Fallacious Reversal of Event-Order During Recall Reveals Memory Reconstruction in Rhesus Monkeys

One of the key features of episodic memory is its lability but whether nonhuman primate species can construct, still less reconstruct, representations of their past remains controversial. Akin to false memories seen in humans, here we show that rhesus macaques are capable of “remaking” or reconstructing memory traces of dynamic, naturalistic video content. First, the monkeys’ temporal order judgement performance increases over repeated viewing of the same videos across days, suggesting they possess long-term memory capacity of hundreds of videos. However, following encoding videos that were displayed in a reverse, out-of-ordinary sequence, monkeys automatically reconstructed details which violate physical normality and assimilated them into long-term memory in accordance to their general understanding of the statistical structure of the environment. This effect in turn produces systematic reversal errors in their subsequent order judgment of events and can be sustained over 1 month. Moreover, this putative memory distortion effect due to incongruence with their priors is significantly accentuated by ecological relevance of the videos. Demonstrating in macaque monkeys a unique form of mnemonic malleability to one’s prior knowledge carries implications for the emergency of memory retrospection in the primates.