The general acceptance of Darwin's theory of evolution by natural selection made animal psychology an important area of research. If human limbs and organs have their parallels in animals, and their development can be traced through our animal ancestors, so also the conscious mind must have evolved. But it is not that simple, as Euan Macphail demonstrates in this accessible discussion of the subject.
Macphail distinguishes between "self-consciousness" (concerned with knowledge) and "feeling consciousness". He says that a complete account of human consciousness would include both, but he regards feeling consciousness as the more fundamental, and the one that most people would attribute to at least some animals. Among the different aspects of feeling,Macphail treats the ability to experience pain and pleasure as the most basic: "If we cannot convince ourselves that an organism experiences pleasure or pain, then we should assume that it has no experience." He considers that most of us do regard animals as capable of feeling pain, on the basis of their behaviour. If an animal is subjected to treatment that would cause pain in a human, and behaves in a similar way to a human in pain, then we conclude that the animal is in pain. Such a conclusion, he claims, is not valid, since none of the behaviours can be identified with pain. Any of them could be carried out by an actor without the experience of pain.
If animals cannot be shown to have conscious experience, that might cast doubt on the idea that human consciousness evolved. Such doubts are reinforced when we consider the function of consciousness. A commonsense view is that conscious awareness of pain developed to protect an organism from harm by encouraging avoiding action. On the other hand, a sense of pleasure would attract it to beneficial situations. Unfortunately this is not the case. A reflex reaction would be much faster and therefore more effective than a response that involved feeling pain and then making the conscious decision to react.
More question marks against the practical necessity for conscious experience are provided by various experimenters. For instance, "blindsighted" patients have intact eyes but suffer damage to the area of the brain thought to process visual information. They report being unable to see, but when asked to guess what they would see if they could see, they get the correct answer at a rate well above chance. This and other examples of "non-conscious awareness" remove one of the most likely functions of consciousness: information gathering and processing.
Macphail concludes from the lack of an obvious function for consciousness that it is neither necessary nor indeed possible to account for the evolution of consciousness by natural selection. Since it cannot be proved that any non-human organism is conscious, he seeks the key to understanding how consciousness arose in something that is uniquely human: language.
At the beginning of the book he says it is "obvious" that "the fact that only humans talk is in itself no reason to suppose that only humans are conscious", but in his discussion of experimental and theoretical research he moves inexorably towards the view that language does create conscious experience. He agrees with Noam Chomsky that humans have an innate language competence, and he suggests that this might be the basis of the concept of self that infants develop.
In the closing pages, Macphail speculates "that a self is a prerequisite of any conscious experience", and therefore, by a series of backward steps,so is language. He is aware that this might lead to unwelcome implications, such as justifying the maltreatment of animals and infants on the grounds that they do not feel. It would be a shame if such fears prevented this sensitive book from being taken seriously.
Revd Anthony Freeman is managing editor, Journal of Consciousness Studies .
The Evolution of Consciousness
Author - E. M. Macphail
ISBN - 0 19 851324 5
Publisher - Oxford University Press
Price - £15.99
Pages - 256