Processing efficiency and directed forgetting in bipolar disorder.

We hypothesized that patients with bipolar disorder would demonstrate verbal recognition performance deficits consistent with processing efficiency theory, a theory about how emotional states modulate performance by interfering with working memory resources or increasing cognitive arousal/effort. We predicted that (1) a manic group (n=26) would demonstrate slow reaction time (RT) and low accuracy, (2) a euthymic group (n=23) would demonstrate slow RT to maintain high accuracy; and (3) a healthy comparison group (n=25) would demonstrate fast RT and high accuracy. The groups were administered symptom-rating scales and compared on a computerized, trial-by-trial, directed forgetting in recognition task. This task requires participants to comply with an overt instruction to forget irrelevant studied words, and it places a relatively high demand on working memory. The manic group was impaired on directed-forgetting sensitivity; however, when RT was statistically controlled, the groups demonstrated similar directed-forgetting effects. These findings are consistent with processing efficiency theory. They suggest that bipolar patients perform directed forgetting in recognition by increasing effortful control at encoding at the expense of processing efficiency, although acute mania reduces the capacity for control, thereby impairing recognition performance. Problems with processing efficiency are viewed as trait characteristics of bipolar disorder that may be overlooked by traditional error-based assessments.