Prior knowledge and age effects in memory: Implications for episodic and short-term/immediate memory
The ageing literature shows robust age-related declines in immediate (e.g. Bopp & Verhaeghen, 2005; Multhaup, Balota & Cowan, 1996; Verhaeghen, 2002; Verhaeghen, Marcoen & Goosens, 1993) and episodic memory (Fleischman, Wilson, Gabrieli, Bienias & Bennett, 2004; Park, 2000; Schaie, 2005; Singer, Lindenberger & Baltes, 2003). However, older adults also consistently show stable or even improving levels of semantic knowledge (Surprenant & Neath, 2007). In younger adults, Hemmer and Steyvers (2009) showed that episodic memory for the properties (i.e. size) of familiar items is influenced by multiple levels of pre-existing knowledge. In this thesis, I developed their paradigm to systematically explore these knowledge effects in healthy ageing for both episodic memory and short-term/ immediate memory. This was done by comparing memory for familiar relative to unfamiliar faces, as well as for the size of familiar everyday objects relative to unfamiliar, random shapes. Across all experiments, both age groups appeared to rely on pre-existing item-based knowledge for the familiar items to the same extent, suggesting no age-related decrement in the use of prior knowledge. Moreover, the result showed that item-specific knowledge for the unfamiliar items develops over the course of the experiment. This became apparent in cases when the distribution of target item sizes was bimodal, as this made session-based learning of the item statistics easier to observe; this experiment-based knowledge/ learning was again equivalent for both age groups. The older adults, however, consistently demonstrated greater reconstruction variability and overall error. I interpreted this as evidence of noisier memory representations of the studied items for the older adults (e.g. Noack, Lovden & Lindenberger, 2014); the findings suggest that this increase in error does not lead to more knowledge-based bias in older adults.
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