Nicholas Humphrey

Vision in a Monkey without Striate Cortex: A Case Study

A rhesus monkey, Helen, from whom the striate cortex was almost totally removed, was studied intensively over a period of 8 years. During this time she regained an effective, though limited, degree of visually guided behaviour. The evidence suggests that while Helen suffered a permanent loss of ‘focal vision’ she retained (initially unexpressed) the capacity for ‘ambient vision’.

Species and individuals in the perceptual world of monkeys

When a monkey is given the choice of looking at a novel picture or a blank white screen he shows an initial preference for the picture which usually abates within about 200 seconds; if the picture is then changed for another his preference revives. The level of preference for the second picture depends on the degree to which it is perceived as ‘similar’ to or ‘different’ from the first. This technique has been used to investigate how rhesus monkeys classify pictures of animals, and in particular the extent to which they differentiate between individual animals of the same species. Two classes of animal pictures were used, namely pictures of other rhesus monkeys and pictures of domestic animals. The results indicate that inexperienced monkeys, to whom the domestic animals are unfamiliar, treat individual domestic animals of the same species as being closely similar; they treat individual monkeys, on the other hand, as being quite different from each other. Experienced monkeys, however, who have been exposed over the course of 6 months to many further pictures of animals, come to treat all individuals as different from each other, so that one pig, say, is now seen as being as different from another pig as is one monkey from another.

'Interest' and 'pleasure': two determinants of a monkey's visual preferences

When given a choice between two visual stimuli (plain fields of light of different colour, photographs, cine films, etc.) monkeys show strong and consistent preferences. The strength and direction of the preferences is determined by two independent factors: the monkeys relative ‘interest’ in the stimuli (determined largely by their information content) and his relative ‘pleasure’ (determined by qualities such as colour and brightness). With an unchanging stimulus ‘interest’ rapidly fades but ‘pleasure’ (or ‘unpleasure’) remains stable. If the two factors are set against each other, as when a red-coloured cine film is paired with a plain white field (the pictorial content of the film being interesting, its colour unpleasant), interest over-rides pleasure in determining the observed preference. A quantitative model based on these principles predicts the behaviour in a variety of situations with great accuracy.

Do Monkeys' Subjective Clocks Run Faster in Red Light than in Blue?

When monkeys are given control of the illumination in a testing chamber, it has been found, under three conditions, that they spend less time with red light than with blue. But the results cannot easily be explained in terms of ‘preference’. Rather, the results suggest that monkeys judge ‘subjective time’ to pass nearly twice as fast in red light as in blue.

Dreaming as play

Dreaming can provide a marvelous opportunity for the “playful” exploration of dramatic events. But the chance to learn to deal with danger is only a small part of it. More important is the chance to discover what it is like to be the subject of strange but humanly significant mental states.

The lure of death: suicide and human evolution

At some point in evolutionary history, human beings came to understand, as no non-human animals do, that death brings to an end a persons bodily and mental presence in the world. A potentially devastating consequence was that individuals, seeking to escape physical or mental pain, might choose to kill themselves. This article is part of the theme issue ‘Evolutionary thanatology: impacts of the dead on the living in humans and other animals’.

Effects of red light and loud noise on the rate at which monkeys sample the sensory environment.

Monkeys, given the opportunity to move between two featureless chambers, ‘sample’ first one, then the other in a way which reflects a Poisson decision process. The rate of sampling is higher in red light than in blue and in loud noise than in quietness. We suggest that monkeys ‘tune’ their sampling rate to the a priori probability of change in the environment.

‘This chimp will kick your ass at memory games – but how the hell does he do it?’

Extraordinary evidence generates extraordinary claims. I discuss the remarkable memory skills of chimpanzees tested in the Kyoto Primate Laboratory, and suggest a novel – but deflationary – hypothesis to explain them. Could the chimpanzees, who have been highly trained to learn the sequence of Arabic numerals, have developed number–colour synaesthesia?

The invention of consciousness

In English we use the word “invention” in two ways. First, to mean a new device or process developed by experimentation, and designed to fulfill a practical goal. Second, to mean a mental fabrication, especially a falsehood, designed to please or persuade. In this paper I argue that human consciousness is an invention in both respects. First, it is a cognitive faculty, evolved by natural selection, designed to help us make sense of ourselves and our surroundings. But then, second, it is a fantasy, conjured up by the brain, designed to change the value we place on our existence.

Person as moral scientist

Scientists are generally more moral, and moralists more scientific, than Knobe suggests. His own experiments show that people, rather than making unscientific judgements about the moral intentions of others, are behaving as good Bayesians who take account of prior knowledge.