In developing a theoretical approach involving pattern perception, the problem of the definition of a ’pattern* must

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be resolved. The problem central to any theory primarily concerned with cognitive aspects of pattern recognition, that is the problem of feature analysis and feature extraction (Parker & Moore, 1972, p.59) remains unsolved at the present time. The notion that there are within visual patterns sets of "objective features" which will be extracted by all human perceivers may not hold at the cognitive level. There are various clear physiologically defined specialised feature detectors in the visual system, involved in stereopsis, move­ ment, contour, line, depth etc... In a recent review article, Gross (1973) notes that the visual areas in the monkey brain have now been mapped in some detail, but above a particular level the perceptual process becomes primarily a complex cognitive one, which cannot be ’mapped* physiologically.

It appears to be the case that the specialised sensory receptors of the visual system do provide a primary set of fundamental data forms on the basis of which the organism can analyse visual information input at a higher level, and that this primary sensory organisation is the same for all humans.

However, what differs between subjects is what the individual cognitive system elects to do with the information potentially available from these peripheral feature detectors. Whatever the particular ’significant* features of a visual information array which are selected and used in perception might be, they may ultimately be a function of a particular individual form, or style, of cognitive processing strategy. The possibility must be acknowledged theoretically that these strategies may vary considerably between subjects, and within subjects.

A further difficulty is whether or not a visual

information pattern may be arbitrarily defined, at some level, as a set of discrete "features", whatever these might be.

Visual information might well be encoded and stored in some analogue rather than digital form and, in spite of the existence of much computer-based research favouring digital processing, the possibility of full or partial analogue processing must at least be regarded as feasible until there is definitive research evidence either way*

These considerations raise critical problems for any theoretical model of perception and memory. The effectiveness and generality of the model at a cognitive level, must not be limited by, and dependent upon, the correctness or otherwise of certain assumptions concerning as yet unresolved questions about the nature of pattern recognition. If we cannot state unequivocally which 'features* of visual information input different subjects select as * significant *, nor whether these sets of features are continuous or discrete, nor what are the precise encoding, processing, storage and retrieval strategies involved, what can be truthfully and usefully said theoretically about this problem?

There is a solution to this theoretical dilemma. Consider a complex visual pattern which a subject first

memorises and unfailingly recognises on subsequent encounters. The picture or pattern can be defined simply as a quantity of information of some kind. Clearly it is at least this.

If we limit our definition to this very basic, but true statement, the theoretical difficulties raised by still

unresolved problems such as feature detection and analysis, the precise nature of the optic array, and the possibility of vast individual differences in processing, may be bypassed. It becomes possible to discuss patterns with some degree of generality.

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In order to recognise reliably the same visual array at any subsequent time, a subject must have processed and stored at least some proportion of this visual information, whatever that particular subject’s individual processing strategies might be, and however much it may be different from other subjects’ strategies*

It is emphasised that the concept of a ’quantity of information', as it is used in the present: context, does not refer to 'information* in the formal mathematical communication theory sense (Shannon and Weaver, 1949). As noted earlier (p.5), the application of these formal concepts to the complex cognitive problems of pattern perception and recognition has met with only limited success, and the ’irrational* way in which mathematical communication theory has been applied by many psychologists in the investigation of human performance has been strongly

criticised by Laming (1968, Ch. 1), for example. Garner (1962) points out that attempts to utilise formal information theory to determine an unequivocal constant maximum information- processing capacity for the human subject, in terms of ’bits’ of information, ha.ve not been successful. A large number of factors, such as instructional ’set’, overlearning of verbal material and of ballistic movement patterns, 'grouping* of responses, stiraulus-response compatability, and semantic properties of messages, are not amenable to arbitary quanti­ fication in terms of 'bits’ of information,

Broadbent (1971) states that the emphasis in this area of research has shifted from the deterministic approach of the investigators of the 1950's to the present probabalistic approach. The inapplicability of the formal mathematics of information theory to anything but the simplest situations has

resulted in the terra now being generally used in a manner closer to its intuitive or everyday sense. Moray (1967), Welford

(1968) and Broadbent (1971) use the term 'information' more in a conceptual, non-specific sense than purely as a term of

measurement. The present use is close to the term 'information' as it refers to computer programming, (i.e. the general processes of manipulation, rather than measurement of information).

Although the broad concepts of the "information sciences" (Neisser, 1967, p.7), which include formal communication theory, systems analysis and computer programming, have been of the

utmost significance and usefulness to modern cognitive psychology, Neisser argues that "the upshot of more than a decade of research is that information measures have little or no direct relevance to performance in most cases" (ibid. p.112).

In the present thesis, then, in the absence of any suitable objective metric to quantify precisely complex

perceptual information, the concept of a pattern as a 'quantity of information* is employed without reference to systems of units. As stated earlier, because it is a fact that patterns may be remembered (i.e. that information from the pattern is processed), we may speak meaningfully about the'total information content of a pattern' as a hypothetical quantity which may

include semantic aspects, and, although we cannot as yet

'measure' this in terms of some arbitary scaling system, we may clearly speak about proportions of this total quantity of

information.

It may be that different patterns represent different absolute quantities of some form of total pattern information, and that the same pattern may represent different quantities of information to different subjects. However, because the

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present concern is only with proportions of total information, which does not involve units of measurement, it becomes possible to consider information processing performance referent to

different complex patterns, and to different subjects, in a manner which facilitates direct comparisons on the basis of this common factor.

Consequently, when patterns are defined in this way it is proposed that the common factor linking similar subject performances may be considered purely in terms of proportions of pattern information utilised in various similar circumstances. In the following discussion, the notion of a 'pattern* is

CHAPTER II

The following chapter summarises and extends the basic theoretical ideas outlined and developed in Chapter I.

2.1 In familiar environmental contexts where the probability