Matkivatko pikkuvauvat?

Monissa psykologian kirjoissa – sekä lasten kehittymistä että ihmislajin yleisiä taipumuksia käsittelevissä osioissa – kerrotaan vastasyntyneiden matkivan aikuisten ilmeitä. Kyse on yleensä Andrew Meltzoffin tutkimuksesta 1970-luvulta. Useimmiten mainitaan kielen työntäminen ulos suusta, toisinaan mustavalkokuvien kanssa. Tuore tutkimus kyseenalaistaa vastasyntyneiden matkimiskyvyt.

Tässä ensin aiheeseen liittyviä mainintoja joistakin kirjoistani:

Francesca Morganti ym. toim.: Enacting Intersubjectivity (2008):

Meltzoff, in his life-long research about infant imitation, found that newborns - even only 42 minutes old - demonstrate successful facial imitation. Moreover he found that 12–21-day-old infants can imitate four different adult gestures: lip protrusion, mouth opening, tongue protrusion and finger movement. Interestingly, the newborns’ first response to seeing a facial gesture is the activation of the corresponding body part: it is as if young infants isolate what part of their body to move before how to move it (organ identification).

Sue Carter ym. toim.: Attachment and Bonding (2005):

Perhaps not surprisingly, right from birth human infants seek out human faces and initiate contact with others. Remarkably early in devlopment, babies imitate faces, smile, and laugh in ways that no other ape living in the wild to our present knowledge does.

Pascal Boyer: Religion Explained (2001):

Incidentally, the fact that an infant can imitate adults' facial gestures (sticking out the tongue, pursing the lips, frowning, etc.) shows that the newborn's brain is equipped with highly specialized capacities.

Sarah Blaffer Hrdy: Mothers and Others (2009):

Meltzoff together with Keith Moore reported that some human babies as young as 12 hours old possess the innate ability to imitte others. - - - Caught in the right mood, a baby will often respond to tongue protrusions by sticking out her tongue. After repeating his experiments with even younger newborms, Meltzoff quipped, ”You can’t get much younger than 42 minutes old.” Meltzoff was convinced that he had documented that ”a primitive capacity to imitate is part of the normal child’s biological endowment.”

Philippe Rochat: Others in Mind (2009):

If infants from birth show a propensity to imitate facial expressions such as tongue protrusion or basic emotions such as joy or sadness, by the second month they demonstrate systematic matching that denotes a novel sense of how they relate to the model they imitate. In a one experiment researchers showed, for example, that six-week-olds tend to copy systematically the orientation of the tongue protrusion of an adult model pulling her tongue either to the right or to the left, as opposed to midline. This imitative response of the infants indicates that not only do they reproduce the global tongue protrusion act, something they are capable of from birth, they also approximate the directionality of the modeled tongue movements.

Alison Gopnik: Filosofinen vauva (2010):

Andy Meltzoff on matkimisen tutkimuksen kuningas. 1970-luvulla hän osoitti, että kirjaimellisesti syntymästään lähtien vauvat matkivat toisten ihmisten eleitä ja tekoja.

Andrew Meltzoff on tehnyt uraauurtavaa tutkimusta vauvojen kognitiosta, mutta tässä nimenomaisessa kysymyksessä tutkimustulokset ja niiden myöhempi raportointi saattavat olla liioiteltuja. Ihmisvauvoilla luultavasti on muita kädellisiä suurempi tarve tulkita ja havainnoida lajikumppanien mielialoja ja aikomuksia – ihmislajihan nojaa lisääntymisessään poikkeuksellisen paljon muilta tulevaan apuun –, mutta vastasyntyneen kyvyt eivät matkimiseen näytä yltävän. Matkiminen mahdollisesti alkaa kunnolla vasta muutaman kuukauden ikäisenä. Tässä tuoreen artikkelin yhteenveto:

Oostenbroek ym. (2016): Comprehensive Longitudinal Study Challenges the Existence of Neonatal Imitation in Humans. Current Biology. Vol 26(10) s. 1334–1338.

Human children copy others’ actions with high fidelity, supporting early cultural learning and assisting in the development and maintenance of behavioral traditions. Imitation has long been assumed to occur from birth, with influential theories placing an innate imitation module at the foundation of social cognition (potentially underpinned by a mirror neuron system). Yet, the very phenomenon of neonatal imitation has remained controversial. Empirical support is mixed and interpretations are varied, potentially because previous investigations have relied heavily on cross-sectional designs with relatively small samples and with limited controls. Here, we report surprising results from the most comprehensive longitudinal study of neonatal imitation to date. We presented infants (n = 106) with nine social and two non-social models and scored their responses at 1, 3, 6, and 9 weeks of age. Longitudinal analyses indicated that the infants did not imitate any of the models, as they were just as likely to produce the gestures in response to control models as they were to matching models. Previous positive findings were replicated in limited cross-sections of the data, but the overall analyses confirmed these findings to be mere artifacts of restricted comparison conditions. Our results undermine the idea of an innate imitation module and suggest that earlier studies reporting neonatal imitation were methodologically limited.

Kriittisiä puheenvuoroja matkimistaipumuksen kulttuurista merkitystä kohtaan on esittänyt esimerkiksi Juan Carlos Gómez kirjassaan Apes, Monkeys, Children an the Growth of Mind (2004):

The cultural learning debate, as posed in the last years, may have been seriously misguided and rooted upon a quasi anecdotal misconception of human social learning as essentially imitative in the narrow sense. Imitation of actions is just one more process at play in cultural transmission, an one that may have originally evolved not as an adaptation for more effective transmission of skills, but as a mechanism for interaction and communication.

Niin tai näin, päivitetäänköhän Wikipediaa juurikaan tällaisten uusien tutkimusten osalta?

PS. Hesarissa 20.8. on pieni juttu matkapahoinvoinnista. Siinä neurologi Matti Ilmavirta on eri mieltä teoriasta, jonka mukaan matkapahoinvointiin liittyvässä oksentamisessa olisi kyse myrkytystä vastaan kehittyneestä ominaisuudesta. Teorian mukaan toksiinit ovat tuottaneet aivoille samanlaisen ristiriidan kuin minkä voi kokea esimerkiksi keinuvan laivan hytissä: aivot saavat viestejä sekä liikkeestä (laivan keinunta) että liikkumattomuudesta (hytin seinät pysyvät paikoillaan). Ja aivot teorian mukaan tulkitsevat tilanteen myrkytystilaksi. Avoin kysymys on, onko ihmisen evoluutioympäristössä ollut riittävän usein myrkyllisten marjojen ja sienten tai pilaantuneen ruoan aiheuttamia ja oksentamisella parantuvia myrkytystiloja, jotta matkapahoinvointioksentaminen olisi kehittynyt sopeutumaksi? Mielenkiinnolla odotan tulevia tutkimuksia. Wikipedia (5.9.2016) selittää ilmiötä seuraavasti:

The most common hypothesis for the cause of motion sickness is that it functions as a defense mechanism against neurotoxins. The area postrema in the brain is responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When feeling motion but not seeing it (for example, in a ship with no windows), the inner ear transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. As a result of the discordance, the brain will come to the conclusion that the individual is hallucinating and further conclude that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin. Treisman's indirect argument has recently been questioned via an alternative direct evolutionary hypothesis, as well as modified and extended via a direct poison hypothesis. The direct evolutionary hypothesis essentially argues that there are plausible means by which ancient real or apparent motion could have contributed directly to the evolution of aversive reactions, without the need for the co-opting of a poison response as posited by Treisman. Nevertheless, the direct poison hypothesis argues that there still are plausible ways in which the body's poison response system may have played a role in shaping the evolution of some of the signature symptoms that characterize motion sickness.An alternative theory, also known as the Nystagmus Hypothesis, has been proposed based on stimulation of the Vagus nerves resulting from the stretching or traction of extra-ocular muscles co-occurring with eye movements caused by vestibular stimulation. There are three critical aspects to the theory: first is the close linkage between activity in the vestibular system, i.e., semicircular canals and otolith organs, and a change in tonus among various of each eye's six extraocular muscles. Thus, with the exception of voluntary eye movements, the vestibular and oculomotor systems are thoroughly linked.Second is the operation of Sherrington's Law describing reciprocal inhibition between agonist-antagonist muscle pairs, and by implication the stretching of extraocular muscle that must occur whenever Sherrington's Law is made to fail, thereby causing an unrelaxed (contracted) muscle to be stretched.Finally is the critical presence of afferent output to the Vagus nerves as a direct result of eye muscle stretch or traction. Thus, 10th nerve stimulation resulting from eye muscle stretch is proposed as the cause of motion sickness.The theory explains why labyrinthine defective individuals are immune to motion sickness; why symptoms emerge when undergoing various body-head accelerations; why combinations of voluntary and reflexive eye movements may challenge the proper operation of Sherrington's Law; and why many drugs that suppress eye movements also serve to suppress motion sickness symptoms.