Overall Performance

Participants had a mean overall accuracy of 0.82 (SD = 0.10), with a mean adjusted hit rate (H’) of 0.71 (SD = 0.19) and a mean adjusted correct rejection rate (CR’) of 0.92 (SD = 0.08). Participants overall sensitivity was significantly above chance (d'; M = 2.28, SD = 0.89), as confirmed by a single-sample t-test, t(29) = 14.20, p < 0.001, d =

2.593. Overall, participants has a conservative bias (c; M = 0.49, SD = 0.37), as confirmed by a single-sample t-test, t(29) = 7.29, p < 0.001, d = 1.331.

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3.7.2 Analyses of Hit and Correct rejection rates

Firstly, to investigate how the mnemonic status of concurrent items affected

recognition judgements of old and new items, participants’ H' and CR' rates for items presented alone, paired with a New or paired with a High Familiarity item were examined (Figure 3.10).

Figure 3.10: Decision accuracy for a) targets and b) lures presented alone or paired with concurrent items of differing mnemonic statuses.Bars show mean proportion of targets (blue) and lures (green) correctly identified when these were presented alone or paired with concurrent items of varying mnemonic statuses. Error bars represent the standard error.

H' rates were not affected by the mnemonic status of the concurrent item (O, M = 0.73, SD = 0.18; N, M = 0.70, SD = 0.21; HF, M = 0.71, SD = 0.18), as confirmed by a one-way repeated measures ANOVA with the mnemonic status of the concurrent item (O, N, HF) as the within-participant factor, F(2, 58) = 0.699, p = 0.501, 9:; = 0.024. Contrastingly, the mnemonic status of the concurrent item differentially affected CR' rates, as also demonstrated by a one-way repeated measures ANOVA with the mnemonic status of the concurrent item (O, N, HF) as the within-participant factor,

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F(2, 58) = 6.05, p = 0.004, 9:; = 0.173. Bonferroni corrected pairwise comparisons showed that participants had higher CR' rates for lures paired with a High Familiarity item (M = 0.93, SD = 0.08) than when the lures were presented alone (M = 0.89, SD = 0.10), p = 0.002. However, no differences were seen between CR' for lures presented with a New item and those presented either alone or with a High Familiarity item, p = 0.0479, and p = 0.229, respectively.

3.7.3 Analyses of sensitivity (d') and bias (c)

Participants’ bias (c) and sensitivity (d') - the combined effect of H' and CR' – were also investigated. To question how the mnemonic status of concurrent items affected d' and c, the data were collapsed for each participant across conditions based on the mnemonic status of the concurrent items as follows (mnemonic status of questioned item is underlined):

N-N and HF-N = concurrent N

N-HF and HF-HF = concurrent HF

N and HF = None (O)

Mean d' and c for items presented alone, paired with New, and paired with High Familiarity concurrent items are presented in Figure 3.11. The mnemonic status of the concurrent item did not affected participants d' as demonstrated by a one-way repeated measures ANOVA with the mnemonic status of the concurrent item (O, M = 2.03, SD = 0.87; N, M = 2.10, SD = 0.90; HF, M = 2.30, SD = 0.81) as the within- participant factor, F(2, 58) = 2.44, p = 0.096, 9:; = 0.078.

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Figure 3.11: (a) Sensitivity and (b) Bias for items presented alone and paired with concurrent items of differing mnemonic statuses. Bars show mean parameter estimates of (a) sensitivity (d') and (b) bias (c) under

conditions where recognition is tested while concurrently presenting no item (None), a New item or a High Familiarity item. Error bars represent standard errors.

As illustrated in Figure 3.11b, the presence of a concurrent item, and its mnemonic status appeared to influence participants’ c. A one-way repeated measures ANOVA, F(2, 58) = 5.71, p = 0.005, 9:; = 0.165, and corresponding Pairwise comparisons

revealed that participants’ were significantly more conservative for items paired with a High Familiarity concurrent item (M = 0.51, SD = 0.35), compared to when items were presented alone (M = 0.31, SD = 0.35), p = 0.005. However, there were no statistical differences in participants’ c between items presented with a New concurrent item (M = 0.40, SD = 0.43) and either an item presented alone or with a High Familiarity item, p = 0.350, and p = 0.290, respectively.

Although no differences in d' were observed, for consistency, relative c (c') as scaled by d' for the differing conditions was also examined (see Section 2.2.4, page 46). This was calculated in an identical manner to that in Experiment 2. Similarly to

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for items presented alone. As such, c' was examined for a subset of 29 individuals, 86.2% females (n = 25) and 13.8% males (n = 4; mean age = 20.76, rage = 18-28 years). Mean c' for items presented alone, paired with a New or paired with a High Familiarity concurrent item are presented in Figure 3.12.

Figure 3.12: Bias for items presented alone or paired with concurrent items of differing mnemonic statuses. Bars show mean parameter estimates of bias (c) relative to sensitivity (d') under conditions where recognition is tested while concurrently presenting no item, a New item or a High Familiarity item. Error bars represent standard errors.

Although participants appear to have a more conservative c' for items paired with a concurrent item than for items presented alone, a one-way repeated ANOVA showed no significant difference in c' across the different conditions, F(2, 56) = 2.008,

p = 0.144, 9_:; _{= 0.067. This differs from the differences in absolute c outlined} previously.

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3.8

Discussion

The aim of this experiment was to validate the findings from Experiment 2 under conditions of improved recognition memory performance. Participants did

demonstrate better recognition for Digimon and Pokémon characters than fractals, however, dissimilarly to Experiment 2, the mnemonic status of concurrently

presented items did not affect the correct identification of either old or new items. This reflected the absence of an effect of the mnemonic status of concurrent items on both memory sensitivity and bias. As such, the results obtained in Experiment 2 are not replicated under conditions of improved recognition memory.

The combined presence and mnemonic status of a concurrent item did however have differing effects on the correct identification of old and new items. The inclusion of a single item condition revealed that the old item recognition was unaffected by the presence of a concurrent item, while correct identification of a new item was aided when this was paired with a highly familiar item compared to when it was presented alone. However, presentation of a concurrent novel item had no effect on the correct identification of lures compared to when these were

presented alone. The differences in the disruption occurred in the absence of an enhanced memory sensitivity for items presented with highly familiar concurrent items compared to those presented alone, but reflect a shift in bias. Indeed, participants are relatively more conservative (more inclined to endorse “old” decisions) under conditions when concurrent items are highly familiar than when these are presented alone, resulting in the observed higher correct rejection rate. Similarly to Experiment 2, it appears the combined presence and mnemonic status of a concurrent item drive participants to amend their criterion on an item-by-item basis. Similarly to Experiment 2, the interference observed occurred despite the delayed presentation of concurrent items onscreen compared to target items. This suggests that processing of novelty and familiarity is differentially disrupted by a concurrent item presented within a relatively short time frame (<1 second), despite these not being presented simultaneously.

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