Urban living and access to schooling shapes how kids perceive size, research indicates

Children who have grown up in urban environments fall for a well-known optical illusion more often than kids from remote cultures - because access to schooling has changed the way we look at pictures, a Goldsmiths, University of London study suggests.

Researchers from the Department of Psychology showed children from 3-years-of age the Ebbinghaus illusion on a computer screen.

Participants were from remote Himba villages in Northern Namibia, or from a town called Opuwo – the nearest urban development to the Himba. Data from UK residents, collected in an earlier study, was also analysed.

The illusion shows two circles placed near to each other, with one surrounded by large circles and the other surrounded by small circles. For many people, the central circle surrounded by large circles will appear smaller than the central circle surrounded by small circles, even when this is not actually the case.

In UK children this illusion develops in early childhood. When judging which of the target circles was larger, 9-10 year-old UK kids were fooled by the illusion and made more mistakes than younger UK children.

But the Himba children were not much fooled at all until they were of secondary school age.

From 9-10 years, traditional Himba children were much more immune to the illusion than British kids, correctly stating more often which circle was larger. This age group of Himba children also beat the illusion more often than the urban Namibian children who had received formal schooling.

In fact, the study authors found that the number of years urban Namibian children were at school was the main factor predicting how much children were fooled by the illusion.

The 50 Himba children who took part (from a total of 336 participants) were from a community of semi-nomadic herders who have limited contact with Western culture and artefacts. Their ages had to be estimated, as the community does not usually keep birth records.

Why does this happen?

The researchers believe that Western children have developed to process visual context (in this case, the circles surrounding the central circle) differently to Himba children because of the way they’ve engaged with pictures and print as they’ve grown.

The study showed that while UK children are processing context by the age of 9 or 10, Himba children are completely unaffected by it.

It’s likely that cluttered urban environments impact on the development of a child early in life, but pictorial and printed materials become particularly relevant in middle-childhood around the age of 9-10 – the same point at which a divergence between Himba and UK children was observed in the Ebbinghaus illusion test.

Lead researcher Professor Andy Bremner, Head of Psychology at Goldsmiths, explains:

We believe that living in a cluttered urban environment and going through formal schooling plays a role in changing the way we involve context in our visual perceptions.

“There are some well-known differences in the way different cultures perceive visual shapes and patterns, but our study goes further in providing an account of how these differences emerge through the interaction of nature and nurture in early development.

“We found that development of differences between the cultural groups was complete by about 10-years of age, which helps us hone in on one particular explanation.

"Rather than being due to differences in how we focus our attention - something that continues to develop in later childhood - we believe that cross-cultural differences in the Ebbinghaus illusion are due to how we take context into account when we look at the world.

“Perceiving and understanding context isn’t a universal human feature, but something that develops quite differently depending on where or how you grow up.”

'Effects of Culture and the Urban Environment on the Development of the Ebbinghaus Illusion' by Andrew J. Bremner, Jan de Fockert, Karina J. Linnell, Jules Davidoff (Goldsmiths), Martin Doherty (University of East Anglia) and Serge Caparos (Universite de Nimes) is published in the journal 'Child Development'.