Earlier this week we covered research reported as showing “Women prefer pink” and some of the criticism it received. Anya Hurlbert, a neuroscientist at Newcastle University and one of the authors behind the research, has been kind enough to send us a response to her critics.
Click through for the full (unedited) response.
A note on the cost of this research. Our study was an off-shoot of our basic research into colour perception, which we pursue in order to gain a better understanding of how the human brain works. There was effectively no cost to it. Apart from the specific findings themselves (the hue preference patterns), there is a practical benefit in the demonstration of an objective, replicable test for colour preference, which yields quantitative descriptors of preference for individuals and groups. The numerical weights on the two preference components are independent of language; therefore the test lends itself to application in other cultures and other domains. Future studies may readily seek correlations between the simple set of weights and other factors (for example, other features of the stimuli or other characteristics of the observer), which might help to explain fundamental aspects of colour perception. For example, how is colour represented in visual memory? Why and how (in terms of the neural mechanisms) does colour evoke strong preferences or emotional reactions?
Hurlbert also found that Chinese participants in the trial had a slightly stronger preference for red shades than the British, which she suggests may be because in China red is the colour of good luck.
A clarifying note on the cultural difference. In their preference patterns, Chinese females had a more pronounced shift towards “reddish” contrasts than UK females (see note on terminology below). Like the UK males, Chinese males preferred “greenish” contrasts – just not as much as the UK males. So, although red is the colour of good luck for both sexes in China, there is still a sex difference in the ‘red-green’ dimension of colour preference, and this difference is in the same direction as for the UK population.
Terminology. Part of the difficulty in popularising colour vision research lies in translating specific technical terminology into everyday language. Colour names such as “red” and “pink” are meaningful to everyone, but not in a consistent, reproducible way. Colour names are imprecise labels, not quantitative descriptors of colours. Here when I say “reddish” I mean “positive on the ‘red-green’ colour-opponent dimension of colour encoding in the visual system”. This ‘red-green’ dimension is a fundamental stage of colour vision, in which the response of the middle-wavelength-selective receptor (in shorthand, the ‘green’ receptor) is subtracted from the response of the long-wavelength-selective receptor (the ‘red’ receptor). The endpoints of this dimension do not correspond perfectly to what we name “red” or “green”, but are close – the relationship between neural mechanisms and perception is an important area of research.
Furthermore, the colour you see at one location is also influenced by the colours at surrounding locations – or, to be precise, the colour you see is determined not just by the local stimulation of your ‘red’, ‘green’ and blue’ receptors, but by how much that contrasts with the stimulation from the background. When I say “reddish” contrast, I mean that the colour stimulates the ‘red-green’ dimension more positively than its background does. A colour may have a “reddish” contrast with the background without generally being named “red”. For example, a yellow banana against a green background has a “reddish” contrast. Our results showed that the female pattern of hue preference is both more pronounced and shifted towards the “reddish” end of the red-green dimension, in comparison with males. When forced to choose between two colours neither of which they would have named “red”, females tended to choose the one that had a larger “reddish” contrast. Males tended to choose the one with the smaller “reddish” contrast. Both males and females tended to choose the one with the larger “bluish” contrast – i.e. the one that activated the ‘blue-yellow’ dimension most in comparison with the background. It happens that many of the colours we name “pink” have a high “bluish” contrast and a high “reddish” contrast – hence, a preference for “pink” may result from these basic tendencies.
But in the tropical zones where humans originated ripe fruit would be yellow (banana), orange (the eponymous orange), green (custard/Chinese apples), black/purple (many sorts of berries) and actually many other colours. Red is usually accepted to be a sign of danger in foods because more species of poisonous berries are red compared to other colours.
As I said above, a yellow banana against a green background has a “reddish” contrast. There is strong evidence supporting the notion that the ‘red-green’ dimension of colour vision evolved to optimise fruit-finding amongst foliage, some 30-40 million years ago. The colours of fruit that primates actually pick and eat have been measured in French Guiana, for example, and analysis demonstrates that many of their colours have “reddish” contrasts against their leafy background, which match the contrasts that the primates’ particular ‘red-green’ dimension is best able to discriminate. See Regan et al. in Phil. Trans. Roy. Soc. London B (2001; vol 356, pp 229-283), “Fruits, foliage and the evolution of primate colour vision” for a comprehensive review and empirical study.