Rewatch the infamous shower scene in Alfred Hitchcock’s thriller, Psycho, and you’ll probably do the same thing everyone else does: look at the shower curtain, waiting for Norman Bates to make his violent entrance. Great apes, scientists have discovered, also make anticipatory eye movements when remembering shocking events. Chimpanzees and bonobos are known for their long-term memories. But usually scientists test them only for their ability to recall where food has been hidden. To find out whether the apes can also remember events they’ve watched, the researchers made two short movies, starring themselves. They showed the films to six chimpanzees and six bonobos, and used eye-tracking technology to record the apes’ eye movements. In one film, a person dressed in an ape suit jumps out from one of two identical doors. In the other, a person grabs a hammerlike object and clobbers the ape character with it (see the video above). The apes watched both films intently. Twenty-four hours later, they were shown the films again, and the scientists again tracked the animals’ eye movements. Just like us watching for that knife in Psycho, the chimps and bonobos looked to the door where they’d previously seen the ape character emerge, the team reports today in Current Biology. They also looked at the hammer in the second film—even though it had been put in a different place this time. The study shows that great apes, like humans, can store and retrieve precise information in their long-term memories, and anticipate impending events, a cognitive skill that likely helps them deal with social intrigue and avoid danger.
(Video credit: Fumihiro Kano, and Kumamoto Sanctuary, Wildlife Research Center, Kyoto University)