Event memory and misinformation effects in a gorilla (Gorilla gorilla gorilla)


Event memory and misinformation effects were examined in an adult male gorilla (Gorilla gorilla gorilla). The gorilla witnessed a series of unique events, involving a familiar person engaging in a novel behavior (experiment 1), a novel person engaging in a novel behavior (experiment 2), or the presentation of a novel object (experiment 3). Following a 5- to 10-min retention interval, a tester gave the gorilla three photographs mounted on wooden cards: a photograph depicting the correct person or object and two distractor photographs drawn from the same class. The gorilla responded by returning a photograph. If correct, he was reinforced with food. Across three experiments, the gorilla performed significantly above chance at recognizing the target photograph. In experiment 4, the gorilla showed at-chance performance when the event was followed by misinformation (a class-consistent, but incorrect photograph), but significantly above-chance performance when no misinformation occurred (either correct photograph or no photograph). Although the familiarity can account for these data, they are also consistent with an episodic-memory interpretation.

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    This was surprising because a familiar target was always present, so the testers could have been above chance by always ruling out the familiar target. Tester B.L.S. used this strategy, but tester T.C. never adopted this particular strategy. Based on his incorrect responses, King did not use this strategy either.


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The research was partially funded by the Grants-in-Aid program from the Florida International University College of Arts and Sciences. Monkey Jungle and the DuMond Conservancy provided logistical support for the project. We are grateful to Monkey Jungle for access to King and for employees’ time. The authors thank Jeannice Blazquez for testing King, and Robert Castillo for constructing stimuli. We thank Sharon Du Mond and Steve Jacques of Monkey Jungle for their encouragement, cooperation, and assistance. We thank Tina Casquarelli, Yuri Mitzkewich, and Julie Kerr of Monkey Jungle for their time and expertise.

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Correspondence to Bennett L. Schwartz.

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Schwartz, B.L., Meissner, C.A., Hoffman, M. et al. Event memory and misinformation effects in a gorilla (Gorilla gorilla gorilla). Anim Cogn 7, 93–100 (2004).

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  • Primates
  • Gorillas
  • Memory
  • Episodic memory
  • Misinformation effects