Assessing Distinctiveness Effects and “false Memories” in Chimpanzees (pan Troglodytes)

There are many parallels between human and nonhuman animal cognitive abilities, suggesting an evolutionary basis for many forms of cognition, including memory. For instance, past research found that two chimpanzees exhibited an isolation effect, or improved memory for semantically distinctive items on a list (Beran, 2011). These results support the notion that chimpanzees are capable of semantic, relational processing in memory, and introduce the possibility that other effects observed in humans, such as distinctiveness effects or false memories, may be present in nonhuman species. The Deese-Roediger-McDermott (DRM) paradigm is a commonly used task to explore these phenomena, and it was adapted for use with chimpanzees. We tested four chimpanzees for isolation effects during encoding, distinctiveness effects during recognition, and potential “false memories” generated by the DRM paradigm by presenting a serial recognition memory task. The isolation effect previously reported (Beran, 2011) was not replicated in this experiment. Two of four chimpanzees showed improved recognition performance when information about distinctiveness could be used to exclude incorrect responses. None of the chimpanzees were significantly impaired in the “false memory” condition. However, limitations to this approach are discussed that require caution about assuming identical memory processes in these chimpanzees and in humans.