Tryptophan enhancement/depletion and reactions to failure on a cooperative computer game

Twenty-eight high trait hostility male volunteers played a "cooperative" computer game 4.5 hours after an amino acid drink enhanced with, or depleted of, tryptophan. Each trial involved steering a tank through minefields following directions from an unknown "partner." Failure was experienced when the tank hit a mine or when time ran out. Subjects' moods, verbal aggression, attributions of blame, vocal acoustics, and blood pressure were assessed. Differences between tryptophan groups were not significant for primary measures of anger and verbal aggression. However, depleted subjects reported greater increases in feelings of restlessness and incompetence, were less successful in avoiding mines and showed greater increases in blood pressure during the game. Subjects in both groups sent more negative ratings when they lost the game by virtue of hitting a mine rather than losing by running out of time. However, ratings of the depleted group were less influenced by the reason for losing the game. Also, vocal acoustics showed a group X reason-for-losing interaction in the high-frequency band. Tryptophan-depleted subjects with high scores on Behavioral-Activation-System-Drive were most likely to send negative ratings and those scoring high on Buss-Durkee Hostility Inventory Assault and Guilt to report increased anger after the game.