was in sight, and the afterimage of this again lasted until the third came. The after-
images were responsible for the fact that no interruption was noticeable, while the
movement itself resulted simply from the passing of one position into another. What
else is the perception of movement but the seeing of a long series of different posi-
tions? If instead of looking through the Zoetrope we watch a real trotting horse on a
real street, we see its whole body in ever-new progressing positions and its legs in all
phases of motion; and this continuous series is our perception of the movement it-
self.Munsterberg wryly comments on the theory:“This seems very simple. Yet it
was slowly discovered that the explanation is far too simple...”
Munsterberg put the crux of the critique (which has basically stood to today,
although many film scholars seem unaware of it) succinctly as,“The perception
of movement is an independent experience which cannot be reduced to a simple
seeing of a series of different positions.”Munsterberg claims that a“higher
mental act”is superadded to the physiological process, which he admits does
not fully explain the phenomenon.While contemporary theories of perception
do not deny the phenomenon of an afterimage and the apparent motion that the
older theory sought to explain, they agree that simply retaining a series of after-
images in different positions cannot automatically yield a moving image (the
effect would more likely be that of multiple superimpositions). Contemporary
theories have broken the motion into multiple interrelating factors, whose com-
plexities still allow some degree of controversy and uncertainty, even if the in-
adequacy of the old theory cannot be disputed. As the Andersons show, the
phenomenon of persistence of vision as the explanation of the continuous mov-
ing image can be broken into two issues:
Why is the image continuous, and why does it move? In other words, why do the
separate frames appear continuous rather than as the intermittent flashes of light
which we know them to be? And why do the figures on the screen appear to move
about in smooth motion when we know they are in fact still pictures?Not long after the emergence of cinema, perceptual psychology already sup-
plied alternative explanations to the persistence of vision thesis, as Munsterberg
was aware. InMax Wertheimer took up the issue of apparent motion and
his critique of the persistence of vision theory inaugurated the beginning of Ge-
stalt psychology by questioning the mechanistic assumptions of previous per-
ceptual psychology. Wertheimer attributed apparent motion to three factors,
summarized by the Andersons as: () beta movement (the object at A seen as
moving across the intervening space to position B), () partial movement (each
object seen moving a short distance), and () phi movement (objectless or pure
motion).Writing more recently R.L. Gregory’s classic account of visual per-
30 Tom Gunning