Gibson's Direct Theory of Perception (Nature) (AQA GCSE Psychology)

• Gibson’s direct theory of perception is a theory which claims that perception is based on what a human can see right in front of their eyes
• Gibson claimed that human perception ‘feeds’ off the immediate surroundings in which someone finds themselves
  • There is no need for prior experience or learning to fill in any perceptual gaps
  • Humans start perceiving the world from birth
• The above point makes it clear that Gibson’s theory falls on the side of nature in the Nature (nurture) debate i.e. people are born ready to perceive their world (in this regard Gibson did not distinguish between sensation and perception)
• Gibson & Walk (1960) conducted a groundbreaking study in which they demonstrated their theory that very young infants show evidence of innate depth perception as follows:
  • The researchers built a structure which was designed so that if a baby crawled on a raised glass top they would see the ground suddenly drop away from them (see the image below):
  • The baby would be able to see that the ground beneath them appeared to have disappeared when in fact it was covered in the glass sheet and was safe to cross
  • The researchers hypothesised that each baby would stop at the ‘edge’ of the patterned table top and would refuse to continue across the transparent glass - even when their mother was standing at the other side of the table encouraging them to move forward
  • 92% of the babies stopped at the ‘edge’ and refused to cross the transparent glass tabletop
  • The researchers concluded that this was evidence that humans are born with depth perception as very young babies cannot have learned an aversion for sheer drops or steep edges

Gibson & Walk Cliff Walk Diagram

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

• Motion parallax describes what happens when a human moves through a space (not outer-space)
  • Either on foot, by bicycle, car, train etc.
• Moving through a space involves the sensation that objects are coming towards the person as they pass them while at the same time the destination point remains stationary e.g. ‘All the houses in my street pass before me in the opposite direction as I drive towards the park at the end of my road’
• What is described above is a form of visual streaming: continuous movement in one direction means that the retina is being continuously stimulated by changing images which tell the brain ‘I am in motion’: in other words - optic flow
• Motion parallax involves the cues the brain receives from optical flow and transmits them in the following ways:
  • Objects closest in the visual field appear to be moving faster than objects which are further away in the visual field
  • Objects which are close to mid-range in the visual field move in the opposite direction to the person
  • In contrast, objects further away from the visual field move in the same direction as the person who is moving (test this the next time you are in a car or a train - as long as you’re not driving!)

Motion Parallax Diagram

Motion parallax can be observed in a moving vehicle such as a train.

• Gibson’s theory applies very well to the experience of pilots - particularly during the crucial minutes they spend landing the plane (in fact he developed his theory using actual pilots during the Second World War)
• Optical flow is used by pilots to provide them with information about:
  • the distance between the plane and the ground
  • any obstacles they might need to factor in
  • the landing surface
  • the speed and deceleration of the approach
  • the outline of the runway
• Gibson claimed that all of the above is sufficient to land a plane, determined by the patterns made by the light hitting the retina of the pilot

Gibson's Optical Flow Diagram 

An example of a pilot’s optic flow. 

Evaluation of Gibson’s direct theory of perception

Strengths

• The theory has been used (see above) to train pilots so it has good validity
• Gibson & Walk’s (1960) study shows good support for the idea that perception is innate as young babies cannot ‘fake’ their response in an experiment i.e. the study has validity

Weaknesses

• Gibson’s theory cannot explain visual illusions as these are examples of our eyes (and brain) playing ‘tricks’ on our perception of what we see in front of us
• Any research using very young babies is bound to have some issues:
  • Babies cannot explain why they behaved the way they did in the experiment;
  • Babies tend to be unpredictable;
  • There are ethical concerns with a procedure such as The Cliff Walk i.e. harming the child