Movement Science

Are parents ready to red shirt there children? No, I’m not talking about sports but kindergarten. Many parents are facing the issue of whether or not their children are ready for the big step into the classroom. Before entering kindergarten children need to develop their perceptual skill (depth perception). As humans we need depth perception for detection, discrimination, and identification of objects. Depth perception is a difficult topic to access due to the fact that the world is three dimensional and human visions are two dimensional. When transmitted to the brain, an image on the retina is not a picture; rather it is a pattern of nerve impulses, aroused by a light pattern that terminates in the visual area of the cerebral cortex. Through some activity of the occipital lobes of the cerebral cortex, human beings apparently perceive the external world in a three-dimensional manner that is correlated with the retinal-image pattern in some orderly manner.

Psychologists are particularly interested in the cues which enable people to perceive depth and distance. Stimulus patterns for arousing a depth experience occur when individuals are given specific cues. The cues may be monocular, effective when using one eye as well as two, or binocular, requiring the usage of both eyes. The cues may also be psychological, depending only on the visual image, or physiological, originating from the structure and movement of the eyes.

In this paper I will explain perceptual development and how it relates to animals, infants, and blind infants. Infancy is the period of life in which development occurs most rapidly. Development occurs in a variety of different ways and has been categorized with the study of infancy into physical, motor, and perceptual development. Each of these forms of development occurs simultaneously and progress in each facilitates the progress of the other. There are many studies I will assess to further explain how they contribute to explaining the development of perception.

In developing direct perception one must be able to directly perceive what the objects and surfaces in the environment are perceived as an action of affordances. An example of an affordance is stair climbing. Walking down a flight of stairs as an 18 month and adult are different. As an individual grows, perception of affordances might change. When climbing the stairs a person must be able to judge leg length to judge how they climb the stairs. Oculomotor and visual cues help us solve this problem as sources of depth perception. Oculomotor is broken down into convergence and accommodation. The amount of convergence and accommodation can be used as cues for absolute depth (for objects not too far away from you). Visual cues can be broken down into binocular and monocular.

Binocular visual fields make use of binocular depth cues; an organism must have a binocular visual field -- a region of overlapping visibility for the two eyes. Different animals have different extents of binocular visual fields. In general, predators have both eyes on the front of their heads, and consequently have large binocular visual fields. In contrast, prey typically have one eye on either side of their heads, and consequently have small, if any, binocular visual fields. The visual system uses disparity information as one cue to depth. The fact that a three-dimensional percept can be derived from retinal disparity is seen when we view stereogram displays in which each eye receives a slightly different picture/view.

In the 1830s, Wheatstone developed a device with which to view stereogram: the stereoscope. This device presented one two-dimensional view of a scene to one eye, and a slightly different two-dimensional view to the other eye. When the brain received these slightly different views from the two eyes, it integrated them into one three-dimensional scene. In other words, the disparity between the two scenes enabled the observer to see depth.

Perceptual development means how animals and humans alike develop their seeing capabilities. This development of perception could be learnt or innate. This concept of perceptual development is heavily based from an old issue in psychology, the nature vs. nurture. We have to wonder, stated by Walk in The Development of Depth Perception in Animals and Human Infants, “Do we learn to the world about us, or do we see the world in all its complexity innately, without any learning?” The question of whether individuals learn or inherit the ability to interpret these cues is a persistent controversy among psychologists. Some psychologists maintain that human perceptions of space, at least to a certain extent, are sensed directly by visual cues beginning at birth.

Research involving a visual cliff shows that, by the time infants are crawling, they already avoid tumbling off a visual drop off. Some animals, born with open eyes and walking ability, also