Distinctiveness enhances long‐term event memory in non‐human primates, irrespective of reinforcement

Abstract

Non-human primates are capable of recalling events that occurred as long as three years ago, and are able to distinguish between similar events; akin to human memory. In humans, distinctiveness enhances memory for events, however, it is unknown whether the same occurs in non-human primates. As such, we tested three great ape species on their ability to remember an event that varied in distinctiveness. Across three experiments, apes witnessed a baiting event in which one of three identical containers was baited with food. After a delay of two weeks, we tested their memory for the location of the baited container. Apes failed to recall the baited container when the event was un-distinctive (Experiment 1), but were successful when it was distinctive (Experiment 2), although performance was equally good in a less-distinctive condition. A third experiment (Experiment 3) confirmed that distinctiveness, independent of reinforcement, was a consistent predictor of performance.These findings suggest that distinctiveness may enhance memory for events in non-human primates in the same way as in humans, and provides further evidence of basic similarities between the ways apes and humans remember past events.

Non-goal-directed recall of specific events in apes after long delays

“…This could potentially explain why the addition of a social cue did not improve recall performance. As such, our results suggest that using experimenter identity as a social cue may be of limited effect at retrieval, especially in the presence of other more unique and diagnostic cues, something that is consistent with other work ( [49], MJ Beran 2016, personal communication).…”

Time-space–displaced responses in the orangutan vocal system

“…Third, the low probability and high unpredictability of encountering mid- to large-sized felid predators, which live at low densities in large ranges, are likely to make an encounter and its corresponding response by the mother an unusual event. Considering that unusual and emotionally laden events are more memorable than usual and neutral events, it is conceivable that orangutan youngsters could make this association ( 35 , 36 ). Fourth, a growing body of evidence for episodic-like and event memory in nonhuman primates ( 37 ) and human infants [who, at the age of 17 months, remember temporally ordered sequences of events and actions after a delay period of 6 weeks ( 38 )] suggests that displaced reference might enable learning in young orangutans.…”

Long-Term Memory of Past Events in Great Apes

“…Examining distinctiveness (Hunt & Worthen, 2006;Hunt & Smith, 1996), Lewis, Call, and Berntsen (2017a) demonstrated that apes can remember a distinctive event when probed by features that overlap with the distinctive event ( Figure 1, Cue environment 3). Apes remembered which container food had previously been hidden under when presented with cues that occurred during the hiding event, but only when the event was distinctive.…”

“…As there were three containers, chance was 33%. (*p<0.05) (Adapted fromLewis et al, 2017a). is the author's version of a work that was accepted for publication in Current Directions in Psychological Science.…”