INDUCED SELF-MOTION 
Slow displacement of an 
adjacent train is often 
experienced as motion in the 
opposite direction of the train 
in which we are sitting.  The 
adjacent train then appears to 
be stationary.

We ourselves sometimes 
undergo induced motion. When 
we are in a stationary train and 
a train on the adjacent track is 
in motion, for example, we 
often misperceive which train 
is actually moving. A similar 
effect occurs when we stop for a 
light in a car. If a car alongside 
ours begins to roll backward, 
we often perceive our own car 
to be rolling forward and step 
on the brakes. When we look 
down at the water current from 
a stationary boat or from a pier, 
we sometimes experience 
ourselves as in motion.

    Induced motion of the self 
was demonstrated in the 
Haunted Swing Illusion, an 
exhibition at an 1894 fair in 
San Francisco. Observers sat in 
a large seat suspended by ropes. 
The seat seemed to swing back 
and forth in ever increasing 
arcs until eventually it turned 
upside down. No one fell off--
for the simple reason that the 
swing only moved slightly. It 
was the room that swung back 
and forth. The people on the 
swing experienced themselves 
as in motion and the room as 
stationary. In this example, the 
induction effect is powerful 
enough to overcome 
information based on gravity, 
which indicates that the 
observers are not tilting or 
inverting and that the room is 
tilting from the upright.