Additional variables factors

We explored the impact of numerous additional variables. The effect of each individual familiarity rating for each vegetable was examined using a 2 (group; younger vs. older) x 2 (relative size; smaller vs. larger) ANCOVA for absolute error, though familiarity was a non-significant covariate; F(1, 56) = 3.3, p = .074. Moreover, we examined the level of interference during the delay task (the number of mathematical sums completed). An independent samples t-test indicated that younger adults (m = 7.64, SD = 3.5) completed more sums on average than the older adults (m = 4.62, SD = 1.62) [t(56) = 4.29, p < .001], which was found to be a significant covariate. When running an ANOVA for just group by error, there was a highly significant group difference; F(1, 56) = 35.53, p < .001. When delay was added as a covariate, although group remained significant, the F-value drastically decreased – F(1, 56) = 13.38, p < .001 and delay remained significant, F(1, 56) = 11.05, p < .001, indicating that the level of decay induced by the delayed task had a significant effect upon error. Moreover, once

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the level of delay was accounted for, the group differences declined, suggesting that the delay had a significant impact on the older adults’ responses.

Furthermore, an independent t-test confirmed a significant group difference for the Picture Sequence Memory Test of episodic functioning; t(57) = 5.8 p < .001, with younger participants (m = 22.62, SD = 7.58) scoring higher than older (m = 10.86, SD = 10.86). Moreover, when analysing group differences in terms of absolute error, there was a significant group difference, F(1, 56) = 8.56, p < .001. However, when episodic visual memory capacity was added as a covariate, the group difference was no longer significant; F(1, 56) = 1.22, p = .274 and episodic functioning was marginally significant, F(1, 56) = 4.3, p = .044, thus indicating a potential causal explanation for the observed group differences. In terms of semantic capacity, there was also a significant group difference, with younger adults scoring lower (m = 11.51, SD = 2.16) than older (m = 15.45, SD = 3.36) [t(49) = -5.0, p < .001]. However, when run as a covariate against absolute error, it was found to be non-significant.

Lastly, the participants’ responses were analysed to assess whether their responses were influenced by the size of the item shown at test by running a regression per participant determining whether test size was a significant predictor of participants’ responses. Test size was a non-significant predictor for all participants bar three (one younger and two older), suggesting that test position had little systematic effect upon responses. These three participants possibly used the test position as an ‘anchor’ to influence their reconstruction response, but removing the participants made no overall difference to the model.

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4.2.3 Discussion

The data for this study suggest that 1) older adults show more absolute error in their responses and 2) older and younger adults use prior knowledge to the same extent. We found that although prior knowledge led to more accurate reconstructions, with participants demonstrating less error for the familiar items than the unfamiliar items, accuracy declined with age. The older adults also demonstrated more variation in the responses (indicated by larger SD’s for their responses), which we propose is indicative of noisier memory representations. The results thus showed that older adults made larger (and more varied) reconstruction errors despite both groups using object-level and superordinate category-level knowledge to the same degree. This suggests that greater memory error is not compensated for by a greater reliance on prior knowledge. The analyses suggest that the greater level of error for the older adults may have been affected by the delay, potentially due to greater interference between encoding and retrieval. Moreover, once episodic visual memory functioning was accounted for, the group difference was no longer significant, suggesting that this could have also been a causal factor in the observed level of error. To draw any substantial conclusions for our understanding of the mechanisms involving age differences, however, these factors would need further investigation.

The findings also suggest that both age groups learned categorical consistencies for the unfamiliar stimuli. This was demonstrated through the observed intercept difference for the unfamiliar items. This difference is typically attributed to object-level knowledge. It was thus surprising that in the current study, participants appeared to learn the underlying category structure of the presented items (the items tested in the current task were presented either smaller than the normative mean or larger) despite

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little knowledge of the items. It thus appears that this bi-modal presentation of the items caused participants to learn the two distinct categories.

Overall, therefore, our data suggests that older adults rely on prior knowledge to the same extent as younger adults, despite showing greater error. However, due to the surprising use of item-based knowledge for the unfamiliar items, we want to test our hypothesis for the effects of learning on memory reconstruction. Moreover, we wished to establish if the pattern of findings reported above was replicable (with a slightly different task). We aimed to determine whether the effects observed here still hold when we present items using a distribution approximating normal (i.e. most items presented at a value close to their respective normative means, rather than more extreme sizes) instead of a bi-modal distribution. We predict that in the absence of two distinct underlying categories (items smaller or larger than the mean), participants will show no effect of learning for the unfamiliar items. To test this, we designed a continuous recognition task which was much similar to Hemmer and Steyvers’ (2009) original paradigm.