Babies see colour without interference from the brain's language centre.
Babies and adults use opposite sides of their brains to process colours. And the switch is due to the influence of language, a study suggests.
It is well known that in adults, perception of colour is processed predominantly by the left hemisphere, which is also where most people process language. Studies have shown that the language one speaks can have an impact on the colour one sees.
Paul Kay at the University of California, Berkeley, and his colleagues wanted to know if this left-side bias was carved out by the development of language in the left hemisphere, or whether it was present even before language is acquired.
So they tested two age groups — adults and 4–6-month-old babies — with the same colour-perception task. A coloured target is shown at a randomly chosen location on a different coloured background, and the researchers watch to see how long it takes the participant to shift their attention to the target's location.
Adults reacted more quickly if the target was presented in the right side of the visual field, which is processed by the left hemisphere of the brain. For babies, the pattern reversed: they were quicker if the target was in the left visual field, which is processed by the right hemisphere. The results are published in Proceedings of the National Academy of Sciences1.
“The obvious conclusion is that language is constraining colour perception,” says Kay. Language certainly seems a good candidate reason for the difference, says Jonathan Winawer, who studies colour perception and language at Stanford University in California. But this is still a controversial idea, he adds, and not the only possible explanation. “There are other things that separate adults from infants,” he points out.
The conclusion fits in with another report co-authored by Kay, working with a different team, in the same issue of Proceedings of the National Academy of Sciences2. Using functional magnetic resonance imaging, he and colleagues from the University of Hong Kong and Queen Mary Hospital, also in Hong Kong, looked at which brain areas are activated when people make judgements about different colours.
When subjects viewed various coloured squares, samples that were easy to name in their local language (red and green, for example) provoked stronger activation in areas of the brain related to word-finding than hues that are harder to name (such as pinky-beige or greeny-blue).
Kay argues that this is because language is an integral part of the colour-perception process. The study is good indirect evidence for this, Winawer agrees, but it doesn’t show directly that language is affecting perception, he says. One might expect stronger activation in language areas when the colours are hard to name and people struggle for the words, he notes.
There is a long history to thinking that language affects how we perceive the world. In the 1930s, linguist Benjamin Lee Whorf proposed that the language a person speaks affects the way he or she thinks. A horde of experiments have since confirmed that language can shape our perception (of colour among other things). But direct evidence of this effect from brain imaging is only just starting to emerge. Kay says his new work “gives comfort to the Whorfian ideas that language is intimately involved in the way we process the world”.
Mind over language
Other, more sophisticated processes have also been found to be influenced by language. In a recent study published in the journal Social Cognitive and Affective Neuroscience, Chiyoko Kobayashi of Cornell University in Ithaca, New York, and colleagues suggest that even a concept as complex as 'theory of mind' — a concept that involves understanding how other people think — is influenced by the language a person speaks.
Kobayashi studied bilingual subjects' ability to solve tasks involving this faculty — for example, reading a story and answering questions about what the characters involved think has happened. For example, if a marble is put in a jar while a character called Alice is present, and someone then removes the marble while Alice is out of the room, what would various characters in the story say about where Alice thinks the marble is?
When Japanese–English bilingual subjects solved tasks involving this faculty, different patterns of brain activation occurred depending on the language they were using3. Overall, there was greater activity when they solved tasks in Japanese than in English. "Japanese people use more nonverbal and indirect communication than Americans," says Kobayashi. This could be at the root of the difference.
Kay next wants to find out more about how colour perception switches from the right to the left hemisphere as children get older. He is also interested in finding out whether similar changes occur for perception of things other than colour.
Franklin, A. et al. Proc. Natl Acad. Sci. USA 105, 3221-3225 (2008).
Tan, L. H. et al. Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0800055105 (2008).
Kobayashi, C., Glover, G. H. & Temple, E. Soc. Cogn. Affect. Neurosci. 3, 62-70 (2008).
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Smith, K. Perception coloured by language. Nature (2008). https://doi.org/10.1038/news.2008.638