If you’ve ever watched Silence of the Lambs, you know there’s a particularly creepy moment in a dark basement: A killer’s hand reaches out toward Jodie Foster, and you’re not sure if she’ll live or die. Once you’ve seen the movie, you’ll inevitably anticipate that scene with terror on subsequent viewings.
Turns out, bonobos and chimpanzees do the same, according to a study out today in Current Biology.
As two of our genetically closest relatives, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) have a lot in common with humans, including excellent long-term memories. Less clear, however, is how these great apes encode those memories. Humans record all sorts of details and learn to anticipate certain sequences of events, whether that’s everyday affairs or the final moments of a thriller. Could bonobos and chimpanzees do the same, or are their memories limited to simpler tasks, such as finding food?
Just as humans do, apes seemed to anticipate crucial events.
Biologists Fumihiro Kano and Satoshi Hirata tackled that question in the obvious way: They made two short movies, each in two versions, and showed them to six bonobos and six chimpanzees at Kyoto University’s Kumamoto Sanctuary. In one movie, King Kong Attack, an assistant in an ape costume emerges from one of two doors and steals a nearby researcher’s banana. In the second, Revenge to King Kong, King Kong attacks a researcher, who retaliates using either a hammer or a sword. Each ape watched one of the movies on one day and watched the same one again 24 hours later.
During each screening, Kano and Hirata used an eye-tracking camera to determine what the apes were paying attention to at each moment. They then tallied up how much time each ape spent looking at the target objects—which door Kong uses in King Kong Attack, or the weapon the aggrieved researcher selects in Revenge on King Kong—and computed the difference between the first and second viewings.
Just as humans do, the apes seemed to anticipate crucial events. They spent more time looking at the target objects in the second screening than in the first, Kano and Hirata found, and also started looking toward those targets earlier during the second screening compared with the first. Some even stopped snacking and drinking juice during tense moments. That, the researchers argue, indicates that apes were anticipating coming events, as opposed to reacting, even though they had only watched the movies once.
Such talents “should help animals to avoid impending dangers, enhance social learning, and navigate competitive/cooperative social environments,” Kano and Hirata write. And, because apes are known to communicate information about locations and objects by following each others’ gaze, “apes’ memory-based anticipatory looks may also help a group … store shared memories.”
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