PERCEPTION 



[6 53 



choose the 'brighter' of two targets of equal size and 

 will then immediately transfer this choice to the 

 larger of two targets differing in size but equal in 

 brightness. Similarly, moving one of two identical 

 targets further away, or interrupting its illumination, 

 say, once per second, will make this target equivalent 

 to a dimmer one. By such applications of converging 

 operations (method of equivalent-nonequivalent 

 stimuli) Kliiver was able to demonstrate the unusual 

 character of the visual world of the monkey with 

 occipital lesions, a mode of reacting never found in the 

 normal animal who perforce reacts to interdependent 

 dimensions in his visual field — 'shape' in spite of 

 varying orientations, 'size' with varying distance, 

 'brightness' with varying size, etc. (259). 31 



A corresponding state has been observed, at least 

 transiently, in man after massive occipital lesions. 

 The initial effect of large subtotal lesions of the 

 geniculostriate system in man is usually complete 

 blindness which recedes in minutes, days or (rarely) 

 weeks (386, 469). This recovery takes place in stages, 

 so that different aspects of perception return in a 

 regular sequence. First to recover is an undiffer- 

 entiated sensation of light [a reaction to total flux 

 (261)] without shape, color or localization in space. 

 After that, movement of a light mas be distinguished 

 from a stationary light, but the patient is still unable 

 to indicate direction or speed of the movement, and 

 thresholds for detection of movement are elevated. 

 Still later, localization of objects in visual space be- 

 comes possible, although with abnormal errors and 

 often with systematic distortions in the subjective 

 coordinates of perceptual space [see Fuchs ( 1 j!>] and 

 Teuber & Bender (473)]. At this stage, contours are 

 described as 'fuzzy' and unstable, and color is usualh 

 absent. Finally, contours take on a normal ap- 

 pearance, and color experiences become possible 

 (often after a period of intense red coloration of tin- 

 entire field — crythropsia). There are also reports of a 

 definite sequence in the recovery of different colors 

 [see Lhermitte & Ajuriaguerra (321)]. At no stage, 

 however, is there a selective loss of constancies; they 



31 It should ho noted that the extreme periphery of the 

 normal visual held of man also exhibits reactions to visual 

 flux, as proved by Gross & Weiskrantz 1 173). This observation 

 does not detract from the ingenuity of Kliiver's analysis (on 

 which it is based) but suggests that experiments on monkeys 

 should be repeated with further histologic controls to rule out 

 any possible escape of the most anterior parts of the striate 

 cortex. These regions, in the depth of the calcarine fissure, 

 probably represent the most peripheral portions of the visual 

 held, in man as well as in monkey. 



are absent only in the absence of perception of pat- 

 tern, depth and motion with which they are indis- 

 solubly linked. 



Deprivation and Recombination Studies 



If constancies as such are only abolished by total 

 destruction of projection systems, then one must 

 turn to evidence from isolation or rearrangement 

 studies in order to search for possible physiologic 

 correlates. Some constancies, e.g. those of perceived 

 velocity or visual direction, are clearly impaired 

 during and after the wearing of inverting or distorting 

 spectacles (285, 286}, or by short-term periods of 

 sensory deprivation (40, 205). Whether this is equally 

 true of other constancies, e.g. those of perceived color 

 or brightness, is not yet known. "Loss" of color con- 

 stancy in spectacle experiments is made unlikely by 

 the observation that the colored fringes induced 

 around borders in the field on wearing prismatic 

 spectacles tend to disappear with time, only to reap- 

 pear briefly (and in reverse orientation) when the 

 prisms are removed. A remarkable form of this 

 effect is (Collier's observation (285) with bipartite 

 red-and-green glasses, so worn that the left half of 

 each monocular held is green and the right half, red. 

 On turning the eves to the right, the observer sees 

 the world tinted in red, with eves turned to the left, 

 the world turns green. After several days of continued 

 wearing of these glasses, the color effects disappear, 

 Imt reappear in opposite fashion when the glasses are 

 taken oil, now the world looks green on turning the 

 eyes to the right, and red on turning them to the left. 

 These effects are thus specific, not for particular 

 areas of the visual field (as would be ordinary forms 

 of adaptation), but specific for particular ocular 

 postures. The results, if confirmed, would go beyond 

 any predictions derived from Hering's or Helson's 

 approach to chromatic adaptation and color con- 

 stancy. Kohler himself (285) speaks of "conditional 

 sensations," i.e. particular sensations that have be- 

 come associated with particular movements and 

 postures. These radical antichromatic responses (184), 

 although irreconciled with any current approach to 

 perception, may have parallels in other and better- 

 known phenomena. 



The moon-illusion, for instance, has been noticed 

 and discussed since antiquity. Moon and constella- 

 tions look large near the horizon and smaller near the 

 zenith. Artificial moons in a laboratory sky behave 

 analogously (416). The thorough analysis of the 

 phenomenon by Borina ( 54 ) revealed that the neces- 



