How does counterfactual imagination affect our ability to remember the past? EEG and behavioural evidence

Vivid imagination is a known source of false memories. However, often when we imagine the past we do not create new memories but instead we imagine counterfactual versions of past events and consider how our memories could have been different. Flexible and reconstructive episodic memory processes have many adaptive purposes; however, they are also known to leave the original memory susceptible to modification and updating. Previous studies have shown that counterfactual reimagined versions of the past can be mistaken for memories of real events but only a limited number of studies have considered how counterfactual imagination may affect our ability to remember the veridical version of what really happened. This research question was therefore the focus of the current thesis. In an initial series of behavioural experiments, I investigated how counterfactual imagination could induce memory errors in the context of eyewitness testimony. In subsequent experiments with combined EEG and behavioural measures, I considered more commonplace memory decisions in our everyday life; when we attempt to remember if we performed simple actions, such as whether we locked our front door or only imagined this action. The findings across these experiments indicate that counterfactual imagination could either strengthen or impair our memory of the past depending on different contextual factors. I also used EEG to investigate the neurocognitive mechanisms that are engaged when we make these kinds of decisions during memory retrieval. Analysis of both ERPs and oscillatory EEG power showed separable effects related to the reactivation of the memory and subsequent post-retrieval processes. Lastly, I conducted representational similarity analysis on the EEG data to further explore the processes engaged when recalling a memory associated with an imagined counterfactual. Taken together, the research in this thesis provides a behavioural and neurocognitive explanation for how counterfactual imagination affects our ability to remember the past.