96 TITCHENER AND PYLE— JUDGMENT OF DISTANCE. [April 18, 



ingly, found its way, as matter of proved fact, into the current ' litera- 

 ture ' of psychology/ This circumstance alone is a justification 

 for the reopening of the whole question. 



Apparatus and Method. 



It is clear that the conditions of the experiment may be met in 

 two different ways. Either the white background may be made 

 translucent, and the shadows shown from behind by transmitted 

 light; or the background may be made sensibly opaque, and the 

 shadows thrown upon it from the front. Both forms of apparatus 

 were employed by Dunlap : our own experiments, for reasons which 

 will be given later, were performed only with an apparatus of the 

 first type. In order that the two sets of results might be compar- 

 able, we at first set up this apparatus in accordance with Dunlap's 

 description, and reproduced his method of work. 



A sheet of white bristol-board, 58 by y2 cm., was mounted hori- 

 zontally in a black wooden frame. Across the middle of the sheet 

 was drawn a black line, i mm. in width, which was crossed at the 

 centre by a vertical black line, 0.75 mm. wide and 17 mm. long. To 

 the sides of the frame, at the level of the horizontal line, were 

 fastened guides, in which ran small rods of blackened steel : the 

 rods could be drawn in or out along the line, and were of course 

 invisible against it. The inner ends of the rods carried vertical 

 strips of black paper, 2 mm. wide and 10 mm. long. These strips, 

 like that at the centre, extended equally above and below the hori- 

 zontal line ; and the three together marked off the two sections of 

 that line whose lengths the observer should presently be called upon 

 to compare. A mm. scale, attached to the frame above the rods, 

 and a small marker on the rods themselves, made it possible to set 

 the limiting strips, with accuracy, to any required position. 



^ We may mention G. M. Stratton, " Experimental Psychology and its 

 Bearing upon Culture," 1903, 88 ff. ; J. Jastrow, " The Subconscious," 1906, 

 417 ff. ; J. B. Pratt, " The Psychology of Religious Belief," 1907, 20. Dunlap's 

 results are accepted by M. Meyer ("Aus den Versuchsergebnissen geht mit 

 Deutlichkeit hervor, dass auch in solchem Falle die Illusion stattfindet "), in 

 Zcits. f. Psychol, nnd Physiol, d. Sinnesorg., XXV., 1901, 266; by A. Meyer, 

 in Journal of Philos., Psychol, and Sci. Methods, IV., 1907, 80 f. ; by the 

 anonymous reviewer in Mind, N. S., X., 1901, 281 ; and, although with more 

 reserve, by J. Philippe, in Rev. philos., 1901, 341. We are not aware that they 

 have as yet been incorporated in any formal text-book of psychology. 



