Out-of-body experience favors emotional memory consolidation

Body ownership reflects our ability to recognise our body at a certain location, enabling us to interact with the world. Emotion has a strong impact on memory and body ownership; interestingly, skin temperature may at least in part mediate this impact. Previous studies have found that out-of-body experiences (OBE) impair memory encoding and cause skin temperature to drop. In the present study a new method for inducing OBE was designed and their impact on a different stage and type of memory processing (emotional memory consolidation) and on skin temperature was investigated. In our experiment, we presented three types of emotional pictures (neutral, pleasant, unpleasant) before inducing OBE and testing our participants’ recognition memory in a retrieval session. Throughout the whole experiment, both neck and hand skin temperature were measured using iButtons. Participants’ performance was calculated using d-prime and statistical analyses included one-way ANOVA, probing the relationship between the score on the OBE questionnaire, performance and skin temperature; we also compared the differences between the experimental and a control group. Results showed that OBE favour emotional memory consolidation and cause a temperature increase, supporting the embodied cognition theory as proposed by Anderson (2003). Future studies should expand our findings, to rule out that participants experiencing OBE could have a better memory at baseline or that temperature could be increased due to other reasons.

On the relationship between the rate of learning and retrieval-induced forgetting

A plethora of studies demonstrated that repeated selective retrieval of target items from semantic categories has an adverse memory effect on semantically-related memories, a phenomenon called retrieval-induced forgetting (RIF). However, there is a range of boundary conditions for RIF. For instance, forming interconnections between target and competitors, long-term delay without sleep between practice and final recall, and the form of learning all attenuate the effect of selective practice on the accessibility of semantically-related competitors. The aim of the present research was to investigate the latent general preconditions behind the reductions of RIF. In Experiment 1 participants learned category-exemplar pairs with repeated study or combined study-full test sessions followed by a selective retrieval practice and a full cued-recall test. We found lower difference between performance on the non-practiced items from practiced categories (Rp-) and their baseline from unpracticed categories (Nrp-) suggesting a reduction in retrieval-induced forgetting. However, regression analysis revealed that this was possibly caused by the increased recall performance independently from the presence of an initial full retrieval session. Therefore, in Experiment 2 participants learned the same pairs through a study followed by two study, two test or combined study-test cycles. As the consequence of increased rate of learning we confirmed the complete absence of retrieval-induced forgetting with Bayes factor analysis. Our results suggest that the adverse memory effect of selective retrieval practice shows a non monotonic dependency on the strength of the mnemonic representations.