Gregory's Constructivist Theory of Perception (Nurture) (AQA GCSE Psychology)

• Gregory’s constructivist theory of perception is what is known as a constructivist theory as it assumes that perception is the product of learning and experience (of the physical world)
• The theory proposes that past experience and stored information about the world enables human beings to understand what they see, hear, smell etc. 
• The theory claims that humans use their senses to make inferences about the world, particularly when all available information is not known e.g. ‘I can see a curved fin sticking out of the sea which makes me think: shark!’
• Inferences help to fill in the gaps of what the senses are communicating i.e. perception is an active process which helps people go beyond the given information in order to make sense of it
• Gregory & Wallace (1963) conducted a case study of a man (SB) who had been blind since infancy but had his sight restored (he had been blind for 50 years)
  • The researchers tested SB 48 days after his sight had been restored
  • Some of SB’s sight abilities were intact:
    • He walked down a corridor without trouble
    • He enjoyed looking at moving objects
    • He already had some idea as to the size of objects (e.g. the length of a bus)
  • SB did, however, experience some difficulties:
    • He could only focus on objects when specifically asked to do so
    • He had difficulty crossing the road (though this was not the case when he was blind)
    • He had problems understanding depth and distance
  • SB’s depth and distance perception improved over time and with practice
  • It is possible to conclude from these findings that perception may not be completely innate but that particular skills such as depth perception must be learned (i.e. Nurture, rather than nature) 

Gibson & Wallace Blind Man Diagram

Crossing a busy street is made more difficult without good depth perception.

• Gregory & Wallace’s study (1963) described above demonstrates that SB was able to use visual cues to supplement the non-visual cues he had experienced when he was blind e.g. he was not surprised when he saw the length of a bus as he had been on buses when he was blind and had gained a sense of how long they were 
• Visual cues are there to help humans navigate the physical world and to make sense of what they see e.g. a partial view of a banana would not result in someone saying that they were looking at an apple as the two fruits have very different appearances
• Visual illusions can, however, provide faulty clues or information as to what the object is (see the pages here which cover this topic): only one image may be seen, for example in an ambiguous figure
• Gregory used the term ‘mistaken hypothesis’ to explain the errors made by the brain in interpreting visual illusions e.g. by seeing the top bar on a Ponzo illusion as being longer than the lower bar
• Gregory’s theory is a ‘top down’ theory: using inferences to conclude predetermined ideas about the world i.e. people are constantly ‘testing’ their hypotheses about what they can see (and hear/smell/touch/taste)

Top Down vs Bottom Up Processing Diagram

Two different approaches to researching a topic.

Evaluation of Gregory’s constructivist theory of perception

Strengths

• The theory is supported by cross-cultural research which demonstrates that perception may be a product (to some extent) of environment
• The theory explains how illusions such as the Ponzo or the Muller-Lyer work with their emphasis on depth and distance

Weaknesses

• Explaining perception using only the ‘nurture’ argument ignores the fact that babies can use sensory information to make sense of their environment (e.g. Fantz, 1961)
• Gregory & Wallace’s (1963) case study of SB cannot conclusively ‘prove’ that perception is wholly a product of experience as SB did not have to re-learn every aspect of visual perception even after 50 years of blindness