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Gibson’s Bottom-Up Theory of Perception

Gibson’s Bottom-Up Theory:

  • Gibson argues that there is enough information in our environment to make sense of the world in a direct way.
  • For Gibson: sensation is perception: what you see if what you get.  There is no need for processing (interpretation) as the information we receive about size, shape and distance etc. is sufficiently detailed for us to interact directly with the environment.
  • Gibson talks about movement in his theory; As we move through our environment, objects which are close to us pass us by faster than those further away.
  • He worked during World War II on problems of pilot selection and testing and came to realize: In his early work on aviation he discovered what he called ‘optic flow patterns’. When pilots approach a landing strip the point towards which the pilot is moving appears motionless, with the rest of the visual environment apparently moving away from that point.

The outflow of the optic array in a landing glide.

Evidence to Support Gibson’s Theory:

1. ‘Light and the Environment – Optic Flow Patterns’

  • Changes in the flow of the optic array contains important information about what type of movement is taking place. For example any flow in the optic array means that the person is moving, if there is no flow the person is static.
  • Gibson claims that the center of that movement indicates the direction in which the perceiver is moving.

The Optic Flow pattern for a person looking out of the back of a train.

2. ‘The Role of Invariants in Perception’

  • Gibson notes that we rarely see a static view of an object or scene. When we move our head and eyes or walk around our environment, things move in and out of our viewing fields. Textures expand as you approach an object and contract as you move away. There is a pattern or structure available in such texture gradients which provides a source of information about the environment.it always occurs in the same way as we move around our environment and, according to Gibson, is an important direct cue to depth.
  • Two good examples of invariants are texture and linear perspective:

3. ‘Affordances’

  • Affordances are cues in the environment that aid perception. Important cues in the environment include:

                – Optical Array – The patterns of light that reach the eye from the environment.

                – Relative Brightness – Objects with brighter, clearer images are perceived as close.

                – Texture Gradient – The grain of texture gets smaller as the object recedes.

                – Relative Size – When an object moves further away from the eye the image gets smaller.

                – Superimposition – If the image of one object blocks the image of another, the first object is seen as closer.

                – Height In The Visual Field – Objects further away are generally higher in the visual field.

 

Evidence against Gibson’s Theory:

1. Gibson’s theory of perception provides an explanation for fast accurate perception, however he fails to explain why perceptions are sometimes incorrect.

2. Gibson’s theory fails to explain naturally occuring ‘illusions’.

3. One of the weakest aspects of Gibson’s theory is the concept of affordances. Humans live within a particular cultural context in which knowledge about the use of objects is learned rather than ‘afforded’.

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