New research implies that the interactions an orangutan has with humans during its childhood may be a better predictor of its ability to problem-solve as an adult than almost any other factor.

Life history, particularly experiences of deprivation or enrichment, are known to have an impact on the cognitive development of orangutans. However even orangutans raised in the same environmental conditions will often display varying levels of cognitive ability, and explanations for this variation are still largely unknown.

With this in mind a recent study investigated whether orangutans from different backgrounds have different cognitive abilities, if they respond differently to novelty, and how they respond to humans. To test their cognitive abilities the orangutans were given sticks, some string, and a box containing honey which could be accessed in one of two ways: either through a straight channel using a stick, or through a curved channel that could only be accessed using string. The cognitive ability of the orangutans was then measured based on their response to the honey box and the difficulty of the puzzle’s various aspects, with the stick method assumed to be the easiest solution and the insertion of a string into the curved channel as the most difficult.

To assess how they responded to novelty, the orangutans were also given food that they had never encountered before and a toy which they had never seen before. The researchers also monitored how the orangutans responded to an unknown human.

When the researchers looked for patterns in their results, they discovered that the amount of interest the orangutans showed in the unfamiliar human was an excellent indicator of the orangutans’ ability to solve the honey puzzle—in other words, the more willing an orangutan was to approach or attempt to interact with the unfamiliar human, the more likely it was to solve the puzzle of the honey box. Human-oriented orangutans were also quicker to touch the unfamiliar food or the novel toy.

However, the apparent cognitive benefit of interaction with humans was found to occur only when this interaction had occurred when the orangutans were a young age; among orangutans that had frequent human contact as adults yet spent their childhood in the wild, the differences were not observed.

Sex, species, or background could not be used to predict an orangutan’s ability to solve the honey puzzle. This shows that enrichment alone is not responsible for the development of cognitive ability, as orangutans from a zoo background (which involves large amounts of enrichment) were not significantly better at the puzzle than orangutans from a rehabilitation centre, where artificial enrichment is avoided since frequently the ultimate aim is to return the animals to the wild.

Young orangutans learn from their mothers and other ‘expert’ orangutans in the wild, picking up the necessary skills by imitation. When in a captive setting humans replace the orangutan’s mother in a learning context, and as a result the ability to learn cognitive tasks is improved.

The results of this study imply that frequent interactions with people during the most influential period of a young orangutan’s life results in a more curious and less fearful adult orangutan, one better able to understand problem-solving tasks than an individual raised with little human contact. This has important implications for much of the research into primate intelligence and the authors encourage other scientists to take an individual ape’s human-related experiences into account when attempting to standardise cognitive comparisons across primates.

References

Damerius, L.A., Forss, S.I.F., Kosonen, Z.K., Willems, E.P., Burkart, Call, J., Galdikas, B.M.F., Liebal, K., Haun, D.B.M. & van Schaik, C.P. (2017). Orientation toward humans predicts cognitive performance in orang-utans. Scientific Reports 7, Article number: 40052.

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