Red: The Colour Currency of Nature

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Katy Beinart
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The Colour Currency of Nature, an article by Nicholas Humphrey, was first published in Colour for Architecture, ed. Tom Porter and Byron Mikellides, pp. 95-98, Studio-Vista, London, 1976.

In the article, Humphrey explores why colour vision has evolved in nature, noting that colour vision in primates evolved in order to compete effectively with birds; "It is for that reason, I suspect, that the trichromatic colour vision of most primates (including humans) is in fact so similar to that, say, of a pigeon".

He argues that the advent of modern technology has brought with it a debasement of the colour currency, so that the indiscriminate choice of colours in relation to objects has become meaningless, dulling our biological response to it. “From the first moment that a baby is given a string of multi-coloured – but otherwise identical – beads to play with, she is unwittingly being taught to ignore colour as a signal.” He goes on to discuss the significance of the colour red in humans evolutionary involvement with colour.

“ I was first alerted to the peculiar psychological importance of red by some experiments not on humans but on rhesus monkeys. For some years I had been studying the visual preferences of monkeys, using the apparatus shown below. The monkey sits in a dark testing chamber with a screen at one end on to which one of two alternative slides can be projected. The monkey controls the presentation of the slides by pressing a button, each press producing one or the other slide in strict alternation: thus when he likes what he sees he must hold the button down, when he wants a change he must release and press again.

I examined “colour preference” in this situation by letting the monkeys choose between two plain fields of coloured light. All the monkeys that were tested showed strong and consistent preferences. When given a choice between, for instance, red and blue, they tended to spend three or four times as long with the blue as the red. Overall, the rank order of colours in order of preference was blue, green, yellow, orange, red. When each of the colours was separately paired with a “neutral” white field, red and orange stood out as strongly aversive, blue and green as mildly attractive. Direct observation of the monkeys in the testing situation indicated that they were considerably upset by the red light.

When I deliberately added to their stress by playing loud and unpleasant background noise throughout the test, the aversion to red light became even more extreme (contributor's note: not really surprising). Further experiments showed that they were reacting to the red light exactly as if it was inducing fear. This aversion to red light is not unique to rhesus monkeys. The same thing has been found with baboons and also, more surprisingly, with pigeons.”

He discusses experiments on colour preference in humans, which appear to be at odds with those in other primates, but that this may be more to do with social and cultural conditioning, and the methodological problem in asking “which do you like best?”, a question which depends on context and construction of language. He then describes evidence which demonstrates how, in a variety of contexts, red seems to have a very special significance for humans.

“(1) Large fields of red light induce physiological symptoms of emotional arousal – changes in heart rate, skin resistance and the electrical activity of the brain.

(2) In patients suffering from certain pathological disorders, for instance cerebellar palsy, these physiological effects become exaggerated – in cerebellar patients red light may cause intolerable distress, exacerbating the disorders of posture and movement, lowering pain thresholds and causing a general disruption of thought and skilled behaviour.5

(3) When the affective value of colours is measured by a technique, the “semantic differential”, which is far subtler than a simple preference test, people rate red as a “heavy”, “powerful”, “active”, “hot” colour.

(4) When the “apparent weight” of colours is measured directly by asking people to find the balance point between two discs of colour, red is consistently judged to be the heaviest.

(5) In the evolution of human languages, red is without exception the first colour word to enter the vocabulary – in a study of ninety-six languages Berlin and Kay found thirty in which the only colour word (apart from black and white) was red.

6) In the development of a child's language red again usually comes first, and when adults are asked simply to reel off colour words as fast as they can they show a very strong tendency to start with red.

(7) When colour vision is impaired by central brain lesions, red vision is most resistant to loss and quickest to recover.

These disparate facts all point the same way, to the conclusion that humans as a species find red both a uniquely impressive colour and at times a uniquely disturbing one. Why should it be so? What special place does the colour red have in nature's scheme of colour signals?”

He suggests that the explanation of red's psychological impact must be that red is by far the most common colour signal in nature, by virtue of the contrast it provides with other colours in nature, and because it happens to be the colour most readily available to animals for colouring their bodies because it is the colour of blood. However, the disturbing nature of red lies in its ambiguity..

“If red was always used as a warning signal there would be no problem. But it is not, it is used as often to attract as to repel. My guess is that its potential to disturb lies in this very ambiguity as a signal colour. Red toadstools, red ladybirds, red poppies are dangerous to eat, but red tomatoes, red strawberries, red apples are good. The open red mouth of an aggressive monkey is threatening, but the red bottom of a sexually receptive female is appealing. The flushed cheeks of a man or woman may indicate anger, but they may equally indicate pleasure.

Thus the colour red, of itself, can do no more than alert the viewer, preparing him to receive a potentially important message; the content of the message can he interpreted only when the context of the redness is defined. When red occurs in an unfamiliar context it becomes therefore a highly risky colour. The viewer is thrown into conflict as to what to do. All his instincts tell him to do something, but he has no means of knowing what that something ought to be.

No wonder that my monkeys, confronted by a bright red screen, became tense and panicky: the screen shouts at them “this is important”, but without a framework for interpretation they are unable to assess what the import is. And no wonder that human subjects in the artificial, contextless situation of a psychological laboratory may react in a similar way. A West African tribe, the Ndembu, state the dilemma explicitly, “red acts both for good and evil”. It all depends.”

Full text of article at:

Contributors note: before reading this article, I had read a book by Victor Turner, “Revelation and Divination in Ndembu Ritual” which describes a series of poison ordeals used to test members of the tribe. The synchronicity of these two articles and the connection with the toy car lead me to consider the psychological instinct of the boy in tasting the car; was he in fact testing an intuitive response to the colour red, one which through social and cultural conditioning we have learnt to distinguish, and thereby undergoing an unconscious form of poison ordeal?