The Perception of Motion when 
We Are in Motion
When we are moving, things 
appear to move in the direction 
opposite to our movement.

In many instances, we are the 
ones in motion, not the objects 
around us. When we move, all 
objects change their direction 
with respect to our position. 
Thus, according to the general 
rule of motion perception, they 
ought to appear to move. 
Instead, however, our 
perceptual system attributes 
the change in the direction of 
things to our own motion. For 
any given movement of our 
own, an object at a particular 
distance will undergo a 
particular change in its 
direction and will do so at a 
particular rate (motion 
parallax). As long as the object’s 
distance is perceived correctly, 
it will appear to remain 
stationary. Thus, position 
constancy is achieved. For 
example, an object seen 
straight ahead and close by will 
"go" to the observer’s left at a 
fairly rapid rate as the observer 
moves to the right. Does this 
mean that, if the object were 
perceived to change its 
direction differently or at a 
different rate with this same 
movement of the observer, it 
would appear to move? It is 
plausible to believe that it 
would, and in fact we know 
that it would.