Which side of your brain processes faces?

You may have read that the left hemisphere of the brain is better at language. So what is the right hemisphere good at?


The history:

It is part of folklore that the left side of a person's face (the side on the viewer's left) looks more like the person than the right. Wolff (1933) thought argued that people expressed their personality more on that side of their face. Gilbert and Bakan (1973), however, demonstrated that the bias was due to the perceptual system.


What you saw:

In the experiment you were presented with pairs of images like the two below. Try and remember which one of this pair you thought was more masculine (top or bottom). The face images are computer generated 'chimearas' , that have some interesting properties.


Try looking just at the left half of the faces by moving your mouse over this text.
You can see that the top face looks feminine and the bottom face masculine.

To get back to the original images move your mouse over over this text.


Now try looking just at the right side of the images move your mouse over over this text. Now you can see that the top face looks masculine and the bottom face feminine.


If in the test you thought that the top face was more feminine then you were using information on the left side of the images. (Most of the time people use the information on the left side.)

If you saw the lower face as more feminine you we using information on the right side of the image.

So both of the images are half male and half female. The bottom image is a mirror image of the top and therefore both are equally masculine and equally feminine. Only the perceptual system thinks they are different.Why do the images look different?

In the experiment that you have just performed most people base their judgements on the information in the left side of the image rather than the information on the right.The visual system is wired so that the left side of vision goes to the right side of the brain (and information from the right side of vision goes to the left side of the brain). Thus the information 'emitted' from the left side of a face goes directly to the right side of your brain. Our experiment indicates that most people use their right brain to judge the sex, expression, age and atrtractivness of faces. Why this is, isn't known, although it may be due to the right brain being better at processing configuration.Why does the experiment not always work? One reason is that some people process faces equally on both sides of their brain.



Further information:

Here is a paper of mine in Adobie PDF format:

Burt, D. M., & Perrett, D. I. (1997). Perceptual asymmetries in judgements of facial attractiveness, age, gender, speech and expression. Neuropsychologia, 35, 685-693.

Images and text Copyright 2000, The Perception Lab, University of St Andrews

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