The most interesting case of this in visual perception is that of a disturbance or displacement of the organ by external force.

For example, an illusory sense of direction arises by the simple action of closing one eye, say the left, and pressing the other eyeball with one of the fingers a little outwards, that is to the right.

The result of this movement is, of course, to transfer the retinal picture to new nervous elements further to the right.

And since, in this instance, the displacement is not produced in the ordinary way by the activity of the ocular muscle making itself known by certain feelings of movement, it is disregarded altogether, and the direction of the objects is judged as though the eye were stationary.
A somewhat similar illusion as to direction occurs in auditory perception.

The sense of direction by the ear is known to be due in part to the action of the auricle, or projecting part of the ear.