Keeping track of time: evidence for episodic-like memory in great apes

Abstract

Episodic memory, as defined by Tulving, can be described in terms of behavioural elements (what, where and when information) but it is also accompained by an awareness of one’s past (chronesthesia) and a subjective conscious experience (autonoetic awareness). Recent experiments have shown that corvids and rodents recall the where, what and when of an event. This capability has been called episodic-like memory because it only fulfils the behavioural criteria for episodic memory. We tested seven chimpanzees, three orangutans and two bonobos of various ages by adapting two paradigms, originally developed by Clayton and colleagues to test scrub jays. In Experiment 1, subjects were fed preferred but perishable food (frozen juice) and less preferred but non-perishable food (grape). After the food items were hidden, subjects could choose one of them either after 5 min or 1 h. The frozen juice was still available after 5 min but melted after 1 h and became unobtainable. Apes chose the frozen juice significantly more after 5 min and the grape after 1 h. In Experiment 2, subjects faced two baiting events happening at different times, yet they formed an integrated memory for the location and time of the baiting event for particular food items. We also included a memory task that required no temporal encoding. Our results showed that apes remember in an integrated fashion what, where and when (i.e., how long ago) an event happened; that is, apes distinguished between different events in which the same food items were hidden in different places at different times. The temporal control of their choices was not dependent on the familiarity of the platforms where the food was hidden. Chimpanzees’ and bonobos’ performance in the temporal encoding task was age-dependent, following an inverted U-shaped distribution. The age had no effect on the performance of the subjects in the task that required no temporal encoding.

Comparative Developmental Psychology: How is Human Cognitive Development Unique?

“…The field of comparative psychology, in contrast, investigates the evolutionary origins of human cognition via research with humans' closest living relatives, non-human primates, as well as other species of evolutionary interest. This field has shown that many primate species exhibit an array of complex abilities previously thought to be unique to humans, including reasoning about others' perceptions and knowledge, episodic memory and planning, and the ability to use and create complex tools Flombaum and Santos, 2005;Humle and Matsuzawa, 2002;Martin-Ordas, Haun, Colmenares, and Call, 2009;Mulcahy and Call, 2006;Seed and Byrne, 2010) Both developmental and comparative approaches have therefore been critical in generating and testing hypotheses regarding the origins of human-unique cognition. Yet little attention has been paid to the intersection of developmental and comparative inquiry: studies of cognitive development across species.…”

The evolution of episodic memory

“…Here, we examine the three main approaches used to study the memory for events in context: ( (16)]. This approach has also been adapted to many mammalian species, including rats (14,(17)(18)(19), mice (20), meadow voles (21), pigs (22), nonhuman primates (23,24), and humans (25,26). It is important to note that the structure and flexibility criteria have been much less investigated than the content criterion so it remains to be determined whether all these species will meet all three behavioral criteria.…”

Memory processing in great apes: the effect of time and sleep

“…A study using the same procedure as the one reported here showed that apes did remember the location of a reward after 1 or 2 h RIs [23]. However, unlike the subjects tested here, those subjects remained in the testing room during the RI, which may have minimized interference by other activities in making memories temporarily inaccessible [9,24].…”