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Cognition through color
Book reviews
Jules Davidoff, Cognition Cambridge, MA, 1991.
through Color. A Bradford
291
Book, The MIT Press,
The first chapter, which I reread after previously reading the whole book, gives a good summary of the author’s message. The problem is only that you better read this chapter after reading all the other chapters. The book deals in not too many pages with a huge number of fundamental problems. I had to read the book twice in order to estimate the reach of it. Although the author states that he is mainly describing the work of others, he very often gives his personal view on those papers instead of just reporting the work. This makes the reading much more interesting, because the author looks at the literature from his particular point of view which gradually emerges during the book. The book as a whole is impressive, but hard to judge for somebody who is not an expert in all the fields Davidoff is dealing with. The content of the book shifts from pure perception to pure cognition, giving the perceptual researcher the strong impression that he/she needs to know more about the very complex mixed perception/ cognition phenomena. The neurophysiological base of modularity described in chapter 2 gives important and wisely reduced schemes of retinocortical pathways and more importantly, the neurophysiological data are given with an interpretation by the author, not so much as data by others. At several places it is made clear that data get their meaning only in the light of the theory prevailing at that particular time. There are very striking examples of this kind in the book. Besides explanations of existing versions of ‘where and what system’, it is argued that with the present knowledge, at least 24 areas in the cortex are in some way involved in visual processes, deriving simple functions for areas differing in physiology and/or anatomy must rest on an ‘unashamedly reductionist’ basis. Davidoff presents us with a nice description of the change in aims in the neurophysiological research, from hierarchical ordering of information processing (culminating in the grandmother-cells) towards the concept of multiple parallel processes/ channels/ streams or whatever term might be fashionable. Apart from these metatheoretical considerations there is a systematic treatment of the several stations in the retinocortical pathways: retina, LGN, Area 17, the blobs and interblobs, area 18 and beyond that. To be clear: especially the processing of colour is considered. The information is presented in a concise way. Where possible a few tables are used for summarizing the main features. The ongoing discussion about magno and parvocellular layers in the LGN is discussed in extenso. The blobs in area 17 play a particular role for the processing of colour. Davidoff builds up evidence in favour of the existence of modular input channels on the one hand and in the same chapter also collects the counterevidence. In summary, the neurophysiology is not clear about the question whether there exists an independent
292
Book reciews
stream for colour processing. Davidoff’s own opinion about the status of the conclusions from neurophysiology can be found later in the book. He does not think that the conclusion of the existence of a really separate stream for colour is correct. Davidoff’s own specialization is neuropsychology, and in chapter 3 he amply goes into the existence of different forms of achromatopsia, because he claims that if achromatopsia exists in a pure form, i.e. completely absence of colour vision and not a single disturbance in other sensory functions, then it would be a very strong case for the existence of a separate colour module. The problem thus far is that if colour and form would be completely independent modules one would expect form perception without colour perception (which is easy to imagine) and the reverse (which is harder to imagine). Chapter 4 is concerned with a tool to measure colour modularity: the use of isoluminant stimuli. The great problem with this particular tool is that one agrees upon the findings that both motion and stereopsis and some other specific form processes do not show up too well under isoluminance. They are supposed to be colour blind. But there is also good evidence that the phenomena do not disappear completely, as the theory of independent streams would require. There is a still ongoing debate about the possible causes of residual effects: optical and perceptual artefacts. Chapter 5 deals with the formation of temporary representations; especially the formation of a pictorial register. The pictorial register is a follow up of the iconic memory. The content of chapter 5 portrays a gradual shift from the feature-model of Treisman to a domain-model for the relevant modular input organization. Although the chapter reads rather easily, it is not easy to reproduce what is maintained precisely. While it is clear that the pure model of Treisman is not applicable, it is not clear whether the domain-concept is much better either. The issue of attention is complicated enough to fill books by itself. Chapter 5 makes an attempt to condense the discussion in less than 15 pages. At the end of chapter 5 and in chapter 6 there is a gradual transition to the important distinction between boundaries and surfaces or more precisely, Davidoff shifts from the ‘Marr-like’ modular approach to a ‘Grossberg-like’ non-modular approach of object recognition. The heart of the attention reallocation is in the boundary segmentation process. This process does not require object knowledge, and this gives the author the opportunity to place important other activities (like naming etc.) outside this central process. Chapter 7 is concerned with object knowledge: ‘Entry level representations’ form an important element in Davidoffs approach. The entry level representation is a representation ‘which would require the least perceptual analysis to build a detailed representation’. Special attention is paid to the separate location of the colour description. It is not a part of the entry level representation. This entry level description only contains information about shape and
Book reviews
293
size, i.e. boundary information, no information about surface properties like texture and colour. I found it difficult to summarize this chapter, although it certainly contains a lot of information. An essential part of the model introduced by Davidoff in chapter 8 is the Internal color space, a kind of reference centre for the colour description. It contains the colour palette of the observer, i.e. the categories, to be distinguished from the names given to the colours. The internal colour space is not simply related to either the neurophysiology of colour vision, nor to the names used for the colours. Davidoff refers to old literature (Sittig 1921) to distinguish colour agnosia from agnosia for colour names. The internal colour space has a similar function for object colours as the entry level representation has for objects. This level is different from the colour naming stage. This difference is important for the distinction between Colour Agnosia and Colour Name Amnesia. An interesting side step in this chapter has to do with the relations between colours and emotions, which are much less well established than is often assumed. In the next chapter Davidoff offers more evidence for his viewpoint that colour does not play a role at the entry level representation. There are a few tables in which many neuropsychological studies on object and colour recognition disturbances are summarized. Chapter 11 deals with the important topic of colour naming in normals and in brain-injured subjects. It describes the relatively late development in children of the full spectrum of colour names. For me the term Colour stupidity (the authors writes ‘color stupidly’ as a translation of Farbendummheit) was completely new. A description of the Whorf hypothesis is given and a number of interesting experiments in colour naming is summarized, before an overview is given of disorders in colour naming. Cognition through Color is a nice book to read several times if only because of the very extensive literature review in the area of central colour disorders which is rather difficult to access. Ch.M.M. de Weert NICI, University of Nijmegen P.O. Box 9104 6500 HE Nijmegen The Netherlands
Michael W. Eysenck (ed.), Wiley, Chichester, 1990.
Cognitive Psychology: An International Review.
The title that is given to this collection of review chapters is a bit misleading. Although the book is concerned with cognitive psychology, it is
Jules Davidoff, Cognition Cambridge, MA, 1991.
through Color. A Bradford
291
Book, The MIT Press,
The first chapter, which I reread after previously reading the whole book, gives a good summary of the author’s message. The problem is only that you better read this chapter after reading all the other chapters. The book deals in not too many pages with a huge number of fundamental problems. I had to read the book twice in order to estimate the reach of it. Although the author states that he is mainly describing the work of others, he very often gives his personal view on those papers instead of just reporting the work. This makes the reading much more interesting, because the author looks at the literature from his particular point of view which gradually emerges during the book. The book as a whole is impressive, but hard to judge for somebody who is not an expert in all the fields Davidoff is dealing with. The content of the book shifts from pure perception to pure cognition, giving the perceptual researcher the strong impression that he/she needs to know more about the very complex mixed perception/ cognition phenomena. The neurophysiological base of modularity described in chapter 2 gives important and wisely reduced schemes of retinocortical pathways and more importantly, the neurophysiological data are given with an interpretation by the author, not so much as data by others. At several places it is made clear that data get their meaning only in the light of the theory prevailing at that particular time. There are very striking examples of this kind in the book. Besides explanations of existing versions of ‘where and what system’, it is argued that with the present knowledge, at least 24 areas in the cortex are in some way involved in visual processes, deriving simple functions for areas differing in physiology and/or anatomy must rest on an ‘unashamedly reductionist’ basis. Davidoff presents us with a nice description of the change in aims in the neurophysiological research, from hierarchical ordering of information processing (culminating in the grandmother-cells) towards the concept of multiple parallel processes/ channels/ streams or whatever term might be fashionable. Apart from these metatheoretical considerations there is a systematic treatment of the several stations in the retinocortical pathways: retina, LGN, Area 17, the blobs and interblobs, area 18 and beyond that. To be clear: especially the processing of colour is considered. The information is presented in a concise way. Where possible a few tables are used for summarizing the main features. The ongoing discussion about magno and parvocellular layers in the LGN is discussed in extenso. The blobs in area 17 play a particular role for the processing of colour. Davidoff builds up evidence in favour of the existence of modular input channels on the one hand and in the same chapter also collects the counterevidence. In summary, the neurophysiology is not clear about the question whether there exists an independent
292
Book reciews
stream for colour processing. Davidoff’s own opinion about the status of the conclusions from neurophysiology can be found later in the book. He does not think that the conclusion of the existence of a really separate stream for colour is correct. Davidoff’s own specialization is neuropsychology, and in chapter 3 he amply goes into the existence of different forms of achromatopsia, because he claims that if achromatopsia exists in a pure form, i.e. completely absence of colour vision and not a single disturbance in other sensory functions, then it would be a very strong case for the existence of a separate colour module. The problem thus far is that if colour and form would be completely independent modules one would expect form perception without colour perception (which is easy to imagine) and the reverse (which is harder to imagine). Chapter 4 is concerned with a tool to measure colour modularity: the use of isoluminant stimuli. The great problem with this particular tool is that one agrees upon the findings that both motion and stereopsis and some other specific form processes do not show up too well under isoluminance. They are supposed to be colour blind. But there is also good evidence that the phenomena do not disappear completely, as the theory of independent streams would require. There is a still ongoing debate about the possible causes of residual effects: optical and perceptual artefacts. Chapter 5 deals with the formation of temporary representations; especially the formation of a pictorial register. The pictorial register is a follow up of the iconic memory. The content of chapter 5 portrays a gradual shift from the feature-model of Treisman to a domain-model for the relevant modular input organization. Although the chapter reads rather easily, it is not easy to reproduce what is maintained precisely. While it is clear that the pure model of Treisman is not applicable, it is not clear whether the domain-concept is much better either. The issue of attention is complicated enough to fill books by itself. Chapter 5 makes an attempt to condense the discussion in less than 15 pages. At the end of chapter 5 and in chapter 6 there is a gradual transition to the important distinction between boundaries and surfaces or more precisely, Davidoff shifts from the ‘Marr-like’ modular approach to a ‘Grossberg-like’ non-modular approach of object recognition. The heart of the attention reallocation is in the boundary segmentation process. This process does not require object knowledge, and this gives the author the opportunity to place important other activities (like naming etc.) outside this central process. Chapter 7 is concerned with object knowledge: ‘Entry level representations’ form an important element in Davidoffs approach. The entry level representation is a representation ‘which would require the least perceptual analysis to build a detailed representation’. Special attention is paid to the separate location of the colour description. It is not a part of the entry level representation. This entry level description only contains information about shape and
Book reviews
293
size, i.e. boundary information, no information about surface properties like texture and colour. I found it difficult to summarize this chapter, although it certainly contains a lot of information. An essential part of the model introduced by Davidoff in chapter 8 is the Internal color space, a kind of reference centre for the colour description. It contains the colour palette of the observer, i.e. the categories, to be distinguished from the names given to the colours. The internal colour space is not simply related to either the neurophysiology of colour vision, nor to the names used for the colours. Davidoff refers to old literature (Sittig 1921) to distinguish colour agnosia from agnosia for colour names. The internal colour space has a similar function for object colours as the entry level representation has for objects. This level is different from the colour naming stage. This difference is important for the distinction between Colour Agnosia and Colour Name Amnesia. An interesting side step in this chapter has to do with the relations between colours and emotions, which are much less well established than is often assumed. In the next chapter Davidoff offers more evidence for his viewpoint that colour does not play a role at the entry level representation. There are a few tables in which many neuropsychological studies on object and colour recognition disturbances are summarized. Chapter 11 deals with the important topic of colour naming in normals and in brain-injured subjects. It describes the relatively late development in children of the full spectrum of colour names. For me the term Colour stupidity (the authors writes ‘color stupidly’ as a translation of Farbendummheit) was completely new. A description of the Whorf hypothesis is given and a number of interesting experiments in colour naming is summarized, before an overview is given of disorders in colour naming. Cognition through Color is a nice book to read several times if only because of the very extensive literature review in the area of central colour disorders which is rather difficult to access. Ch.M.M. de Weert NICI, University of Nijmegen P.O. Box 9104 6500 HE Nijmegen The Netherlands
Michael W. Eysenck (ed.), Wiley, Chichester, 1990.
Cognitive Psychology: An International Review.
The title that is given to this collection of review chapters is a bit misleading. Although the book is concerned with cognitive psychology, it is