Gibson's Direct theory of Perception (nature) (AQA GCSE Psychology): Revision Note

Sufficient information for direct perception

• Gibson's direct theory claims perception happens directly from the information in the environment – no interpretation is needed

• Gibson did not distinguish between sensation and perception

  • What the senses detect is what we perceive, so there is no separate stage where the brain interprets the data

• The optic array is all the light reaching the eye from the environment; it is so rich in information that the brain does not need to fill in gaps using past experience

• Cues in the optic array include:

  • optic flow (the view rushes past at the edges as we move forward)

  • motion parallax (near objects appear to move faster than far ones)

  • texture gradient (surfaces look denser as they get further away)

• Gibson argued that perception is innate

  • We are born able to perceive; it does not have to be learned

• This is a bottom-up theory, driven by sensory data, and the opposite of Gregory's constructivist theory, which says perception is built from past experience

Gibson & Walk (1960)

• Gibson & Walk tested whether depth perception is innate using a visual cliff

  • The cliff was a glass-topped table with a checkerboard pattern directly under the glass on the 'shallow' side and several feet below it on the 'deep' side, so that the deep side looked like a drop but was safe to crawl on

• 36 infants aged 6–14 months were placed on a centre board and their mothers called them from the shallow side and then the deep side

• Of the 27 babies who moved, all crawled onto the shallow side but only 3 crawled onto the deep side; most refused the deep side even when their mother called, and some cried

• Gibson & Walk concluded that infants can perceive depth by the time they can crawl, supporting the view that depth perception is innate – the texture gradient under the glass gave the babies enough information to perceive the drop directly

• However, the babies were 6–14 months old and had experience of the world, so they may have learned depth perception

Gibson & Walk’s (1960) ‘cliff walk’ structure.

Motion parallax & everyday perception

• Motion parallax is a monocular depth cue that occurs when the observer is moving, e.g. on foot, by bike, in a car or train

• Objects at different distances appear to move at different speeds and in different directions:

  • Near objects appear to move fast and in the opposite direction to the observer, e.g. fence posts flashing past a train window

  • Distant objects appear to move slowly and in the same direction as the observer, e.g. hills on the horizon seeming to travel with the train

• The brain uses this difference in apparent speed to judge which objects are near and which are far, directly from the optic array – no past experience needed

Motion parallax from a moving train: near objects rush past, distant objects barely move.

Optic flow

• Optic flow is a related but separate cue: as we move forward, the whole visual scene appears to flow outwards from the point we are heading towards

  • The destination point stays still; everything else streams past towards the edges of the visual field

  • The faster the flow, the faster we are moving – so optic flow tells us directly about our own speed and direction

• Gibson developed these ideas while training pilots in the Second World War

• When landing, optic flow gives the pilot direct information about the plane's speed, its angle of approach and its distance from the runway – the point of the runway the plane is heading towards stays still while the ground streams past either side

• Gibson argued this shows the optic array contains enough information for accurate perception without the brain having to interpret it

Optic flow as seen by a pilot landing: the scene streams outwards from the point the plane is heading towards.

Evaluation of Gibson’s direct theory of perception

Strengths

• Real-world application: Gibson's work with pilots shows the theory explains perception in real, moving environments and has been used in pilot training

• High ecological validity: unlike research based on 2D illusions in a lab, Gibson studied how people perceive while moving through real 3D environments, which is how perception normally operates

• Supporting evidence: Gibson & Walk's (1960) visual cliff study found that most babies would not crawl over an apparent drop, supporting the claim that depth perception is innate

Weaknesses

• Cannot easily explain visual illusions: if perception were direct and accurate, illusions such as the Müller-Lyer should not occur; the fact that they do suggests the brain is interpreting information, as Gregory argued

• Evidence that experience matters: Hudson (1960) found that people from cultures with little exposure to pictures interpreted depth cues in drawings differently, suggesting perception is at least partly learned (nurture), which the direct theory cannot explain

• Research with babies has limitations: they cannot explain their behaviour, so researchers have to infer what the baby perceived from whether it crawled or not