Multiple species of distinctiveness in memory? Comparing encoding versus statistical distinctiveness on recognition.

The distinctiveness effect refers to the memorial benefit of processing unique or item-specific features of a memory set relative to a non-distinctive control. Traditional distinctiveness effects are accounted for based on qualitative differences in how distinctive items are encoded and subsequently retrieved. This study evaluates whether a separate species of distinctiveness - statistical distinctiveness - may provide an additional benefit to memory beyond traditional task-based processes. Statistical distinctiveness refers to the relative frequency with which a specific memory item or set is processed. The current study examined the presence of statistical distinctiveness through a series of levels-of-processing mixed groups in which related lists were studied using two of the following three tasks to promote either shallow ("E" identification), neutral (reading silently), or deep/distinctive (pleasantness ratings) processing followed by a recognition test. Participants studied lists in which these tasks were used frequently (80% of lists), equally (50% of lists), or infrequently (20% of lists). No recognition advantage was found when tasks were completed infrequently versus frequently. Instead, recognition was greatest for the deeper/more distinctive task - a pattern consistent with an encoding but not a statistical distinctiveness account.