Story of Psychology - Morton Hunt [301]
Even without such evidence, we can tell that movement perception is of paramount importance. Perception of our own movement guides us in making our way through our environment; perception of objects coming toward us enables us to escape harm; perception of the movement of our hands provides data vital to control when we are reaching for an object or doing fine manual work; perception of our minute bodily movements when standing keeps us from weaving or losing balance. (If you stand with your feet close together and shut your eyes, you will find it difficult to remain perfectly steady.)
Much research on movement perception for the past half-century has dealt with external variables: how the size, speed, location, and other characteristics of moving objects affect the way they appear to us. Such research is akin to psychophysics: it gathers objective data but says nothing of the internal processes responsible for the experiences. Still, it has provided important clues to those processes, both of the innate neural and the acquired cognitive kinds.
A typical finding about an innate low-level process: Researchers projected a shadow or boxlike figure on a screen in front of infants, then made the shadow or figure rapidly expand. When it did, the infants reared back as if to avoid being hit. The reaction is not a result of experience; a newborn who has never been hit by an approaching object will react in this fashion, as will many young and inexperienced animals. The avoidance response to a “looming” figure is evidently a protective reflex built into us by evolution; the visual impression of an object coming at us triggers escape behavior without involving higher mental processes.43
A typical finding about an acquired high-level process: In 1974 the psychologists David Lee and Eric Aronson built a floorless little room that could be slid one way or another across an unmoving floor. When they placed in it a toddler of anywhere from thirteen to sixteen months and slid the room in the direction he or she was facing—that is, away from the child’s face—the child would lean forward or fall; if they slid it in the other direction, the child would lean backward or fall. The explanation is that when the walls moved away, the child felt as if he or she were falling backward and automatically tried to compensate by leaning forward, and vice versa. This seems to be acquired behavior. The child learns to use “optic flow” information when beginning to walk. (Optic flow is the movement of everything within our visual field when we move. As we walk toward some point, for instance, everything around it expands outward toward the limits of our vision.)44
These and other fruitful studies of movement perception revealed additional defects of the long-held notion that the eye is a kind of camera. One such defect is that although the eye has no shutter, moving objects do not cause a blur, nor do we see a blur when we move our eyes as we do on a photograph if the camera is moved during exposure. Accordingly, much research on motion perception has sought to discover why there is no blurring. One hypothesis that gained favor was based on the finding by Ulric Neisser and various others that when we view an image flashed on a screen by a tachistoscope for even a tiny