Monkey self-recognition? Not so fast!

Last week I posted a story about an experiment suggesting monkeys can recognize themselves in the mirror. One of the experts I contacted was Peter G. Roma, who was the lead author of a 2007 paper that failed to find evidence for this kind of self-recognition. Roma responded today with an interesting response, which I’m posting here, and at the end of the original post...

Although the video samples are provocative, I cannot agree with the conclusion (and title) of the paper.

The lack of social behaviors towards the mirror is irrelevant because the monkeys all had an extensive history with mirrors prior to the study, so there was no reason to expect social responses after years of habituation to reflective surfaces. To anthropomorphize, they may still think the monkey in the mirror is another animal, but over the years they’ve learned that he’s harmless.

The examples of putative genital viewing were not convincing either. The authors repeatedly asserted that the monkeys used the mirrors to view areas they could not see directly, but monkeys can see their genitals unaided, and they play with them all the time with or without mirrors! Even the video samples show the monkeys looking at their genitals directly then viewing the same area(s) in the mirror. This is why scientists do the mark test!

In my view, the most compelling evidence was the first video of the monkey touching the head implant while holding the mirror. There is no doubt that the monkeys could not see the implant without a reflective surface, but the key here is whether or not this self-examination behavior occurred more frequently in the presence of the mirror vs. without. The authors report increased incidence of touching “unseen” areas in the presence of the mirror (figure 2C), but these data include touching the cranial implant and the genitals. I suspect these data are artificially inflated by what the authors perceive as mirror-guided genital examination, which even in the video examples did not appear to be anything more than typical stereotyped “acrobatic” behaviors often seen in individually-housed rhesus monkeys. The authors provide no data on the frequency of just cranial implant touching with vs. without mirrors, and no visual evidence except for the single incident from the video. Why wouldn’t they report the number of implant explorations independently of the genital viewing?

My primary concern is that all monkeys failed the mark test, and the strongest apparent evidence of mirror self-recognition (MSR) was only seen in two monkeys following cranial surgery–a manipulation with strong tactile cues that could elicit exploration regardless of the mirror’s presence. Their argument rests largely on the assertion that the cranial implant is a “super mark” that somehow awakened a latent ability in the monkeys to self-recognize, but it’s unclear why the implant would be more visually salient than a brightly contrasting color marking on the face. The more parsimonious conclusion is that the tactile sensation of the implant was enough to elicit exploration, but even then, the authors provide no evidence that implant exploration occurred more frequently in the presence of the mirror vs. without.

If the authors’ hypothesis is true that a cranial implant serves as a “super mark,” then their procedures warrant replication, which frankly they should have done before making such a bold assertion. Currently within the Order Primates, the overwhelming preponderance of evidence still limits MSR and the fundamental cognitive precursor to a “sense of self” to the apes.

10 thoughts on “Monkey self-recognition? Not so fast!

  1. This is a ridiculous argument. Much dumber animals recognize themselves in mirrors, unquestionably. I used to have a cat that I know recognized itself in the mirror because it ignored the image completely – if she thought there was another cat right there, she would attack it immediately (very territorial – she attacked a small dog once, too).

    A moment’s consideration makes it obvious that an ability to recognize one’s own reflection is pretty important to any animal which might happen upon a standing body of water to drink from.

  2. @Thanny, this is the reason for the mark test. If they just know to ignore an animal that they see in that surface, whether water or mirror, we can’t actually tell the difference. Instinctively, we’d guess it’s easier to just figure out that the image is you, but humans are strange, and what’s intuitive for us may not be for other animals.

  3. Thanny, you’re also assuming there’s a linear hierarchy of intelligence, which isn’t the case. Parrots are less intelligent than people, right? Well, parrots can “count on sight” (in other words “know how many there are without having to count up 1.. 2.. 3..) much larger numbers than we can and in that sense are better than us. Mirror self recognition is an important indicator of cognitive capacity, but it is not the only indicator…

    Your experience with your cat also has other explanations than self recognition. Check out the animal cognition literature and you’ll see that scientists have done a lot of work in this area that cannot be so easily dismissed by an anecdote about a pet.

  4. @Thanny, you’re ignoring scent (among other things, such as airflow, sounds, contiguousness with other visual stimuli, etc). Maybe your cat just knew there was no cat there at all, and so the question of its identity was irrelevant…

    This is actually a problem I have with the MSR test; maybe animals that fail just don’t care who or what is in the mirror because they know it is not real (and/or only show interest because something ‘there’ to one sense but not to the full sensory apparatus is anomalous).

    A question for those who might know: has anyone done any tests with false mirrors – say, with a fully sealed (scentproof!) window onto a replica room – and tested responses to different visual stimuli under those conditions?

  5. Interesting. The MSR test is intriguing but is sometimes used, improperly in my view, as a marker of general intelligence, rather than as a particularized quirk of behavior. Tool-making used to be a marker of general intelligence (and thereby of human superiority) until it became obvious that other animals like Caledonia crows and chimps fishing for ants are quite adept at tool-making. Sort of like how in earlier generations (less today), whether a culture used the wheel or not was considered a definitive marker of ‘primitiveness” or “advancedness.”

    Mirrors abound in nature. They are called water. Any animal dipping its head down in a pond or waterhole to take a drink is going to see its reflection staring back at them. Obviously, they ‘know’ the reflection is just their reflection and is not another real animal staring up at them. If not, this would make taking a drink a very surreal experience for an animal.

  6. Perhaps someone here can help me out with a question. One of Roma’s arguments is that Chimps who’d been acclimated to a human environment containing mirrors should not be included in the results. As stated in this blog’s previous entry on the mirror test, human children often fail the self-recognition test until they reach a specific point in development. Do we just assume that an adult human, previously detached from modern society, would pass the mark test “in the wild,” or is there data to back this up? Put another way, is there evidence that humans would pass the mark test having reached adulthood in an environment devoid of reflective surfaces?

  7. Sometimes I get the feeling that experts like Peter G. Roma are trying a little too hard. To assert their knowledge and relevance. “Aha, there’s a 0.006% chance that the experiment is flawed because there was a dirty spot on the mirror!” Seems to me like the mirror test is pretty good.

    For instance, he asserts that because a monkey can see it’s own genitals, the mirror result of a monkey looking at their genitals means nothing. Or alternatively, does not mean what the study authors claim. Really? Has Roma established anything with this assertion? It sounds like hollow argumentation to me.

    I believe that millions of primates look at their genitals in mirrors every day. Why? Can they not see their own genitals? Of course they can. The point is, it’s a different point of view, that said primate cannot ordinarily see. Without a mirror.

    My point of view is that if an animal observes and manipulates their own body while looking in the mirror, they are making a connection between self and image. If they attempt to manipulate the mirror itself (properly speaking, the image in the mirror), they fail the test.

    Also, complaining that animals have experience with the mirror, is only slightly less persnickety. While it may make the test more challenging, it does not absolutely disqualify the test from consideration. The main challenge, I would think, would be to interest the animal for long enough to perform a meaningful test.

    Since the activity does not directly relate to the essentials of life (food, shelter, mating), it is important that they spend any time at all on it. It cannot be explained away by bonding and group dynamics. It does not fit with play activity. I am treading outside of my area of expertise, but it does not even sound like the stereotyped activities of any animal I have ever heard of.

    In Roma’s zeal not to anthropomorphize, he reveals something perhaps a little more than he realizes. Why is it anthropomorphic logic to “think the monkey in the mirror is another animal…”. It is basic biology for a species to recognize others of it’s species, however primitive that recognition mechanism is. Friend versus foe, kin versus stranger, potential mate versus everything else.

    Occam’s razor says the most likely explanantions, by far, are either that the animals think the image is another monkey, or that the image is themselves. To suggest otherwise becomes tendentious and outlandish. “Maybe the animal thinks it’s a vertical pool of water!” “Maybe the animal thinks it’s the eye reflection of a giant creature consisting of only 1 eye!” “Maybe the animal thinks it’s an n-dimensional portal to a parallel universe!”

    Or maybe the commentator is just trying to prove how clever they are. Huh.

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