Open Access

Great apes make anticipatory looks based on long-term memory of single events.

Fumihiro Kano, Satoshi Hirata
DOI: 10.1016/j.cub.2015.08.004
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Seen Once, Never Forgotten

You don't have to be human to like a good horror flick, Kyoto scientists show

Kyoto, Japan -- Having once seen the shower scene in Alfred Hitchcock's 1960 thriller Psycho, who can forget what happens next?

And it turns out that aside from humans, great apes (in this case, chimpanzees and bonobos) also remember events in films -- and can anticipate what takes place in memorable scenes.

Researchers at Kyoto University's Wildlife Research Center, writing in the journal Current Biology, adapted eye-tracking technology for the apes, enabling the team to rec-ord how the apes were viewing various video clips.

"When shown a video for the second time, after a 24-hour delay, the apes clearly an-ticipated what was coming next," explains first-author Fumihiro Kano. "This demon-strates their ability to encode single-experience events into long-term memory."

The team began by creating two series of short films, King Kong Attack and Revenge to King Kong, in which the apes are shown a familiar sort of environment where rather shockingly unfamiliar events take place. For example in the first series, two doors are visible, but an attacking 'King Kong' (in reality, a researcher dressed in a Kong cos-tume) only emerges from the right or left side. 24 hours later, when shown the film again, the apes' attention focused on the side they had seen previously, even before Kong emerged.

Previous studies in this area have been based on prior long-term training of apes.

"What makes our result unique is that the apes encoded the information after only one viewing," says Satoshi Hirata, a senior member of the team. "This ability should help them avoid impending danger, interact socially, and navigate complex environ-ments."

Cannot be unseen
An ape viewer (upper left) intently watches a test film, anticipating that a researcher dressed in an ape costume will emerge from the right-hand door (as indicated by red, eye-tracking dots).


Everyday life poses a continuous challenge for individuals to encode ongoing events, retrieve past events, and predict impending events. Attention and eye movements reflect such online cognitive and memory processes, especially through ‘‘anticipatory looks'' . Previous studies have demonstrated the ability of nonhuman animals to retrieve detailed information about single events that happened in the distant past. However, no study has tested whether nonhuman animals employ online memory processes, in which they encode ongoing movie-like events into long-term storage during single viewing experiences. Here, we developed a novel eye-tracking task to examine great apes' anticipatory looks to the events that they had encountered one time 24 hr earlier. Halfminute movie clips depicted novel and potentially alarming situations to the participant apes (six bono- Q1 bos, six chimpanzees). In the experiment 1 clip, an aggressive ape-like character came out from one of two identical doors. While viewing the same movie again, apes anticipatorily looked at the door where the character would show up. In the experiment 2 clip, the human actor grabbed one of two objects and attacked the character with it. While viewing the same movie again but with object-location switched, apes anticipatorily looked at the object that the human would use, rather than the former location of the object. Our results thus show that great apes, just by watching the events once, encoded particular information (location and content) into long-term memory and later retrieved that information at a particular time in anticipation of the impending events.

Article Information
Kano, F., & Hirata, S.(2015)Great apes make anticipatory looks based on long-term memory of single events. Current Biology , Volume 25, Issue 19, p2513-2517 10.1016/j.cub.2015.08.004