Contribution of Recollection and Familiarity Judgements to Rate of Forgetting in Organic Amnesia

The present study sought to determine whether the rate of forgetting in amnesic and control participants varied as the relative contribution of familiarity judgements (or implicit memory) was manipulated. In Experiment 1, rates of forgetting were measured in two recognition conditions in which the relative contribution of familiarity judgements and recollection had been manipulated. No significant group by condition or group by condition by delay effects were found. In Experiment 2, we compared word recognition and word recall tasks on the assumption that this would produce a larger difference in the role of familiarity judgements versus recollection. In this case, we did obtain a significant difference in forgetting rates, the amnesic patients forgetting faster than the healthy subjects in the recall condition. In summary, amnesic patients showed faster forgetting on recall than recognition, which we have attributed to the absence of the opportunity for familiarity judgments in recall testing. We concluded that amnesic patients show a primary deficit in the acquisition of new information (with associated or secondary retrieval deficits), and that, in addition, they show a deficit in long-term retention detectable only on recall (‘high recollection’) testing.