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Images of mind


In memory of Donald Broadbent and Allen Newell


John Fox

Advanced Computation Laboratory

Cancer Research UK

44 Lincoln's Inn Fields

London WC2A 3PX

Email john.fox@cancer.org.uk

Telephone +44 (0) 20 7269 3624

Fax +44 (0) 20 7269 3186

Images of mind


In memory of Donald Broadbent and Allen Newell

Abstract


The idea of “mind” did not spring fully formed into human consciousness. On the contrary it has been articulated slowly through the millennia, drawing upon countless metaphors and images in different cultures at different times. In the last 50 years the concepts of conventional science and technology have provided the primary images that we employ in discussion of mental processes, though there are presently many competing perspectives. Every one of these images is incomplete when it comes to explaining mental phenomena, and many are inconsistent. In this chapter we review a few of the prominent perspectives that have influenced cognitive science in the last half century or so, from information processing psychology to AI, and conclude that a unified theory of mind will need insights from multiple viewpoints. The challenge to the field is to avoid disputes over different positions and look for ways of bringing them together.

Keywords: Agents, AI, cognitive systems, knowledge representation, cognitive modelling, mental states, cognitive theory.

Introduction


"The various properties that distinguish Mind from what is not Mind are summed up in three great general properties, named Emotion or Feeling, Volition or Will, and Intellect or Thought."

Chambers' Information, 1884.

It is not clear when the idea of "mind" emerged. It appears that early mentalistic terms appeared in ancient Hebrew. These were originally used to refer to physical body parts but gradually acquired additional associations. For example, the most primitive meaning of the Hebrew word nepesh was throat or gullet, which came to be associated with the wish for food and drink, later a more general notion of "life force" and in due course it came to refer to the self. Similarly the word ruach initially refers to breath or the organ of breathing and later the power or force behind the breath, and hence motivating power. Finally, leb refers to the heart. The notion of the heart as the seat of human emotions emerged gradually from that of the heart as the chest or bosom but according to MacDonald (2003) came to function in all aspects of human existence (emotional, cognitive and volitional) and its most important Hebrew usage is "in passages that clearly indicate intellectual, cognitive and reflective operations".


Greek learning was notable for the systematisation of knowledge, with the development of technical disciplines like arithmetic, geometry, astronomy, music, optics, medicine, logic and politics. Psychological thinking, however, does not appear to have developed far but Aristotle and Plato made a start. Aristotle had begun to try to understand the "intellect" with such distinctions as the passive intellect, which “receives intelligible species”, and the agent intellect which “produces intelligible objects”; notions that are only just intelligible to the modern reader. Plato and other Greek thinkers expressed other intuitions, some of which we can still find in contemporary "folk" psychology though there were strong dissonances as well. For example, “one of Plato's main ideas was that the rational soul (i.e. mind) is immortal, which is not congruent with a modern, materialist point-of-view”1. Generally it seems that these early writers were struggling to understand mental phenomena, as we still do today.

One obvious reason for the difficulties faced by early thinkers in understanding mind in anything like modern terms was the existence of competing philosophical modes of enquiry and ideologies. Religion, and attempts to explain all existence with religious ideas, strikes the secular scientific investigator as an obvious source of confusion. Distinctions between mind as a cognitive entity and mind as coextensive with "soul" were constantly blurred. Christian thought appears to have embodied a curiosity about the subjective experience of cognition, but could not shake off the need to ensure its consistency with religious doctrine. By the 9th century Islamic scholars had greatly developed the Aristotelian and other earlier systems and developed a differentiated view of cognition that distinguished perceptual, epistemic, rational, intentional, ethical and other aspects of the intellect. However this was all set within a framework bounded by the unknowable mind of God (as in Afarabi's model of mind shown in figure 1, reproduced with permission from MacDonald 2003).




Figure 1. An Islamic view of the intellect (from MacDonald, 2003)

The separation of questions to do with the nature of rational mind and more mystical ideas was probably incremental, though we tend to see history in terms of sudden lurches toward modern ideas in “periods” such as the Renaissance and the Enlightenment. At any rate by the nineteenth century philosophical and introspective enquiry had acquired a fairly clear, if intuitive, idea of mind, which could be summarised in terms of a small number of basic ideas, as illustrated by the quote from Chambers Encyclopaedia above.

By this time philosophical introspection was also beginning to give way to more modern methods of investigation of mental phenomena, for example see (Solso, 1998) for a historical review, and by the 20th century a number of scientific methodologies had been established. The medical and physiological tradition sought explanations of mind in the structure of the brain and neural apparatus, for example, though the psychoanalytic traditions were more concerned with experience than physical mechanisms, explaining mental phenomena in terms of abiding human preoccupations and culture-specific metaphors. Behaviourism investigated human and animal behaviour in the laboratory without invoking mentalistic ideas at all.

These and other streams of thought played out over the first half of the 20th century and by the middle of the century most scientists took it for granted that brains implement minds, that the best way of studying this relationship was through laboratory experiment and the development and testing of mechanistic models of structure, function and behaviour. This is the starting point for the present chapter, the purpose of which is to bring together a number of contemporary paradigms that spring from there.


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