264 



PSYCHOLOGY. 



One of the situations in whicli we oftenest see tilings is 

 spread out on tlie ground before us. We are incessantly 

 drilled in making allowance for this perspective, and reduc- 

 ing tilings to tlieir real form in spite of optical foresliorten- 

 iug. Hence if the preceding explanations are true, we 

 ought to find this habit inveterate. The loiver half of the 

 retina, which habitually sees the farther half of thiugs 

 spread out on the ground, ought to have acquired a habit 

 of enlarging its pictures by imagination, so as to make 

 them more than equal to those which fall on the uj^per 

 retinal surface ; and this habit ought to be hard to escape 

 from, even when both halves of the object are equidistant 

 from the eye, as in a vertical line on paper. Delboeuf has 

 found, accordingly, that if we try to bisect such a line we 

 place the point of division about J^ of its length too high.* 



Similarly, a square cross, or a square, drawn on paper, 

 .should look higher than it is broad. And that this is actu- 

 ally the case, the reader may verify by a glance at Fig. 78. 



Fig. 78. 



For analogous reasons the upper and lower halves of the 

 letter S, or of the figure 8, hardly seem to differ. But when 

 turned upside down, as g, q, the upper half looks much the 

 larger, t 



* Bulletin de I'Academie de Belgique, 2me Serie, xix. 2. 



f Wundt seeks to explain all these illusions by tiie relatively stronger 

 ' feeling of innervation ' needed to move the eyeballs upwards, — a careful 

 Btudy of the muscles concerned is taken to prove this, — and a consequently 

 greater estimate of the aistance traversed. It suffices to remark, however, 

 with Lipps, that were the innervation all, a column of S's placed on top 

 of each other should look each larger than the one below it, and a weather- 

 cock on a steeple gigantic, neither of which is the case. Only the halves 

 of the same object look different in size, because the customary correction 



