Wednesday, January 04, 2006

Language helps vision

There is no doubt that there are hemispheric differences in the brain. We know that in most people, the left hemisphere is dominant for language production. Damage to the left lateral prefrontal cortex produces the well-known expressive aphasia. On the other hand, language comprehension is seen to involve both hemisphere, or at least that the hemispheric asymmetry is lower.

So much for language. But does language influence the way we perceive things? According to the old Sapir-Whorf hypothesis there is a systematic relationship between the grammatical language a person speaks and how that person both understands the world and behaves in it. In other words, language influences thought. But does language influence "direct" perception as well?

In a recent study in PNAS, Gilbert and colleagues from the Ivry Lab demonstrate that language may play a role in perception. Below is a quote from Nature with further link to the full version. The original article by Ivry can be found here.


The language-loving left hemisphere of the brain can spot different colours faster than it can identify different shades of the same colour.

Our perception of colours can depend on whether we view them from the left or the right, scientists have found. They say this demonstrates how language can alter the way we see the world.

The idea that language can affect cognition is not new. In the 1930s, the American linguist Benjamin Lee Whorf proposed the controversial hypothesis that the structure of language affects the way people think. Later studies have hinted that this may be true in some circumstances (see 'Tribes without names for numbers cannot count'). But whether language affects our perception of the world has remained an open question.

Richard Ivry of the University of California, Berkeley, and colleagues suspected that separating out the effects of visual input to the right and left brain hemispheres might yield some clues. Language is processed mainly in the left hemisphere of the brain, which also deals with signals from the left side of the retinas in both our eyes.

Because light from objects to our right falls mainly into the left-hand area of our retinas, the researchers hypothesized that colours to the right would feel the influence of language more keenly. Conversely, objects on our left side activate the right hemisphere of the brain, so the effect of language would be minimal.

Full Text at Nature


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