The Gibsonian Approach to Direct Perception.
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The Gibsonian Approach to Direct Perception There are 2 fundamentally opposing theoretical approaches to understanding perception, incorporating (1) the traditional constructivist paradigm and (2) the ecological paradigm. The constructivist perspective, proposed mainly by Helmholtz, Gregory and Rock, holds that perception is essentially a construction of the mind, and is therefore indirect. That is that in between the optical input and our perception of it, are intervening psychological processes involving mental elaboration. They believe that sensory inputs are not sufficient to mediate perception alone and that something must be added to it before the final perceptual response it achieved. Ecological theorists, on the other hand, and specifically Gibson (1950, 1966, 1979) developed a theory of direct perception that has completely rejected this scientific dogma by showing that perception was not based on sensory inputs or stimuli at all. Instead he claimed that perception was based on ecological information, which is external to the organism. The following essay will highlight the fundamental key components of this revolutionary theory in order to explain why this theory is so radical. Instead of concentrating on the information-processing going on within individuals as they see, Gibson examined the information that was available to the organism from its environment.
There are two distinct forms of invariants commonly known to the theorists as transformational and structural invariants. Transformational invariants disclose information about what is happening to any object. They are consistent patterns of change (such as the rule mentioned before that when an object comes closer and closer to the eye it appears proportionally larger. If this rule cannot be applied then either the speed of movement or the actual size of the object has changed. Another example of a transformational invariant is when a rectangle is tilted away from us its projection shape becomes trapezoidal but continues to look rectangular. The trapezoid is a transformation of the rectangle but there must be something invariant in the shape that allows the observer to perceive it as a tilted rectangle. Structural invariants also play a vital part in direct perception. According to Gordon (1997) they are higher-order patterns or relationships, which remain constant despite changes in stimulation. A relevant example is how we perceive two objects of equal size at different distances from the observer to be in fact the same size. Gibson's answer reflects the importance of the horizon explaining that the ratio of an objects height to the distance between its base and the horizon is invariant across all distances from the viewer (Gordon, 1997).
Therefore, from this brief description of the major concepts that typify the ecological approach it is clear that this theory is truly radical indeed. The tenets underlying this theory stand apart from any of the mainstream perceptual theories that have been previously proposed, not only on a psychological level but almost on a philosophical level also. Gibson's theory rests on the concept of 'ecological optics' which he established as a completely new branch of optics, distinct from the traditional optics found in physics. Moreover, his fundamental concept of the 'optic array' (an alternative to the concept of 'retinal image') and optical flow field are unique and offer a radically different approach as to how we might construe the stimulus for vision. It is clear therefore why Gibsonian's are typically so evangelical about the merits of the ecological approach as the ideas are so new and fresh and completely different to any ideas that have previously been put forward. Furthermore, Gibson's emphasis on ecological components have greatly influenced a number of theorists and has helped the study of perception to shift from laboratory created experiments into external environment analyses. His approach is therefore more ecologically valid than the constructivist paradigm as he examines organisms in their natural external habitat. In conclusion therefore, Gibson's pioneering ecological theory has significantly helped to advance the academic study of perception and remains one of the most powerful and influential perceptual theories to date.
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