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Colour and organisation: A response to King
New ldea~ in Psychol. Vol. 6, No. 3, pp. 289-291, 1988 Printed in Great Britain
0732-118X/88 $3.00+ 0.00 ~) 1988 Pergamon Press p[c
C O L O U R AND O R G A N I S A T I O N : A RESPONSE T O KING* GAETANO KANIZSA Institute of Psychology, University of Trieste, 34123 Trieste, Italy
O n the whole, I agree with the thesis p r o p o s e d by D. King (1988) in his article published in this j o u r n a l . After all, this thesis is very familiar to me, given my scientific b a c k g r o u n d which has been strongly influenced by the Gestalt-oriented teaching o f Cesare L. Musatti. Early on, Fuchs (1923a) suggested that assimilation p h e n o m e n a , especially c h r o m a t i c assimilation, are signs o f the f o r m a t i o n o f a perceptual whole. His article contains m u c h empirical evidence; o n e o f his d e m o n s t r a t i o n s is shown in Fig. 1. M o r e explicitly and m o r e generally, the same thesis was p r o p o s e d by Musatti in 1931, and t h e n e m p h a s i z e d again in 1953 on the basis o f new e x p e r i m e n t a l demonstrations.
@
@
@ YELLOW
@ @
@ @
@
RED
ORANGE
@
Fig. 1. The orange disk in the middle changes its color as a consequence of its figural belongingness. If it is perceived as a part of the vertical/horizontal red cross it looks reddish; if it is perceived as a part of the oblique yellow cross it looks yellowish (Fuchs, 1923b). A c c o r d i n g to Musatti, the s e g m e n t a t i o n o f the p e r c e p t u a l field into discrete units obeys a general principle that he calls the law of maximal homogeneity. W e r t h e i m e r ' s unification factors could be i n t e r p r e t e d as particular instances o f such a general principle o f organization. In o t h e r terms, this hypothesis implies that p e r c e p t u a l wholes are f o r m e d in such a way that the maximal h o m o g e n e i t y o f their qualitative aspects - - compatibly with proximal stimulus constraints - - is achieved. F u r t h e r m o r e , the resulting wholes exhibit a t e n d e n c y toward a *A commentary on D. L. King (1988) Assimilation is due to one perceived whole and contrast is due to two perceived wholes, Vol. 6, No. 3, pp. 277-288. 289
290
Gaetano Kanizsa
modification of their aspects in the direction of an increasing homogeneity, even beyond stimulus constraints, i.e., the law of maximal homogeneity implies not only organization according to maximal order but even a "forcing" of stimulus conditions. To support his hypothesis, Musatti mentions, in addition to Fuchs' demonstrations, the outcome of his experimental analysis of chromatic assimilation, a phenomenon originally observed by von Bezold (1876). Musatti holds that assimilation occurs when the inducing elements are "fragments" dispersed within the induced area. In such a case, fragments do not appear as independent units but contribute to generate the texture of a unitary whole. In fact, if the size of the fragments is increased, they become independent units, and contrast takes the place of assimilation. These results are confirmed by the work of Helson (1959, 1961), mentioned by King. Another confirmation of King's thesis can be considered as coming from transparency phenomena (Fuchs, 1923b; Kanizsa, 1955; Metelli, 1967). When the three opaque regions shown in Fig. 2(a) are juxtaposed as in 2(b), two phenomenal units arise: a light disk and a dark rectangle. It is possible to see one unit through a portion of the other, and the direction of transparency is reversible. The grey of the common area splits phenomenally into two colors, a light grey and a dark grey, each belonging to a homogeneously colored figure. This seems a clear instance of chromatic assimilation dependent upon or, more precisely, concomitant with the formation of perceptual wholes.
(a}
(b)
Fig. 2. The three opaque regions in (a) are perceived as two units when they are juxtaposed as in (b). Transparency can be seen in (b). Nevertheless, phenomena exist that apparently contradict King's hypothesis. In particular, I have in mind the Benary effect. Benary (1924) thought that phenomenal belongingness does not produce assimilation but, on the contrary, enhances contrast, Benary's interpretation is questionable, because this effect should not be attributed to belongingness but rather to another factor: contrast as a function of figure/ground organization (Wolff, 1934).
Colour and organisation: A response to King
291
Fig. 3. The Benary effect. The triangle on the black cross looks lighter than the triangle on the white ground. In Fig. 3, to say that o n e o f the grey triangles belongs to the cross and the o t h e r to the b a c k g r o u n d is not a phenomenologically correct description. It is m o r e c o r r e c t to say that the triangles are two i n d e p e n d e n t figures, each o n a d i f f e r e n t b a c k g r o u n d , o n e on the black cross, and the o t h e r on the white g r o u n d . W o l f f d e m o n s t r a t e d that contrast by the b a c k g r o u n d u p o n the figure is s t r o n g e r than contrast in the opposite direction. T h e r e f o r e , the first triangle appears lighter t h a n the second. I f this i n t e r p r e t a t i o n o f the B e n a r y effect is correct, its a p p a r e n t contradiction with King's thesis vanishes. REFERENCES Benary, W. (1924). Beobachtungen zu einem Experiment f b e r Helligkeitskontrast. Psychologische Forschung, 5, 131-142. von Bezold, W. (1876). The theory of color. Boston: Prang. Fuchs, W. (1923a). Experimentelle Untersuchungen fiber die A.nderung yon Farben unter dem Einfluss von Gestalten (Angleichungserscheinungen). Zeitschriftfiir Psycholog/e, 92, 249-325. Fuchs, W. (1923b). Untersuchungen fber das simultane Hintereinandersehen auf derselben Sehrichtung. Zeitschriftfiir Psychologie, 91, 145-235. Helson, H. & Rohles, F. H. (1959). A quantitative study of reversal of classical lightnesscontrast. American Journal of Psychology, 72, 530-538. Helson, H. & Joy, V. L. (1961). Domains of lightness, assimilation and contrast. Psychologische Beitriige, 6, 405--415. Kanizsa, G. (1955). Condizioni ed effetti della trasparenza fenomenica. Rivista di Psicologia, 49, 3-19. Metelli, F. (1967). Zur Analyse der ph~inomenalen Durchsichtigkeitserscheinungen. In: R. Miahlher and J. Fischl (Eds), Gestalt und Wirklichkeit. Berlin: Duncker und Humbolt. Musatti, C. (I 931). Forma e assimilazione. Archivio Italiano di Psicologia, 9, 213-269. Musatti, C. (1953). Ricerche sperimentali sopra ia percezione cromatica. Archivio di Psicologia Neurologia e Psichiatria, 14, 541-577. Wolff, W. (1934). Induzierte Helligkeitsveranderung. Psychologische Forschung, 20, 159--194.
0732-118X/88 $3.00+ 0.00 ~) 1988 Pergamon Press p[c
C O L O U R AND O R G A N I S A T I O N : A RESPONSE T O KING* GAETANO KANIZSA Institute of Psychology, University of Trieste, 34123 Trieste, Italy
O n the whole, I agree with the thesis p r o p o s e d by D. King (1988) in his article published in this j o u r n a l . After all, this thesis is very familiar to me, given my scientific b a c k g r o u n d which has been strongly influenced by the Gestalt-oriented teaching o f Cesare L. Musatti. Early on, Fuchs (1923a) suggested that assimilation p h e n o m e n a , especially c h r o m a t i c assimilation, are signs o f the f o r m a t i o n o f a perceptual whole. His article contains m u c h empirical evidence; o n e o f his d e m o n s t r a t i o n s is shown in Fig. 1. M o r e explicitly and m o r e generally, the same thesis was p r o p o s e d by Musatti in 1931, and t h e n e m p h a s i z e d again in 1953 on the basis o f new e x p e r i m e n t a l demonstrations.
@
@
@ YELLOW
@ @
@ @
@
RED
ORANGE
@
Fig. 1. The orange disk in the middle changes its color as a consequence of its figural belongingness. If it is perceived as a part of the vertical/horizontal red cross it looks reddish; if it is perceived as a part of the oblique yellow cross it looks yellowish (Fuchs, 1923b). A c c o r d i n g to Musatti, the s e g m e n t a t i o n o f the p e r c e p t u a l field into discrete units obeys a general principle that he calls the law of maximal homogeneity. W e r t h e i m e r ' s unification factors could be i n t e r p r e t e d as particular instances o f such a general principle o f organization. In o t h e r terms, this hypothesis implies that p e r c e p t u a l wholes are f o r m e d in such a way that the maximal h o m o g e n e i t y o f their qualitative aspects - - compatibly with proximal stimulus constraints - - is achieved. F u r t h e r m o r e , the resulting wholes exhibit a t e n d e n c y toward a *A commentary on D. L. King (1988) Assimilation is due to one perceived whole and contrast is due to two perceived wholes, Vol. 6, No. 3, pp. 277-288. 289
290
Gaetano Kanizsa
modification of their aspects in the direction of an increasing homogeneity, even beyond stimulus constraints, i.e., the law of maximal homogeneity implies not only organization according to maximal order but even a "forcing" of stimulus conditions. To support his hypothesis, Musatti mentions, in addition to Fuchs' demonstrations, the outcome of his experimental analysis of chromatic assimilation, a phenomenon originally observed by von Bezold (1876). Musatti holds that assimilation occurs when the inducing elements are "fragments" dispersed within the induced area. In such a case, fragments do not appear as independent units but contribute to generate the texture of a unitary whole. In fact, if the size of the fragments is increased, they become independent units, and contrast takes the place of assimilation. These results are confirmed by the work of Helson (1959, 1961), mentioned by King. Another confirmation of King's thesis can be considered as coming from transparency phenomena (Fuchs, 1923b; Kanizsa, 1955; Metelli, 1967). When the three opaque regions shown in Fig. 2(a) are juxtaposed as in 2(b), two phenomenal units arise: a light disk and a dark rectangle. It is possible to see one unit through a portion of the other, and the direction of transparency is reversible. The grey of the common area splits phenomenally into two colors, a light grey and a dark grey, each belonging to a homogeneously colored figure. This seems a clear instance of chromatic assimilation dependent upon or, more precisely, concomitant with the formation of perceptual wholes.
(a}
(b)
Fig. 2. The three opaque regions in (a) are perceived as two units when they are juxtaposed as in (b). Transparency can be seen in (b). Nevertheless, phenomena exist that apparently contradict King's hypothesis. In particular, I have in mind the Benary effect. Benary (1924) thought that phenomenal belongingness does not produce assimilation but, on the contrary, enhances contrast, Benary's interpretation is questionable, because this effect should not be attributed to belongingness but rather to another factor: contrast as a function of figure/ground organization (Wolff, 1934).
Colour and organisation: A response to King
291
Fig. 3. The Benary effect. The triangle on the black cross looks lighter than the triangle on the white ground. In Fig. 3, to say that o n e o f the grey triangles belongs to the cross and the o t h e r to the b a c k g r o u n d is not a phenomenologically correct description. It is m o r e c o r r e c t to say that the triangles are two i n d e p e n d e n t figures, each o n a d i f f e r e n t b a c k g r o u n d , o n e on the black cross, and the o t h e r on the white g r o u n d . W o l f f d e m o n s t r a t e d that contrast by the b a c k g r o u n d u p o n the figure is s t r o n g e r than contrast in the opposite direction. T h e r e f o r e , the first triangle appears lighter t h a n the second. I f this i n t e r p r e t a t i o n o f the B e n a r y effect is correct, its a p p a r e n t contradiction with King's thesis vanishes. REFERENCES Benary, W. (1924). Beobachtungen zu einem Experiment f b e r Helligkeitskontrast. Psychologische Forschung, 5, 131-142. von Bezold, W. (1876). The theory of color. Boston: Prang. Fuchs, W. (1923a). Experimentelle Untersuchungen fiber die A.nderung yon Farben unter dem Einfluss von Gestalten (Angleichungserscheinungen). Zeitschriftfiir Psycholog/e, 92, 249-325. Fuchs, W. (1923b). Untersuchungen fber das simultane Hintereinandersehen auf derselben Sehrichtung. Zeitschriftfiir Psychologie, 91, 145-235. Helson, H. & Rohles, F. H. (1959). A quantitative study of reversal of classical lightnesscontrast. American Journal of Psychology, 72, 530-538. Helson, H. & Joy, V. L. (1961). Domains of lightness, assimilation and contrast. Psychologische Beitriige, 6, 405--415. Kanizsa, G. (1955). Condizioni ed effetti della trasparenza fenomenica. Rivista di Psicologia, 49, 3-19. Metelli, F. (1967). Zur Analyse der ph~inomenalen Durchsichtigkeitserscheinungen. In: R. Miahlher and J. Fischl (Eds), Gestalt und Wirklichkeit. Berlin: Duncker und Humbolt. Musatti, C. (I 931). Forma e assimilazione. Archivio Italiano di Psicologia, 9, 213-269. Musatti, C. (1953). Ricerche sperimentali sopra ia percezione cromatica. Archivio di Psicologia Neurologia e Psichiatria, 14, 541-577. Wolff, W. (1934). Induzierte Helligkeitsveranderung. Psychologische Forschung, 20, 159--194.