Page:Mind (Old Series) Volume 11.djvu/547

546 J. JASTROW : ^or arm) would be preferred which agreed with the results of the successive judgments. By this mode of reasoning, the curves for the right limit! and the left ana as the expressing senses were pre- ferred. 1 Another method of showing that the phenomenon is due to bilateral asymmetry of function, is to draw simultaneously lines with each hand, the attempt being to make the lines equal. Here as before the left arm draws the larger line, the error being slightly less when the lines are drawn towards than away from the body. The conclusions above discussed may be summarised thus : When the same, sense ad* us the receicing <nnl tin- c.fjir/'ssf///-/ st-nsr, tit/' error is small (and the process easy). In operations invoicing the u$e of both sides of the body, an interchange of the fund ion of thf tirn x/des rererst > the results ; when one liana, alone i-s used in succes- sive judgments, no such reversal takes place. The preferred Hand in span-sensations is the right; the preferred Arm in motion tin 1 lefl. The error of the Eye is less than that of the Hand ; the 4-ri'ar of the Hand slightly less than that of the Ann. II. When the receiving and expressing senses are different, (1) If the Eye !s the expressing sense, at/if (a) the Hand the receiving sen- . All length* tire great I y n n derest i mate d, the error t/. ing as Hit-, length increase* [Fig. 5, 2-1] . That is, if you attempt to mai'k off or select a length by the eye equal to the distance between your thumb and forefinger, the selected lengths will be too short ; in case of small distances only about one-half the real length. The lines thus selected varied from about 48 per cent, to 88 per cent, of the true distance between thumb and forefinger the average being about 65 per cent. 2 If the E ij e is the expressing sense, aitd (b) //// .-1 / /// the receicing sense, All lengths an' g r / a t / ij n n d e r c s t ! tn a t e d, the ermr ilecrrasing as tin' length literease* [Fig. 5, 3-1] . That is, the attempt to mark off or select by sight a line equal to the space moved over by a free arm movement will result in selecting or marking off much 1 The successive judgments were made by the Hand, by first grasping a block between tluiiid) and forefinger and thru adjusting the carriages of the Span-triangle, to match tin- Muck fell ; by the Arm, l.iy attempting to draw (with eyes rinsed) the second of a pair of lines equal to the first, using the apparatus shown in Fig. 1'. Tn l>oth these- cases it makes little difference which hand or arm is used. All those experimented upon vcre right-handed. -The lines were selected on the Bight-triangle OT mai'ked off on ruled ]>aper, the im]ires.-ion liein- received by the 1'i^ht or the left hand. By these four methods a length of 15mm . was reproduced hy lines 4<; ju-r cent., 36 Iier cent., 37 jier cent, and 3 1 per cent, of the real length ; of 110 mm. by im-s S-J jicr cent., 80 jier ecu!., S7 per cent, and ^ per cent, of the real length. The close correspondence of these, numbers is an indication of the regularity of the processes involved.