Orphaned chimpanzee infants given special ‘mothering’ by humans are more advanced than the average child at nine months of age.
In the first study to examine the effect of different types of care for infant chimpanzees on cognition, researchers found chimpanzees who were given extra emotionally-based care were more cognitively advanced than human infants.
Humans overtake chimpanzees in development terms as they grow older but the study sends stark warnings that looking after just an infant’s physical needs is likely to result in a child who is maladjusted, unhappy and under-achieving.
The study was carried out by psychology expert Professor Kim Bard, of the Centre for the Study of Emotion at the University of Portsmouth.
She said: “The attachment system of infant chimpanzees appears surprisingly similar to that found in human infants. Early experiences, either of warm, responsive care-giving or of extreme deprivation, have a dramatic impact on emotional and cognitive outcomes in both chimpanzees and humans.
“Parental sensitivity is an important factor in human infant development, contributing to emotionally and cognitively strong children, and it would seem the same is true for great apes, as well.”
Professor Bard studied 46 chimpanzees in the Great Ape Nursery at the Yerkes National Primate Research Centre in Atlanta, America, in the 1980s and 1990s. The chimpanzees were in the nursery because their mothers’ maternal skills were so inadequate the infants were at risk of dying.
She found that chimpanzees given 20 hours a week of responsive care, which looks after the emotional and physical development, were happier, more advanced and better adjusted than chimpanzees given standard institutionalised care which meets just their physical needs.
She said: “Those given responsive care were less easily stressed, less often attached to ‘comfort blankets’, had healthier relationships with their caregivers and were less likely to develop stereotypic rocking. They were also more advanced intellectually than chimpanzees reared with standard institutionalised care.”
The responsive care was given by human caregivers who would play, groom, feed and interact with the infants. The caregivers focused on nurturing emotional and communicative well-being, similar to that found in the parenting behaviour of well adjusted mother chimpanzees. This level of care lasted through the first year of life and the chimpanzees’ development was assessed at various stages using the same tests as those used to assess development and attachment in human infants.
The chimpanzees raised with standard institutionalised care were more likely to show signs of ‘disorganised attachment’, including rocking, or clasping themselves or a blanket, instead of seeking comfort from a carer when distressed. They also showed other contradictory behaviours such as being distressed in the absence of a carer but ‘freezing’ when the main carer returned after a brief absence.
In human infants, ‘disorganised attachments’ are seen in children whose parents have unresolved losses or other trauma, and/or when the infants are abused or neglected.
Dr Bard said: “Responsive care, which meets infants’ emotional as well as physical needs, stimulates cognitive and emotional development.
“Infant chimpanzees who were given this care were more advanced and less likely to develop attachment to things like security blankets than chimpanzees whose care was only meeting their physical needs.”
It is the first study to investigate individual differences in attachment relationships in great apes and is also the first intervention study with non-human primates evaluating the effects of two types of human care, differing in quality and quantity, on infant chimpanzees’ cognitive development and attachment security.
The study was co-authored by Professor Bard and Krisztina Ivan of the University of Portsmouth’s Centre for the Study of Emotion and Professor Marinus van IJzendoorn and Dr Marian Bakermans-Kranenburg of the Centre for Child and Family Studies at Leiden University in the Netherlands. Partial funding was provided by the European Commission for the Feelix Growing project. The study is published in Developmental Psychobiology.
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