Page:Mind (Old Series) Volume 11.djvu/548

 THE PERCEPTION OF SPACE BY DISP ABATE SENSES. 547 too short a line. The error varies within about the same limits as when the hand acts as the receiving sense. By combining the two conclusions we see that If the Eye is the expressing sense all lengtlis are greatly >i n derestimat e d, the error decreasing as the length increases. This is expressed on Fig. 5 by the fact that the two curves 2-1 and 3-1 are close together throughout. (2) If the Hand is the expressing sense, and (a) the Eye t/ie receiving sense, All lengths are greatly exaggerated, the error decreasing as the length increases [Fig. 5, 1-2] . That is, the attempt to hold the thumb and forefinger as far apart as the length of a line seen by the eye will result in holding the thumb and forefinger too far apart, the distance being more than double the true length in case of short lines. On the average, the lines were reproduced by dis- tances 144 per cent, of their true length. If the Hand is the expressing sense, and (b) the A r m the receiving sense, All lengths are greatly exaggerated, the error decreasing as the length increases [Fig. 5, 3-2] . That is, the attempt to hold the thumb and forefinger as far apart as the space moved over by a free arm movement (of the other arm) will result in holding the thumb and forefinger too far apart. 1 On the average, movements were reproduced by distances 168 per cent, of their true length. By combining the two results last obtained we see that If the Hand is the expressing sense, all lengths are greatli/ exaggerated, the error decreasing as the length increases. This is expressed on Fig. 5 by the close correspondence of the two curves 1-2 and 3-2. (3) If the A r m is the expressing sense, and (a) the Eye the receiving sense, All lengths are greatly exaggerated, the error decreasing as the length increases [Fig. 5, 1-31. That is, the attempt to move over a/ space equal to the length of a line seen by the eye will result in moving over much too large a space. On the average, a line will be reproduced by a space 185 per cent, of its true length. If the Arm is the expressing sense, and (b) the Hand the receiving sense, All lengths are greatly underestimated, the error decreas- ing as the length increases [Fig. 5, 2-3]. That is, the attempt to move over a space equal to the distance between thumb and fore- finger (of the other hand) will result in moving over much too 1 It is to be noted that although both sides of the body are involved in this operation, it makes little difference whether the right side acts as the .receiving sense and the left as the expressing sense, or vice versa.