In the case of a negative afterimage the light impression leaves a dark spot, the dark impression gives a light afterimage.

Black becomes white and white becomes black; in the world of colors red leaves a green and green a red afterimage, yellow a blue and blue a yellow afterimage.

If we look at the crimson sinking sun and then at a white wall, we do not see red light spots but green dark spots.
Compared with these negative pictures, the positive afterimages are short and they last through any noticeable time only with rather intense illumination.

Yet they are evidently sufficient to bridge the interval between the two slits in the stroboscopic disk or in the zooetrope, the interval in which the black paper passes the eye and in which accordingly no new stimulus reaches the nerves.

The routine explanation of the appearance of movement was accordingly: that every picture of a particular position left in the eye an afterimage until the next picture with the slightly changed position of the jumping animal or of the marching men was in sight, and the afterimage of this again lasted until the third came.