Gregorys top down theory of perceptual organisation

Perception is not based on stimulus patterns; rather it is a dynamic searching for the best interpretation of the available data

Perception involves going beyond the immediately given information 

Perception is an active process whereby our past experiences, context, knowledge, expectations and motivations can affect the visual information we receive.

A perceived object is a hypothesis- makes the best guess about what the object is/ test it against the evidence of our eyes

Process takes place very rapidly - sometimes our senses present us with ambiguous data/ process of perception is slowed down

Perceptual set

Visual illusions

Bias^ reediness to perceive some things in terms of others/ brain is pushed^ set in to perceiving things in certain ways due to factors such as past experience context, motivation

Fits in with the idea that perception is influenced by experience/ guess work

Miturn/ Bruner

Middle figure more likely to be seen as a number 13 when presented with 12 and 14

B when presented with A and C

Support a top down approach / suggest that perception Is not just influenced by the sensory data but by the persons interpretation of the data due to experience, context  

Gregory believed that the brain creates a hypothesis to explain the sensory data

Visual illusions demonstrate how we can be misled and draw the wrong conclusions about what we see. Many illusion arise from our tendency to perceive 3D objects from 2D drawings 

Two horizontal lines are equal in length/ top one is perceived as being longer due to the covering lines eliciting a perception of depth

How dose Gregory explain the illusion

We see this as a 3D object with the top line further away then the bottom line. As things further away appear smaller they are (size constancy) brain interprets the top line as being longer 

Top down theory is very comprehensive- shows how perception is influenced by a number of cognitive, environmental, emotional and motivational factors

Gregory’s theory also offers an explanation for why people perceive  things differently from each other 

Many studies criticised for lacking validity- visual illusions involve very artificial 2D stimuli that give very little information about depth and context

Eysenck believes there are two visual systems: vision for perception and vision for action

Gregory’s theory more relevant to the VFP system- ignores movement