Size-weight illusion among the blind. 
35 
succession the objects to be judged, and dropping them, if small, from 
one hand to the other, or by weighing them upon the tips of the fingers, 
as in the case of coins. In the methods of these experiments he had no 
previous experience. 
O was also fully aware of the illusion. He, like M, considered the 
third series of judgments the least satisfactory, and expressed the same 
preference for grasping rather than mere lifting upon the palm. O 
thought that size was less diverting in the first series than in the second. 
Experiments. 
(1) The first series of tests was that in which the knowledge of size 
was gained through the muscle sense, corresponding to Seashore’s 
“ fourth series, H, muscle sense.” An A and a B block, resting on end 
upon a soft pad, were lifted in succession, being grasped around the 
circumference by the thumb and middle finger of the right hand. If the 
weights were judged unequal, the B was replaced by another of the same 
set. Because the observer did not have to make any choice of B’s, but 
to consider only two blocks at a time (selected by the one conducting 
the experiment), he could fix his attention upon the question of equality 
of weight undistracted by the knowledge of the number of blocks that 
might possibly be compared. 
( 2 ) In another set of experiments the block was laid on the palm of