Ageing and secondary-distinctiveness-based effects: the orthographic distinctiveness effect is more robust than the bizarreness effect.

Differences related to ageing were investigated in two cases of secondary-distinctiveness-based effects: the bizarreness effect and the orthographic distinctiveness effect. A secondary distinctiveness effect means that items that are unusual compared to one's general knowledge stored in permanent memory are better remembered than common items. Experiment 1 confirmed that ageing diminishes the facilitative effects of bizarreness in a mixed list design with equal numbers of bizarre and common images. We suggest that the impaired bizarreness effect in older adults (above age 70) may be due to reduced attentional resources, since no bizarreness effect was observed for younger adults in the divided attention condition. Experiment 2 studied the orthographic distinctiveness effect in ageing for the first time. Contrary to our expectations, an orthographic distinctiveness effect was observed for all participants including older adults and younger adults in a divided attention condition. Because reduced attentional resources due to normal ageing or to experimental manipulation did not impact the facilitative effects of orthographic distinctiveness, our findings suggest that the orthographic distinctiveness effect may be mediated by more automatic processing.