Recently, a group of scientists including prominent mirror neuron researcher, Vittorio Gallese, published an article purporting to demonstrate social interaction between identical twin fetuses in the uterus (at a time in their development before they have even the most basic reflexes). While their conclusions were highly dubious, their study is not actually the focus of this blog entry. Instead, I want to address something that they bring up in the fourth sentence of their introductory remarks. Castiello et al. (2010) state that, "even hours after birth, newborns have been found to show preparedness for social interaction that, among other things, is expressed in their imitation of facial gestures" (p. 1).
It seems that nearly every researcher in the fields of embodiment and comparative psychology has accepted this idea, that neonates are wired to imitate, wholeheartedly, yet the evidence cited to support this position is surprisingly scant. Namely, researchers cite the iconic work of Meltzoff and Moore (1977) published in Science, which suggested that newborns are capable of imitating facial gestures. Specifically, it was suggested that infants were capable of imitating both tongue protrusions (TPs) and mouth opening (MO). You may have seen Figure 1 from Meltzoff and Moore (1977) in many textbooks.
In their primer on infant cognition, Moll and Tomasello (2010) interpreted this finding as evidence that, “infants had an innate understanding that other persons are ‘like me,’ which constitutes a critical basis for deeper intersubjective understanding later in life” (p. R873). Is this interpretation warranted, though?
A good amount of research has been carried out since Meltzoff and Moore’s initial publication, and much of it indicates that Meltzoff was way off base, yet this research has captured almost no attention. It’s been all but ignored by mirror neuron researchers who cite the Meltzoff work as if it is without question. I contend that Meltzoff’s work has been thoroughly debunked, and I’d like to briefly lay out some of the evidence here.
The first question is, can Meltzoff’s findings be relicated? The answer: not exactly. Anisfeld (1996) reviewed the literature on infant imitation, reporting that MO imitation (and other frequently investigated varieties of imitation) is rare while TP imitation is robust. See a problem yet? Infants only imitate one behavior? Awfully strange, considering that imitation of this one behavior serves no discernible evolutionary purpose. That leads to the second question: Why might an infant appear to be imitating this behavior?
The answer to this question is actually quite interesting. It’s important to note that TP imitation is relatively short-lived. Infants quit imitating tongue protrusions around the age of 2 or 3 months (Jacobson, 1979). Oddly enough, this decline happens to coincide with the development of reaching behaviors. Thus, up until this development, infants primarily interact with the world via their mouths. Might it be the case that TPs are simply the result of stimulation? Indeed, in a beautiful set of experiments, Jones (1996) showed that a blinking light (a completely non-social stimulus) elicited tongue protrusions (at least for infants who showed interest in the blinking light) and that infants were more attracted to faces with a protruding tongue than faces with an open mouth. This points to tongue protrusion as a result of stimulation, not imitation. Finally, she showed that the development of reaching behavior coincided with the decline of TP responses to interesting objects within the infants’ reach.
Thus, imitation of TPs is simply coincidental, and it is unlikely to be imitation, at all. Are we wired to imitate or do we learn to imitate? Given the first option’s foundation on grains of sand, I lean toward the second option.
Anisfeld, M. (1996). Only tongue protrusion modeling is matched by neonates. Developmental Review, 16, 149-161.[Link to Abstract]
Castiello, U., Becchio, C., Zoia, S., Nelini, C., Sartori, L., Blason, L., et al. (2010). Wired to be social: The ontogeny of human interaction. PLoS One, 5, e13199.[Link to Open Access Entry]
Jacobson, S. W. (1979). Matching behavior in the young infant. Child Development, 50, 425-430.[Link to PDF]
Jones, S. S. (1996). Imitation or exploration? Young infants' matching of adults' oral gestures. Child Development, 67, 1952-1969.[PDF]
Meltzoff, A. N., & Moore, M. K. (1977). Imitation of facial and manual gestures by human neonates. Science, 198, 75-78.[PDF]
Moll, H., & Tomasello, M. (2010). Infant cognition. Current Biology, 20, R872-R875.[Link to Abstract]