Drug effects upon choice behavior in mixed motive games

It was hypothesized that strategic choice behavior is sensitive to changes in utility or affectively toned expectancies resulting from ingestion of mood-active drugs. A series of symmetrical two-person, mixed motive games was constructed upon the four non-trivial archetypes defined by Rapoport (1967). To heighten conflict, these were played for substantial amounts of real money. D-amphetamine, amobarbital, and a mixture of the two were selected as treatments likely to produce significant affective changes, and hence by hypothesis to alter volitional outcome. Both of the amphetamine conditions produced the expected changes in mood self-ratings. They also significantly influenced several dimensions of choice behavior, thus establishing that the latter are sensitive to mood-active agents. However, the directions of change in choice behavior were not predictable from the directions of mood change, and some could better have been oppositely predicted.