Relations between decision-making deficits and discriminating contingencies following brain injury

Deficits in decision-making characterized by failures to respond adaptively to consequences that follow responding are common following brain injury. To examine decision-making about consequences, individuals with and without acquired brain injury responded under different response-reinforcer contin gencies. In two control conditions, reinforcement was contingent on respond ing and response repetition. Results showed responding (pressing four compu ter keys) by both groups produced similar amounts of reinforcement (money) and highlight equal sensitivity to money as a reinforcer. In subsequent exp erimental conditions, reinforcement was contingent upon varying responses. Results showed both groups produced variable response patterns, but injured subjects earned less reinforcement than controls. With instructions to var y responding across trials, injured subjects earned similar amounts of rein forcement as controls. Collectively, the results suggest reductions in sens itivity to contingencies may be present following injury and function as on e behavioural mechanism of maladaptive decision-making.