression toward non-kin monkeys. The effects of the drug on affiliative behaviors were less uniform and, therefore, less conclusive. Three subjects decreased affiliation and two increased affiliation toward non-adult monkeys. The results demonstrate that d-amphetamine can alter substantially the behavior of drug-treated members of a group and, in addition, that the drug can indirectly affect specific subsets of the group even though they did not receive the drug.