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Perceiving events and objects
am
psychologica ELSEVIER
Acta Psychologica 92 (1996) 223-225
Book review G. Jansson, S.S. BergstriSm and W. Epstein (Eds.), Perceiving Events and Objects. Erlbaum, Hillsdale, NJ, 1994. Although it is not obvious from the title, this book centers around Gunnar Johansson's work in the area of event and slant perception. In August 1991, a symposium was held at his homebase, Uppsala University, to celebrate his 80th birthday. Despite Gunnar's dislike of Festschriften, the present collection of papers is basically a Festschrift in his honor but in a very original way. After a biographical chapter in the form of an interview (by Epstein), a good deal of Johansson's publications is reprinted (taking up 268 pages of the book), followed by an extensive (197 pages) discussion of his work by some internationally renown perceptual scientists (Braunstein, Epstein, Held, Hochberg, Koenderink, Lappin, Lee, Leibowitz, Todd) and many of Johansson's former and present collaborators (Bergstrtim, BiSrjesson, Jansson, Rumar, Runeson, von Hofsten). The book concludes with some personal comments by Johansson stimulated by the preceding contributions and an exhaustive (?) bibliography. A Festschrift can only be as interesting as the person and work of the one who is celebrated. In the case of Johansson, the basic conditions to get an excellent book are there. Johansson himself is an interesting man. Before starting his university studies at the age of 29, he has worked in his father's general store. After obtaining his undergraduate degree in philosophy, he has been director of a vocational guidance bureau for three years. Then he went to the University of Stockholm to work with David Katz to get a doctoral degree in psychology with a thesis on the perception of real motion (defended in 1950, at the age of 39). His remarkable originality as a scientist as well as his practical orientation might well be the result of this non-typical student career. Indeed, in this book, it becomes clearer than ever that Johansson's work is hard to classify within the standard metatheoretical frameworks: It is a unique mixture of ideas from Gestalt psychology with concepts inspired by Gibson's ecological and Marr's computational approach. Johansson himself admits that he has been 'an ensam varg (a lone wolf)'. His practical orientation becomes evident when one learns that Johansson had to build all his apparatus for his PhD work himself and that he has been the Swedish pioneer in human factors research in aviation (e.g., joystick use) and car driving (e.g., vehicle lighting, road signs, braking). During his lifelong career of almost half a century, Johansson has studied a large 0001-6918/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0 0 0 I - 6 9 l 8 ( 9 5 ) 0 0 0 4 1 - 0
224
Bookreview
number of problems in the area of visual event perception. His major contributions fall into three categories: (I) the perception of simple configurations in motion (exemplified by his PhD thesis which was published as a book in 1950), (2) the perception of biological motion (exemplified by his 1973 paper in Perception & Psychophysics), and (3) wide-angle space perception (exemplified by his paper with BSrjesson in Ecological Psychology, 1989). Despite the apparent diversity of these empirical problems, there is a solid theoretical basis for all of them: decoding principles of the vector-analysis type for (1) and (2) and optic sphere theory for (3). In Chapter 11 of the present book, Johansson even attempts to integrate both. In 1986, Johansson received the Award for Distinguished Scientific Contributions from the A.P.A. At that time, he had only just started his work on wide-angle space perception and the optic sphere. Nevertheless, this is Johansson's most ambitious project (as evidenced by the 1989 paper's title 'Toward a new theory of vision') in the light of which the rest of his work is called 'that old stuff'. Basically, the optical sphere theory consists of two parts, one geometrical and the other neurophysiological. First, a spherical projection surface is used to characterize the array of light reflected from the environment at the nodal point of the eye. Second, a neurophysiological processor of the smart-mechanism type is postulated that is able to measure the structure of this array relative to the eye and the direction of gravity (requiring an interaction or 'overhearing' between visual and kinesthetic perception). According to Johansson, this theory will provide a conceptual revolution because it is the first which takes the hemispherical shape of the retina of the vertebrate eye seriously. Almost all we know about visual perception so far is restricted to foveal or parafoveal vision for which a flat surface is a valid approximation. However, for wide-angle space perception tasks such as slant estimation, the picture-plane and retinal-image assumptions are clearly deficient. As this book demonstrates, the optic sphere theory is still in a state of progress and it remains to be seen whether it will form the radical departure from previous theorizing which the authors hope it will be (and some of their commentators doubt it will be). How useful is it to have a collection of reprints of Johansson's publications? I think it is very useful if one does not have Johansson's 1950 monograph. It has been out of print for about 30 years and it proves to be a classic in all respects. It is one of those inspiring works in which a well-delineated problem, the search for perceptual principles determining visual event configurations, is tackled by a step-by-step progressing series of well-designed experiments, interspersed with gradually more elaborated theorizing. It reminds one of Michotte's opus magnum, La perception de la causalitg (1946), which happens to be the core of a previous volume in the same series Resourcesfor Ecological Psychology (Thinbs et al., 1991). Chapter 2 in the present book is a precis of the original 1950 monograph, produced by Johansson himself. The most relevant sections are reprinted word-for-word while others are only summarized or even excluded altogether; some comments are added too. The other chapters in this section are reprints from more accessible journals such as Acta Psychologica, Scandinavian Journal of Psychology, Perception, Psychological Research, etc. It is nice to have all of them together within the same cover but one can find the papers just as well in a good university library. The reprint section closes with an unpublished recent paper on the relation between vector analysis and the optic sphere theory.
Book review
225
How useful is it to have a collection of commentaries on Johansson's work? Here I am less convinced. Despite Johansson's explicit wish to have the invited symposium participants "read his work and criticize it rather than act as devotees or present their work" (p. ix), my impression is that most of the chapters are, at best, a mixture of both possibilities. Most Swedish contributors have taken the chance to highlight their own work and point out how they have collaborated with or have been inspired by Johansson. Most other contributors discuss the relationship between their own work and Johansson' s, sometimes with the focus being on Johansson's work (e.g., Koenderink), sometimes with the focus being on their own work (e.g., Hochberg). In all cases, the contributors have retained their own personal writing styles. For example, Koenderink's chapter is an elegant mathematical examination of the power and simplicity of vector analysis for solving the shape-from-motion problem. Hochberg's chapter is a discussion of some perceptual phenomena discovered by Johansson from Hochberg's preferred theoretical framework of cognitive processing (e.g., perceptual intention, hidden rules, mental structure). The chapter by von Hofsten and Lee is a dialogue (with 13 mathematical equations!) on the measurement of distance with (and without) the optic sphere. This conversation style is a format which they have used in another book chapter in the same series (von Hofsten and Lee, 1985). In short, given the importance of Johansson's work for any student in perception, this book is recommended to all those who have time to get acquainted with his research (in case the fascinating point-light walker display would be the only thing you know about it) or to gather a deeper understanding of it (in case you are already familiar with his vector analysis model or his optic sphere theory). Johan Wagemans University of Leuven Laboratory of Experimental Psychology Tiensestraat 102 B-3000 Leuven Belgium E-mail: johan.wagemans @psy.kuleuven.ac.be
References Thinbs, G., A. Costall and G. Butterworth (eds.), 1991. Michotte's experimental phenomenology of perception. Hove: Erlbaum. von Hofsten, C. and D.N. Lee, 1985. 'Dialogue on perception and action'. In: W. H. Warren, Jr. and R.E. Shaw (eds.), Persistence and change: Proceedings of the First International Conference on Event Perception (pp. 231-242). Hillsdale, NJ: Edbaum.
psychologica ELSEVIER
Acta Psychologica 92 (1996) 223-225
Book review G. Jansson, S.S. BergstriSm and W. Epstein (Eds.), Perceiving Events and Objects. Erlbaum, Hillsdale, NJ, 1994. Although it is not obvious from the title, this book centers around Gunnar Johansson's work in the area of event and slant perception. In August 1991, a symposium was held at his homebase, Uppsala University, to celebrate his 80th birthday. Despite Gunnar's dislike of Festschriften, the present collection of papers is basically a Festschrift in his honor but in a very original way. After a biographical chapter in the form of an interview (by Epstein), a good deal of Johansson's publications is reprinted (taking up 268 pages of the book), followed by an extensive (197 pages) discussion of his work by some internationally renown perceptual scientists (Braunstein, Epstein, Held, Hochberg, Koenderink, Lappin, Lee, Leibowitz, Todd) and many of Johansson's former and present collaborators (Bergstrtim, BiSrjesson, Jansson, Rumar, Runeson, von Hofsten). The book concludes with some personal comments by Johansson stimulated by the preceding contributions and an exhaustive (?) bibliography. A Festschrift can only be as interesting as the person and work of the one who is celebrated. In the case of Johansson, the basic conditions to get an excellent book are there. Johansson himself is an interesting man. Before starting his university studies at the age of 29, he has worked in his father's general store. After obtaining his undergraduate degree in philosophy, he has been director of a vocational guidance bureau for three years. Then he went to the University of Stockholm to work with David Katz to get a doctoral degree in psychology with a thesis on the perception of real motion (defended in 1950, at the age of 39). His remarkable originality as a scientist as well as his practical orientation might well be the result of this non-typical student career. Indeed, in this book, it becomes clearer than ever that Johansson's work is hard to classify within the standard metatheoretical frameworks: It is a unique mixture of ideas from Gestalt psychology with concepts inspired by Gibson's ecological and Marr's computational approach. Johansson himself admits that he has been 'an ensam varg (a lone wolf)'. His practical orientation becomes evident when one learns that Johansson had to build all his apparatus for his PhD work himself and that he has been the Swedish pioneer in human factors research in aviation (e.g., joystick use) and car driving (e.g., vehicle lighting, road signs, braking). During his lifelong career of almost half a century, Johansson has studied a large 0001-6918/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved SSDI 0 0 0 I - 6 9 l 8 ( 9 5 ) 0 0 0 4 1 - 0
224
Bookreview
number of problems in the area of visual event perception. His major contributions fall into three categories: (I) the perception of simple configurations in motion (exemplified by his PhD thesis which was published as a book in 1950), (2) the perception of biological motion (exemplified by his 1973 paper in Perception & Psychophysics), and (3) wide-angle space perception (exemplified by his paper with BSrjesson in Ecological Psychology, 1989). Despite the apparent diversity of these empirical problems, there is a solid theoretical basis for all of them: decoding principles of the vector-analysis type for (1) and (2) and optic sphere theory for (3). In Chapter 11 of the present book, Johansson even attempts to integrate both. In 1986, Johansson received the Award for Distinguished Scientific Contributions from the A.P.A. At that time, he had only just started his work on wide-angle space perception and the optic sphere. Nevertheless, this is Johansson's most ambitious project (as evidenced by the 1989 paper's title 'Toward a new theory of vision') in the light of which the rest of his work is called 'that old stuff'. Basically, the optical sphere theory consists of two parts, one geometrical and the other neurophysiological. First, a spherical projection surface is used to characterize the array of light reflected from the environment at the nodal point of the eye. Second, a neurophysiological processor of the smart-mechanism type is postulated that is able to measure the structure of this array relative to the eye and the direction of gravity (requiring an interaction or 'overhearing' between visual and kinesthetic perception). According to Johansson, this theory will provide a conceptual revolution because it is the first which takes the hemispherical shape of the retina of the vertebrate eye seriously. Almost all we know about visual perception so far is restricted to foveal or parafoveal vision for which a flat surface is a valid approximation. However, for wide-angle space perception tasks such as slant estimation, the picture-plane and retinal-image assumptions are clearly deficient. As this book demonstrates, the optic sphere theory is still in a state of progress and it remains to be seen whether it will form the radical departure from previous theorizing which the authors hope it will be (and some of their commentators doubt it will be). How useful is it to have a collection of reprints of Johansson's publications? I think it is very useful if one does not have Johansson's 1950 monograph. It has been out of print for about 30 years and it proves to be a classic in all respects. It is one of those inspiring works in which a well-delineated problem, the search for perceptual principles determining visual event configurations, is tackled by a step-by-step progressing series of well-designed experiments, interspersed with gradually more elaborated theorizing. It reminds one of Michotte's opus magnum, La perception de la causalitg (1946), which happens to be the core of a previous volume in the same series Resourcesfor Ecological Psychology (Thinbs et al., 1991). Chapter 2 in the present book is a precis of the original 1950 monograph, produced by Johansson himself. The most relevant sections are reprinted word-for-word while others are only summarized or even excluded altogether; some comments are added too. The other chapters in this section are reprints from more accessible journals such as Acta Psychologica, Scandinavian Journal of Psychology, Perception, Psychological Research, etc. It is nice to have all of them together within the same cover but one can find the papers just as well in a good university library. The reprint section closes with an unpublished recent paper on the relation between vector analysis and the optic sphere theory.
Book review
225
How useful is it to have a collection of commentaries on Johansson's work? Here I am less convinced. Despite Johansson's explicit wish to have the invited symposium participants "read his work and criticize it rather than act as devotees or present their work" (p. ix), my impression is that most of the chapters are, at best, a mixture of both possibilities. Most Swedish contributors have taken the chance to highlight their own work and point out how they have collaborated with or have been inspired by Johansson. Most other contributors discuss the relationship between their own work and Johansson' s, sometimes with the focus being on Johansson's work (e.g., Koenderink), sometimes with the focus being on their own work (e.g., Hochberg). In all cases, the contributors have retained their own personal writing styles. For example, Koenderink's chapter is an elegant mathematical examination of the power and simplicity of vector analysis for solving the shape-from-motion problem. Hochberg's chapter is a discussion of some perceptual phenomena discovered by Johansson from Hochberg's preferred theoretical framework of cognitive processing (e.g., perceptual intention, hidden rules, mental structure). The chapter by von Hofsten and Lee is a dialogue (with 13 mathematical equations!) on the measurement of distance with (and without) the optic sphere. This conversation style is a format which they have used in another book chapter in the same series (von Hofsten and Lee, 1985). In short, given the importance of Johansson's work for any student in perception, this book is recommended to all those who have time to get acquainted with his research (in case the fascinating point-light walker display would be the only thing you know about it) or to gather a deeper understanding of it (in case you are already familiar with his vector analysis model or his optic sphere theory). Johan Wagemans University of Leuven Laboratory of Experimental Psychology Tiensestraat 102 B-3000 Leuven Belgium E-mail: johan.wagemans @psy.kuleuven.ac.be
References Thinbs, G., A. Costall and G. Butterworth (eds.), 1991. Michotte's experimental phenomenology of perception. Hove: Erlbaum. von Hofsten, C. and D.N. Lee, 1985. 'Dialogue on perception and action'. In: W. H. Warren, Jr. and R.E. Shaw (eds.), Persistence and change: Proceedings of the First International Conference on Event Perception (pp. 231-242). Hillsdale, NJ: Edbaum.