Neural Networks. Vol. 6, pp. 147-149, 1993 0893-6080/93 $6.00 + .00 Printed in the USA. All rights reserved. Copyright © 1993 Pergamon Press Ltd.

BOOK REVIEW

Cognitive Psychology: A Neural Network Approach By Colin Martindale, Brooks/Cole Publishing Com-

pany, Pacific Grove, CA: 1991,282 pp. ISBN 0-534- 14130-7.

In the Preface, the author states that "Cognitive Psychology: A Neural Network Approach is an introductory level textbook that covers the basic topics and findings of cognitive psychology in a new and exciting way." Martindale's two goals are to give a qualitative coverage of the theory and usage of neural net- works and to present the field of cognitive psychology from a neural network point of view. The book is, in fact, the first attempt to describe the field of cognitive psychology from entirely within a neural network framework and for that rea- son alone is of interest.

The text is in general quite enjoyable to read and Martin- dale's chatty style is refreshing in a textbook. His qualitative discussion of neural networks is often quite good; he even makes a stab at a verbal description of some of the basic differential equations of neural network theory. The newcomer to neural networks, particularly if he or she already has some knowledge of cognitive psychology, will find the book an en- lightening introduction.

As a textbook in cognitive psychology, however, the book has many shortcomings. Although Martindale covers most of the important subareas of cognitive psychology, the discussion generally lacks the depth of some of the more standard texts in the field, such as John Anderson's Cognitive Psychology and Its Implications. One weakness that would be apparent to those with a background in traditional cognitive psychology is the dearth of data in the book. Psychology is at its heart an empirical science, and a presentation of some of the tech- niques and data of the classic studies should be a central part of any introduction to the field. Martindale generally discusses experimental results in a qualitative way. The first actual data do not appear until page 61, a quarter of the way through the book, and then only in the text. Furthermore, although Mar- tindale makes excellent use of illustrations and graphical rep- resentations, generally, the first graph of data does not appear until page 105.

The text is cohesive though, not just a hodgepodge of dif- ferent networks, one for each phenomenon to be explained. Martindale introduces some general principles and assump- tions early on and sticks with them throughout the text. He generally succeeds in making his case that a few basic neural network principals can go a long way towards aiding our un- derstanding of human cognition. The author draws heavily on the theories of Konorski, Grossberg, and his own work, though the ideas of Grossberg seem to be most key throughout.

All in all, Cognitive Psychology: A Neural Network Ap- proach is well worth browsing for the student or research psychologist who has not had a previous introduction to the neural network point of view and is particularly worthwhile

for those without training in mathematics. The book cannot be recommended as a stand alone textbook for a cognitive psychology course, however, but could serve nicely as a sup- plement to a basic introductory course in connectionism for psychologists.

A brief summary of the chapters of the book and assorted comments follow.

Chapter !: "Introduction". Amidst a somewhat cursory historical summary, Martindale starts off with two nice ex- amples, Collins and Quillian's (1969) spreading activation model of semantic memory, and a brief comparison of be- haviorist, information-processing, and connectionist descrip- tions of conditioning. These examples give some starting in- tuitions about the strengths of the connectionist approach.

Throughout the chapter, the author compares and contrasts the neural network approach and the by now classical infor- mation-processing approach. He diplomatically concludes that both approaches are useful, with the neural network approach perhaps being more precise when explaining relatively simple phenomena, and the information-processing approach being more useful for understanding more complex processes with- out getting bogged down in unnecessary details.

Chapter 2: "Pattern Recognition". This chapter introduces two topics that are important to the viewpoint built up in the rest of the book: The mechanism of lateral inhibition and the notion of hierarchical organization in cognitive systems (ex- emplified by Selfridge's, 1959, Pandemonium model).

The chapter also discusses Hubel and Wiesel's (1965) model of the visual system.

Chapter 3: "Mental Modules and Mental Contents". This the chapter in which Martindale first lays out in full the struc- ture which will be used to explain cognitive functioning throughout the rest of the book. Cognitive modules are defined as substructures in which excitatory connections join the nodes vertically and inhibitory connections join the nodes horizontally. For instructional purposes, Martindale makes the oversimplification that individual nodes or units can rep- resent entire concepts or objects. Vertical feedforward con- nections are assumed to be in the direction of increasing gen- erality (for example, nodes representing parts would feed- forward to nodes representing wholes). The idea is that such modules are repeated throughout the cognitive structure, with the specific function of each submodule resulting from its position in the network and the strengths of its connections. Martindale discusses a general sequence of these modules or analyzers: transduction (input), sensory analyzers, perceptual analyzers, conceptual analyzers (including semantic, episodic, and action systems), and finally, the motor response system (output).

Martindale also raises the questionable notion (first in- troduced up front in Chapter 1 ) that "consciousness corre- sponds to the set of cognitive units in sensory, perceptual, and conceptual analyzers that are activated above some threshold at any given moment.'" While the urge to explain

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consciousness is certainly understandable, such speculation (which is repeated throughout the text) detracts from the more important program of providing a connectionist frame- work for examining cognitive mechanisms.

Chapter 4: "'The Structure and Dynamics of Neural Net- works". Chapter Four nicely builds on the discussion of the previous chapter with a well-written introduction to Gross- berg's (e.g., 1980) notions of adaptive resonance and gated dipoles. Martindale uses resonance between word units and the letter units which connect to them to explain the word superiority effect, the fact that letters are recognized more accurately when they are presented within a word than when they are presented alone.

Following Grossberg, he also argues that lateral inhibition is not only useful for producing contrast enhancement in low- level vision, but serves as a general noise suppression mech- anism as well.

Chapter 5: "'Attention". Of course, what is "signal" and what is "noise" is relative to an organism's current motiva- tional state. Lateral inhibition is the natural mechanism for selecting the current focus of attention (following Walley & Weiden, 1973 ). The currently most activated node would be considered the focus of attention, while slightly less activated nodes would constitute the contents of short-term memory.

The arguments in this chapter are nicely summarized in the author's own words:

Sokolov's (1963) theory of involuntary a t t en t ion . . , holds that in- coming stimuli are compared to preexisting cortical models. If stimuli match these models, nothing more than normal perception results. lfa mismatch occurs, the arousal system is disinhibited and arouses the cortex. Orientation and attention result, and a new cortical model is constructed. Walley and Weiden argue that cognitive units "'select" themselves for attention by laterally inhibiting surrounding units. Cognitive units are aided in this processes by nonspecific inputs from the arousal system. Where attention is caused by mismatches between expectation and reality, Grossberg argues that inputs from the arousal system constitute a reset wave (p. 117).

Chapter 6: "'Primary Memory". Martindale borrows the term "primary memory" from James (1890) to refer to im- mediate sensory memory and short-term or working memory. From the information-processing point of view, it is typical to consider short-term and long-term stores to be separate modules or "places," whereas in a neural network, memory is simply a pattern of connections between nodes, and short- term memory becomes those nodes which are most active at any given moment (with the most strongly activated node occupying the focus of attention).

Lateral inhibition is the workhorse in this chapter, being applied to such diverse memory phenomena as the suffix effect (recall for the last item in a list is hampered if an additional, irrelevant item is tacked onto the end of the list), the primacy and recency effects in recall, and the von Restorffeffect (the item that is least like other items on a list is most likely to be recalled). The author also gives an alternative interpretation of the data from Sternberg's (1966) classic study. Sternberg found that the time to verify or reject a target digit as having appeared in a list ofdigits was a linear function of the number of digits in the memory set. Sternberg reasoned that subjects were searching serially (and exhaustively) through the mem- ory set to find the target. Martindale discusses the possibility

that the overall increase in lateral inhibition resulting when the memory set size increases could produce the results.

Chapter 7: "Learning and Forgetting". For the connec- tionist, to learn is to be conditioned and Martindale does a nice job of reviewing connectionist models of animal learning, explaining the standard phenomena of extinction, blocking, overshadowing. Although one may certainly raise the question of whether the principles of conditioning are adequate for understanding human learning and memory, the most sur- prising omission from the chapter is the failure to mention the standard connectionist learning algorithms such as back propagation.

Chapter 8: "Long-Term Memory". Martindale presents the three generally agreed-upon components of long-term in- formation storage: semantic memory (for facts), episodic memory ( for events ), and procedural memory ( for actions). Semantic memory is modelled as a hierarchical semantic net- work following Collins and Quillian (1969) and Collins and Loftus ( 1975 ). More specific nodes such as "'dog" and "cat'" feed into category nodes such as "mammal" and then "ani- mal." Martindale suggests that certain category priming effects are analogues of visual Mach bands (the result of lateral in- hibitory contrast enhancement) , if a semantic category is given, subjects" judgements about highly typical members of the category will be improved, but judgements about more atypical category members will be impaired. Martindale pre- sents the Test-Operate-Test-Exit (TOTE) model of Miller, Galanter, and Pribram (1960) as the basis of procedural memory. When there is a mismatch between the desires of the organism and the actual state of the organism, certain actions (built-in and /o r learned) are performed to reduce the difference. As discussed in Chapter 5, such mismatches also lead to arousal and attention.

Chapter 9: "Language". This is probably the chapter in which connectionist principles are mentioned the least. It provides a very brief overview of many aspects of human linguistics and psycholinguistics: phonology, syntax, seman- tics, aphasia, and development.

Chapter 10: "'Thinking". A number of important topics are covered in this chapter with the catch-all title: deductive and inductive reasoning, problem solving, creativity, and de- cision making. Although the coverage is brief and straight- forward, a couple of interesting suggestions regarding neural networks are made. Martindale suggests that creativity may be at least in part the result ofone's ability to defocus attention, that is, to increase the number of cognitive units which are active in short-term memory. He also uses lateral inhibition to explain Tversky's ( 1977 ) observation of context effects in similarity judgements: The apparent similarity of item A to item B will decrease if an item C, which is more similar to B than to A, is brought into the situation. The idea is that similarity is judged according to how much the nodes rep- resenting items inhibit one another, with the assumption that more similar nodes inhibit each other more strongly. So the new item C inhibits item B, in turn preventing B from in- hibiting item A as strongly as it did initially.

Vincent Brown The Universit), of Texas

Department of Ps)'cholog), 3rlington. TX 76013-0528

Book Review 149

REFERENCES

Anderson, J. R. (1990). Cognitive psychology and its implications (3rd ed.). New York: Freeman.

Collins, A. M., & Loftus, E. E ( 1975 ). A spreading activation theory of semantic processing. Psychological Review, 82, 407-428.

Collins, A. M., & Quillian, M. R. ( 1969 ). Retrieval time from semantic memory. Journal of l'erbal Learning and l,brbal Behavior. 8, 240- 247.

Grossberg, S. (1980). How does a brain build a cognitive code? Psy- cholt~gical Revie~t: 87, I-5 I.

Hubel, D. H., & Wiesel, 1". N. ( 1965 ). Receptive fields and functional architecture in two non-striate visual areas ( 18 and 19 ) of the cat. Journal of Neurophysioh~.~: 28, 229-289.

James, W. (1890). The principles ofps)z'hology New York: Holt, Ri- nehart, & Winston.

Miller. G. A., Galanter, E., & Pribram, K. H. (1960). Plans and tile structure of behavior. New York: Holt, Rinehart, & Winston.

Selfridge, O. G. (1959). Pandemonium: A paradigm for learning. In D. V. Blake & A. M. Uttley (Eds.), Proceedings of the symposium on the mechanization of thought processes" (pp. 511-529). London: H. M. Stationery Ot~ce.

Sokolov, E. N. (I 963 ). Perception and the conditioned re./le~. New York: MacMillan.

Sternberg, S. (1966). High-speed scanning in human memory. Science, 153, 652-654.

Tversky. A. ( 1977 ). Features of similarity. Psychological Revie~t: 84, 327-352.

Walley, R. E.. & Weiden, T. D. (1973). Lateral inhibition and cognitive masking: A neuropsychological theory of attention. Psychological Rea,ie~: 80, 284-302.