Has Confirmation Bias Influenced How We View Ape Intelligence Compared To Us?


We may be misunderstanding the intelligence of our closest living relatives. Reut C/Flickr CC BY-NC-ND 2.0

We’re consistently told that apes are incredibly intelligent, but just not quite as intelligent as us. Decades of research has produced results that seem to confirm this conception about animal intelligence, but is it accurate?

One group of researchers has now suggested that the vast majority of studies that have assessed the intelligence of our closest animal cousin, the chimpanzee, and compared their intelligence to our own, are fundamentally flawed. Publishing their analysis in the journal Animal Cognition, the authors suggest that intelligence in apes is massively misunderstood.


Their argument centers on the history of our own ideas and perception of intelligence within our own species. Only a century ago the pervasive thought within Western science was that some groups of people – almost invariably separated by their ethnic and/or social background – were more intelligent than others. They thought that these differences were inherent, with a basis in genetics.

This notion was, during this period, supported by evidence and experiments carried out by the Western researchers who dominated science at the time. But the science was fundamentally flawed, in that it failed to take into account environmental inputs, failed to control for pre-test differences, and involved inconsistent testing circumstances.

But the root of all of these failings was quite simple: the scientists had confirmation bias. This is where a scientist undertakes an experiment with a preconceived idea of what outcomes they are looking for, and so when the results come in, they tend to interpret them as supporting their own theories even if such support is non-existent, or patchy at best.

Professor Kim Bard, one of the authors of the study, says that they have picked up on a similar bias within research comparing humans and ape intelligence. “In examining the literature, we found a chasm between evidence and belief,” said Bard in a statement. “This suggests a deep commitment to the idea that humans alone possess sophisticated social intelligence, a bias that is often not supported by the evidence."


One such example of this is an experiment that tested both apes and human children’s understanding of Western non-verbal communication, which resulted in the children outperforming the apes. The problems was, however, that the children had grown up in Western households, where they were exposed to non-verbal communications from a young age, while the chimps had grown up isolated from this experience.

It is therefore ambiguous whether the lower score achieved by the chimps is to do with their evolutionary histories, or learning experiences during development.

The authors suggest that there are ways to reduce this inequality, such as by making sure that all participants regardless of species, are trained in the same consistent way. This latest analysis may also help people understand that such a bias exists, and therefore take this into account.  

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