A different vision

Equality for all human beings is a laudable ambition. In fact, it should not be an ambition it should just be a reality that we accept and then get on with things. At the same time it is facile to deny differences from one individual to the next and nowhere are those differences more graphic and keenly felt than between the sexes. Every modern woman and man stands at the end of a long line of evolutionary pressures that has selected the mix of genes, hormones and general biochemistry that makes a woman a woman and a man a man. While sharing many commonalities women and men are also fundamentally different even to the extent that we see the world differently, not just at the level of interpretation but at the level of our sight.

This has been established in a study done on women and men aged over 16, all of whom had 20/20 vision either naturally or when corrected by glasses or contact lenses.

When asked to describe colours that were displayed to them the experiment showed that men need a slightly longer wavelength of light to experience the same hue as women. Men were also not as easily able to distinguish between colours as women in the centre of the spectrum.

In another test the subjects were shown an image consisting of light and dark bars. When the light and dark bars were alternated the image appeared to flicker. By varying how rapidly the bars alternated and how close together they were the researchers found that at moderate rates of change observers lost the ability to differentiate when bars were close together but gained the ability to differentiate when they were further apart. This was the same for both sexes. When the image change became faster though, men were better able to resolve the changing images than women.

The reason for these fundamental differences in vision might be that in the visual cortex there are high concentrations of receptors for male hormones. Additionally, male hormones also control the development of neurons coming from the thalamus into the visual cortex during embryo development.

Exactly how these differences may have been chosen from an evolutionary perspective remains unclear but it is fairly certain that women and men do see the world in different ways at the neuronal level.

No wonder we can’t always see eye to eye.