Seth Pollak and colleagues (pictured) compared levels of the neuropeptides oxytocin and vasopressin in 18 four-year-old orphans and 21 age-matched control children. The controls had been raised in a typical family environment in Wisconsin, whereas the orphans had been adopted by an American family after spending the first year and a half of their lives in a Russian or Romanian orphanage where they experienced little human contact.
The researchers measured the children’s hormones at baseline; when they played with their mother (tickling and patting each other according to instructions given by a computer game); and when they played with a stranger.
Compared with controls, the orphans had lower baseline levels of vasopressin, a hormone thought to be specifically involved in recognising familiar people. Another difference emerged when the children played with their mother – oxytocin levels rose in the control children but not in the orphans. Oxytocin receptors are found in the brain’s reward pathways and it’s thought the hormone plays a role in feelings of security and protection.
The researchers said this showed “a failure to receive species-typical care disrupts the normal development of the oxytocin and vasopressin systems in young children. Perturbations in this system may interfere with the calming and comforting effects that typically emerge between young children and familiar adults who provide care and attention”. They explained these observations were consistent with reports that children reared in institutionalised settings continue to demonstrate social problems even after settling into an adopted family environment. However, they also cautioned that the current results were group effects – not all the orphans showed the hormonal differences, and children with lowered hormonal levels can go on to develop normal relationships.
But couldn’t the group difference in rising oxytocin levels be explained by the fact the controls were playing with their biological mother while the orphans were playing with their adopted mother? Lead author Alison Wismer Fries told the Digest “…our findings suggest that the neglected children's new primary attachment figures were not serving to activate the [hormonal] system the same way that typically reared kid's mothers do. And this can then help us explain the increased risk for affiliative problems in the post-institutionalized sample”.
Wismer Fries, A.B., Ziegler, T.E., Kurian, J.R., Jacoris, S. & Pollak, S.D. (2005). Early experience in humans in associated with changes in neuropeptides critical for regulating social behaviour. Proceedings of the National Academy of Sciences, USA, 102, 17237-17240.
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