Effects of acquired brain injury on adaptive choice and the role of reduced sensitivity to contingencies

The present investigation examined the proposal that brain injury reduces sensitivity to consequences. On a laboratory task, controls and subjects with brain injury made repeated choices between a small amount of money and a larger amount of money followed by a post-reinforcer delay of 3, 12, 18, or 24 seconds. Increasiong delays lowered reinforcement densities (i.e. money available per minute) associated with large reinforcers. Consequently, choosing large reinforcers became less adaptive. Results showed subjects with brain injury made less adaptive choices and earned significantly less money than controls, because of a preference for large reinforcers with low reinforcement densities. Maladaptive choice was not attributable to deficits in discriminating reinforcer magnitudes or delays. Results suggest individuals with brain injury may remain sensitive to consequences but fail to discriminate among significant response-consequence relations (i.e. contingencies). This view, emphasizing basic learning processes, may account for some problems in skill acquisition and adaptive choice.