Merry Christmas! (& Memes & Mirror Neurons)

So this is my last post before I’ll be heading home over the holidays.

As I tried to show in this post, it seems that the ability to imitate is crucial for learning a language. Most importantly, it also seems to be a major foundation of all human culture.

There is whole lot of research done in this field and there are hot discussions about the relationship between mirror neurons, imitation, Theory of Mind, language acquisition, language evolution, human cultural evolution, etc.

Memetics, for example, sees our ability to adopt cultural and cognitive patterns of behavior as mediated by our imitative abilities (Blackmore 2007). In 2005 Nick Chater and Susan Hurley published and edited Perspectives on Imitation: From Neuroscience to Social Science, a two volume monstrosity with 1024 pages covering Mechanisms of Imitation, Imitation in Animals, Imitation and Human Development as well as Imitation and Culture, This underlines the renewed appreciation of the importance of imitation as a fundamental property of cognition, instead of an uninteresting low-level phenomenon. (McEwen 2007)

The notion of a link between human culture and cognition on the one hand, and imitation and learning on the other, is of course not new – as we have seen in the passage of Puttenham’s Arte of Poesie I quoted in my last post on imitation. If you look up “imitative” in the OED, you find a 1777 quote by David Hume, who wrote that

“The human mind is of a very imitative nature”

as well as the assessment that

“At present, we are become an imitative, not to say a mimic, race” (in Gifford’s 1827 introduction to the plays of John Ford).

We can trace this notion as far back as to Aristotle, who in his Poetics, claimed that mimesis, the representation or imitation of a state in the world in the form of action, art, or speech, is a fundamental property of human cognition. Interestingly, he describes imitation as an “instinct of our nature” and writes that:

“the instinct of imitation is implanted in man from childhood, one difference between him and other animals being that he is the most imitative of living creatures, and through imitation learns his earliest lessons;”

As it seems, Aristotle’s assessment is indeed backed up by behavioral evidence. 30 years ago, Meltzoff and Moore (1977) found that 12 to 21-day old infants were able to imitate the experimenter’s facial gestures of mouth opening, lip protrusion and, tongue protrusion, as well as manual gestures such as the opening of the hand. In a follow-up study, they showed that even newborns who are less than 72 hours old are able to imitate these gestures (Meltzoff & Moore 1989). Interestingly, this tendency seems to disappear between two and three months of age. This is probably explained by the fact that autonomously controlled, spontaneus face-to-face social interaction (as a baby smiling at her mother, for example) kicks in around this time and infants start to communicate intentionally. (Myowa-Yamakoshi et al. 2004: 441)

Now is this a uniquely human trait?

Quite astonishingly, Myowa-Yamakoshi et al. (2004) found that chimpanzees who are less than 7 days old are also able to imitate the gestures of tongue protrusion, mouth opening, and lip protrusion.

As in humans, this tendency disappeared at two months of age. The authors conclude that
“like human neonates, chimpanzee neonates are born with the ability to match visually perceived oral gestures with a proprioceptive motor schemes .“ (Myowa-Yamakoshi et al. 2004: 440).

So what about other primates? Previously it was thought that only humans and apes posses these neonatal skills, but it seems that at 3 days of age, rhesus macaques are able to imitate lip smacking and tongue protrusion (Ferrari et al. 2006), facial gestures which later become important in social interaction (Gross 2006)

However, the macaques showed this behavior only a few days after birth and after that it vanished. This may be due the fact that motor as well as cognitive development in macaques is much more rapid in macaques than in the higher apes. It thus seems that the more advanced human imitation capacities built on these imitative foundations that must have been present at the time our lineage split from that of macaques, namely 25 million years ago.
Interestingly, macaques were the first species in which mirror neurons – neurons that fire both during the performance as well as during the observation of an action – were found, and hopefully there will be more studies on the neural basis of imitation in macaques.

Quite Remarkably, adult macaques are also able to notice when someone else is imitating their actions (e.g. a human experimenter), but it is unclear whether they are able to grasp the fact that the experimenter is intentionally imitating them, or if they just recognize it implicitly (Paukner et al. 2005). In the second case, the macaques would just exhibit this knowledge via metacognition, i.e. the awareness of some inner state, something which macaques seem to be able to do.
Evidence for metacognition in macaques comes from research done by H.S. Terrace and his team, who taught their macaques a matching game, and then offered them the options to either play the game and get some food if they won and nothing if they lost, or the option to not play the game and get less food. Interestingly, sometimes the macaques chose the latter, option, and sometimes they chose the former, but if they chose the first option, they performed pretty well, indicating that the macaques had a means of assessing how accurate they were at getting the game right. In another experimental setting, macaques also learned to ask for hints if they otherwise had to solve the problem by trial and error, again indicating that they had some metacognitive means of assessing what they knew and what they didn’t (Kornell et al. 2007).
It is much more questionable if macaques exhibit metarepresentation, i.e. the awareness of mental states of others (Hurford 2007: 35)

This of course taps into the discussion of which primates exhibit a Theory of Mind, or an awareness of the mental states of others, and whether the transition from nonhuman to human minds should be seen as continuous or discontinuous. The two main camps in this debate are that of Povinelli and his colleagues on the one side, who argue that nonhuman primates do not exhibit abstract inferences of others mental states, and that there is a qualitative gap between human and nonhuman cognition (Povinelli & Vonk 2003), and Tomasello and his team on the other side, who argue that chimpanzees are able to understand some psychological states to a certain degree, and that human cognition should be seen as much more continuous (Tomasello et al. 2003). It seems as if Povinelli and his colleagues are just about to launch their next major attack (to be publish in the journal Behavioral and Brain Sciences in 2008) awe-inspiringly called “Darwin’s mistake: Explaining the discontinuity between human and nonhuman minds” . As BBS consists of the target article along with 25 or so commentaries other researchers, I’m really interested in how this will turn out.

For now it is quite interesting enough (and also somewhat amusing) how both parties assess the importance of the debate:

Whereas Tomasello et al. (2003) claim that:

“At issue is no less than the nature of human cognitive uniqueness” (Tomasello et al. 2003: 156)

Povinelli et al. take a much more relaxed stance:

"the idea that theory of mind is the ‘holy grail’ of comparative cognition needs to be abandoned. Neither chimpanzees nor evolutionary theory will be insulted if the very idea of ‘mental states’ turns out to be an oddity of our species’ way of understanding the social world.“ (Povinelli et al. 160)

Dang, I still haven’t posted about either the Lyons et al. (2007) paper or the genetic differences between humans and chimpanzees. But I will do so next year. Promise. Cross my Heart and Hope to Die. As an apology, here’s a link to a great song by Jonathan Coulton, performed live in front of an audience of (judging by the chorus) zombies. Gotta love that.

So merry Christmas & Happy New Year, and see you in 2008.

References:

Blackmore, Susan. 2007. “Those dreaded memes: The advantage of memetics over “symbolic inheritance.” Behavioral and Brain Sciences 30.4: 365-366.

Ferrari PF, Visalberghi E, Paukner A, Fogassi L, Ruggiero A, et al. (2006) Neonatal imitation in rhesus macaques. PLoS Biol 4(9): e302. DOI: 10.1371/journal.pbio.0040302

Gross L (2006) Evolution of Neonatal Imitation. PLoS Biol 4(9): e311 doi:10.1371/journal.pbio.0040311

Hurford, James M. 2007. The Origins of Meaning: Language in the Light of Evolution. Oxford: OUP.

Kornell, Nate, Son, Lisa K. and Herbert S. Terrace. 2007. “Transfer of Metacognitive Skills and Hint Seeking in Monkeys. Psychological Science” 18.1: 64-71.

McEwen, Fiona. 2007. “Review: Perspectives on Imitation: From Neuroscience to Social Science.” Mind & Language, 22.2 April : 207–213

Meltzoff AN, Moore MK .1977. Imitation of facial and manual gestures by human neonates. Science 198: 75–78.

Meltzoff AN, Moore MK (1989) Imitation in newborn infants: Exploring the range of gestures imitated and the underlying mechanisms. Developmental Psychology 25: 954–962

Myowa-Yamakoshi M, Tomonaga M, Tanaka M, Matsuzawa T .2004. “Imitation in neonatal chimpanzees (Pan troglodytes).” Developmental Science 7: 437–442

Paukner A, Borelli E, Visalberghi E, Anderson JR, Ferrari PF (2005) Macaques (Macaca nemestrina) recognize when they are being imitated. Biology Letters 1: 219–222.

Povinelli, D.J. and Vonk. J. (2003) Chimpanzee minds: Suspiciously human? Trends in Cognitive Sciences, 7.4, 157–160.

Tomasello, Michael, Josep Call and Brian Hare. 2003. Chimpanzees understand psychological states – the question is which ones and to what extent. Trends in Cognitive Sciences, 7- 153-156.