In experiments such as 
Stratton performed, observers 
will adapt to this abnormal 
change in direction during 
their movement. After a few 
days, the scene no longer 
appeared to Stratton to move 
when he moved. It was not 
simply that he grew accustomed 
to such motion effects and 
stopped attending to them. The 
proof is that, on removing the 
lenses at the end of the 
experiment, the scene 
appeared to move whenever 
Stratton moved and in a 
direction opposite to the 
direction in which it appeared 
to move when he first put the 
lenses on. This kind of 
outcome, of perceiving things 
opposite to the way they 
appeared when distorting 
optical devices were worn 
(generally referred to as a 
negative aftereffect), can be 
taken as strong proof that an 
adaptive change has occurred. 
We can therefore conclude that 
Stratton’s perceptual system 
learned, while he was wearing 
inverted lenses, that the 
change of direction of 
stationary things during his 
own movement is toward the 
direction of his movement, not 
opposite to it, as is normally 
the case.