Rhesus monkeys know when they remember

Abstract

Humans are consciously aware of some memories and can make verbal reports about these memories. Other memories cannot be brought to consciousness, even though they influence behavior. This conspicuous difference in access to memories is central in taxonomies of human memory systems but has been difficult to document in animal studies, suggesting that some forms of memory may be unique to humans. Here I show that rhesus macaque monkeys can report the presence or absence of memory. Although it is probably impossible to document subjective, conscious properties of memory in nonverbal animals, this result objectively demonstrates an important functional parallel with human conscious memory. Animals able to discern the presence and absence of memory should improve accuracy if allowed to decline memory tests when they have forgotten, and should decline tests most frequently when memory is attenuated experimentally. One of two monkeys examined unequivocally met these criteria under all test conditions, whereas the second monkey met them in all but one case. Probe tests were used to rule out ''cueing'' by a wide variety of environmental and behavioral stimuli, leaving detection of the absence of memory per se as the most likely mechanism underlying the monkeys' abilities to selectively decline memory tests when they had forgotten.

Not knowing what one knows: A Meaningful failure of metacognition in capuchin monkeys.

“…Furthermore, they were more likely to escape the trial on special trials in which the sample was never presented (and therefore could not be remembered). These results are similar to Hampton's (2001) study with macaques and support the claim that the capuchin monkeys were aware of their own ignorance about the correct response. But there were still limitations that complicated that interpretation.…”

“…From "The Comparative Psychology of Uncertainty Monitoring and Metacognition," by J. D. Smith, W. E. Shields, and D. A. Washburn, 2003, Behavioral and Brain Sciences, 26, p. If monkeys genuinely demonstrate metacognition through their behavior, then such metacognition should express itself across a variety of different tasks that provide converging evidence to support the weight of the claim for private metacognitive capacities in animals. Such tasks include the uncertainty response already discussed (e.g., Smith et al, 1997), information-seeking responses in computerized tasks (e.g., Beran & Smith, 2011), responses that show confidence in prior decisions (e.g., Beran et al, 2015), and metamemory tasks in which the animal may have forgotten some previously learned material, and may need to decline a memory test or to seek out additional information (e.g., Basile et al, 2015;Hampton, 2001;Marsh & MacDonald, 2012a). Information-seeking tasks involve introducing subjects to trials in which they sometimes need to proactively seek visual information to observe in order to correctly respond.…”

“…For both cashout responses and proportion correct, progressively darker lines depict increasingly risky situations in which there were more coins/rewards at stake. Other metamemory tasks, such as that developed by Hampton (2001), also provide a strong test against environmental cues controlling the UR. Hampton had macaques work in a delayed matching-tosample task and reported that the monkeys avoided taking more tests at long delay intervals when the sample was most likely to have been forgotten, but also on trials in which the sample was never presented.…”

Information Seeking in Animals: Metacognition?

“…Experiments reported during the past 15 years have led to the suggestion that metacognition may be found in nonhuman primates (Hampton, 2001;Hampton, Zivin, & Murray, 2004;Kornell et al, 2007;Smith, Shields, Allendoerfer, & Washburn, 1998;Smith, Shields, Schull, & Washburn, 1997;Smith, Shields, & Washburn, 2003) and in a bottlenosed dolphin (Smith, Schull, Strote, McGee, Egnor, & Erb, 1995). These experiments generally require the subject either to make a psychophysical response or to take a memory test.…”

Getting It Together: Psychological Unity and Deflationary Accounts of Animal Metacognition

“…That is, evidence of metacognition would almost surely be evidence of phenomenological consciousness. Indeed, over the last 20 years, evidence has appeared that seems to show that some animals-notably some monkeys (rhesus macaques, not capuchins), dolphins, rats, and baboons-do metacognize (Smith et al 1997;Washburn, Smith, and Shields 2006;Hampton 2009;Kornell, Son, and Terrace 2007;Hampton 2001; for dolphins : Smith et al 1995;for rats: Foote and Crystal 2007; for baboons : Malassis, Gheusi, and Fagot 2015). They can stop in their tracks, reflect on what they have seen and done, and even decide how much weight to give to their confidence that they do (or do not) know the answer to a question.…”