Inhibitory Control as a Mediator of Individual Differences in Rates of False Memories in Children and Adults
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philospy
The primary aim of this dissertation is to address an important issue of individual susceptibility to false memories. Specifically, what is the role inhibitory control (IC) in children’s and adult’s propensity to producing false memories? Inhibitory control within the context of the current study is defined on the basis of performance on selective attention tasks. Inhibitory control is discussed within this dissertation as it is reflected in two selective attention tasks, Stroop and Negative Priming. While the false memory effect, as reflected in the Deese/Roediger and McDermott paradigm (Roediger & McDermott, 1995), is one of the most widely studied memory phenomenon, the current study is important as it provides some insights into the relation between attention and memory. An interesting finding in the DRM false memory effect is that participants often report having a clear false memory of having seen or heard the non-presented critical lure item (CL item). Such memory illusions have been informative on how memory works. The current study adds to this body of research by providing converging evidence of how individual differences in the sensitivity to the false memory effect may occur, and how this sensitivity may reflect the same IC mechanisms involved in selective attention tasks. The basic notion examined within this dissertation is that when recognition memory is tested in the DRM paradigm, individuals have to select information that was studied and simultaneously inhibit highly activated yet non-presented information in memory, in order to correctly reject the CL item. If the notion that individual differences in sensitivity to the false memory effect is indeed related to a basic IC mechanism, then a relationship should be found between measures of IC in selective attention tasks and rates of false memories in the DRM test. The current study incorporates three experiments. Experiments 1 and 2 are broken down into parts ‘a’ and ‘b’, with each part varying in respect to the IC measure. In part a, participants were assigned to an inhibitory control group (IC group) on the basis of Stroop interference. In part b, participants are assigned to IC groups on the basis of a combined measure of inhibitory control that is, Stroop and Negative Priming. The third experiment assigned participants on the basis of a combined measure of IC, and then considered the relation between the duration of IC over a number of DRM word-lists presented simultaneously prior to the recognition test. Experiment 3 also compared the robust effect of IC on the propensity to produce false memories across all three experiments. The results of this study can be summarized as follows. In each experiment there was clear evidence of a relation between IC estimates and proportion of false memories. As predicted, individuals assigned to a Less IC group produced a higher proportion of false memories than those assigned to the More IC group. Inhibitory control differences did not modulate differences in correct or incorrect recognition in general (hits and false alarms to unrelated distractors). This second finding is important because it suggests a specific effect of IC in false memories, rather than a general breakdown in memory processes. The IC effect in false memories occurred in children (8-year olds and 10-year olds) as well as adults. Furthermore, the IC effect appeared to be additive with age; i.e., all groups produced a similar pattern across all three experiments. Last, the combined estimate of IC was found to be a more sensitive measure of false memories than a single index of IC; however, this was found in relation to adults but not for children. A number of additional manipulations and measures of interest were also included. Experiment 2 found clear evidence of an effect of IC on remember responses, not only were Less IC individuals more likely to produce false alarms to critical lure items, they were also more likely to distinctly respond they “remembered” the CL item as opposed to only “knowing” the CL had been presented. Examination of reaction times (RTs) to false alarms as a function of IC group found the Less IC group were faster to make false alarm responses to CL items, whereas the More IC group were slower to make false responses CL items. As predicted the relation between IC and the false memory effect was modulated by the random versus blocked presentation manipulation in Experiment 3. Specifically, decreased rates of false memories were found in the random presentation format compared to the blocked format. Interestingly however, a small effect of IC group in false memories was found even in the random condition. From this study it can be concluded that individual susceptibility to the false memory effect is in part modulated by inhibitory control. Individuals who demonstrate less effective IC show a greater propensity to false memories than those who demonstrate more effective IC. The IC effect of false memories was found to be robust, with converging evidence found across all three experiments. In relation to the development of inhibitory control, consistent with the research of Pritchard and Neumann (2004, 2009), and Lechuga and colleagues (2006), the results of this study suggest IC is fully developed in young children. However, their ability to accurately encode, retain and retrieve information would appear to develop at a different rate than IC. Specifically, it may be that while younger children are able to utilize IC in memory processes, they have yet to fully develop a richly interconnected semantic network. On the other hand, older children and adults would appear to have a more fully developed semantic network. This series of experiments presents a novel demonstration of the relation between inhibitory control and false memories. As such, this study has the potential to provide new insight into a cognitive mechanism that may be responsible for both developmental trends and for individual differences in the regulation of false memories. Moreover, if the mechanism responsible for mediating false memories is causally linked to performance on selective attention tasks in the systematic way that is proposed, it may be possible in the future to utilize IC measures to assist in identifying individuals who have an exaggerated propensity to form false memories, as well as those more prone to resist them.