1652 



HANDBOOK OF PHYSIOLOGY 



M I ROPHYSIOLOGY III 



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FIG. :j5- Effects of 'reduction' on apparent size, summarizing 

 experimental results of llolway & Boring (230). The ordinate, 

 S c , gives the diameter in inches of the comparison stimulus 

 equated in apparent size to the diameter of a standard stimulus 

 (subtending 1°). The comparison stimulus is kept at 10 ft. 

 from the observer. Abscissa values indicate the various distances 

 in feet from the observer at which the standard stimulus was 

 pi. ned. The oblique broken line defines the locus of all results 

 obeying the 'law of size constancy'; the horizontal broken line, 

 all results obeying the law of the visual angle. There was 

 slight "overconstancy' on free binocular regard, but progres- 

 sively less constancy as increasingly severe conditions of "re- 

 duction' were imposed. [Modilied from Holway & Boring 

 (220).] 



[joint, suggested we substitute the term 'compensa- 

 tion.'] Alley trees do converge towards the horizon 

 (as do railroad tracks), although we can also see that 

 they are equidistant. Can we see both at once, or do 

 we see convergence and equidistance in alternation, 

 'at will,' depending on our attitude (55)? Perhaps 

 we do sec both but say two things when we stop to 

 talk about it; immediate perception, even in the 

 normal state, has these elements of 'unreasonable- 

 ness' that loom so much larger in the spectacle experi- 

 ments [see above (285)]. To paraphrase an earlier 

 statement, if perception did not have certain non- 

 geometric (or, at least non-Euclidean features), the 

 discovery of geometry by Euclid and his predecessors 

 would have been less of an invention."' If maximal 

 reduction as in the Holway-Boring experiment throws 

 the perceiver back upon a perspective mode of 

 seeing (155), this does not mean that this mode is 

 more 'basic' than the normal multidetermined mode 

 of perceiving. It is probable that there is no reduction 

 radical enough to abolish simultaneously all con- 

 stancies without abolishing pattern, depth and 

 motion, i.e. without rendering size and distance in- 

 determinate. 



of the experimental arrangement. Moving one's eye 

 while looking at the (real) distorted room, or moving 

 one's hand with a stick through the room, touching 

 various parts, leads to .1 perception of the slant, and 

 a 'correct' (undistorted) view of the heads. 



The most systematic study of 'reduction' in its 

 effect on size constancy is that by Holway & Boring 

 (220). They measured the apparent size of a standard 

 disk (subtending a visual angle of one degree) as the 

 distance of the standard was varied from 10 to 120 

 It. in a long corridor. The functions relating apparent 

 size to distance were obtained under free binocular 

 viewing conditions; these functions showed nearly 

 complete constancy (see fig. 33). The measurements 

 were then repeated under conditions that, in the 

 opinion of Holway & Boring (220), represented a 

 serial reduction of size perception, viz. u) under 

 monocular regard; /') monocular, with small ai'tilichil 

 pupil; and c) monocular, with artificial pupil and a 

 long black reduction tunnel. As the reductions in- 

 c i' ased, the Constancy effect declined and approached 



'I ndition c) the 'law ol retina] image size' (or 



visual angle I 



In discussing these results, the authors point out 



thai constancy (e.g ol size) is in most c.iscs .1 hypo 

 bolic expression. [Helson (196) making the s.mic 



Loss of Cons/au* 11 1 Aftet Cerebral l.tsions 



Such a condition is probably realized after total 

 destruction of the primary projection system. Alter 

 bilateral occipital lobectomy, monkeys react to light, 

 in fact, as if there were no constancies, but merely 

 luminous flux (261). As Kliiver (261 ) points out, this 

 residual visual capacitv must not be described as a 

 preservation of perception of •brightness' in the 

 absence of all patterning, since brightness implies 

 ability to react to flux per unit area, regardless of 

 wide variations in the area on which the brightness 

 appears, its shape or its distance. Thus, the monkey 

 with bilateral occipital lesions can be trained to 



"' l.iinebui g (330) has, in fact, attempted to describe 

 perceived (binocular) space .is non-Euclidean. Lunching 

 devised .1 three-dimensional bipolar coordinate system to 

 encompass the results of Hillebrand's (313) and Blumenfeld's 

 (.|q! famous alley experiments; apparent parallel alleys (of 

 luminous dots in a d.nk room) are physically narrowei than 

 alleys set t<> appeal "! tin- same width. By luting this peculiar 

 situation into .1 non-Euclidean (hyperbolic) space (in which 



tile parallel axiom does not hold 1 . Lunching hoped to derive .1 



general metric ol binocular space where size constancy would 

 lollou Brora its particulai geometry I mpirical tests of l.une- 

 burg's approach have yielded somewhat discordant results 

 < 179. !-:• i- !l 



