What is perception?
The ability to see, hear or become aware of something through the senses
How is perception an active process?
It is not just the receipt of sensory information
It requires higher order processes such as memory and thought to organise and interpret information
Can 2 individuals have the same perception of an event?
No - an experience can be shared
The perception of this experience is unique to the individual
What are the two directions of processing?
- bottom-up processing
2. top-down processing
How are bottom up processes driven?
What is their function?
They are sensory-driven
They are processes that organise incoming information
When does perception begin in bottom-up processing?
Perception begins with the stimulus itself
In which direction does processing occur when it is bottom-up?
It is carried out in one direction from the retina to the visual cortex
Each successive stage in the visual pathway carries out an increasingly more complex analysis of the input
How are top-down processes driven?
What is their function?
They are driven by knowledge, experience and expectations
They are used to determine perception in ambiguous settings
What does top-down processing refer to?
The use of contextual information in pattern recognition
Why is it easier to understand difficult handwriting when reading complete sentences rather than single words?
The meaning of the surrounding words provides a context to aid understanding
What does top-down processing suggest about perceptions of the world?
perceptions of the world are hypotheses based on past experiences and stored information
What is meant by visual perception?
It describes the brain’s ability to make sense of what the eyes can see
What are adaptation effects in visual perception?
Temporary change in sensitivity or perception when exposed to a new or intense stimulus
What do adaptation effects usually result in?
A negative after-image
What is a negative after-image?
A lingering afterimage that may result when a stimulus is removed
What type of process is depth perception and why?
Top-down process
Life experiences give people an idea about depth
What is binocular disparity?
The difference in image location of an object seen by the left and right eyes, resulting from the horizontal separation of the eyes
How does the brain use binocular disparity?
It uses it to extract depth information from two-dimensional retinal images in stereopsis
What is stereopsis?
the perception of depth produced by the reception in the brain of visual stimuli from both eyes in combination
What is the alternative name for stereopsis and why?
“binocular vision”
binocular cues require use of both eyes to perceive distance and depth
What are monocular cues?
They provide depth information when viewing a scene with one eye
What is an example of a monocular cue?
Linear perspective
When parallel lines appear to converge at some point in the distance
What types of cue are interposition, texture gradients and relative size?
Monocular cues
What does Gestalt or whole percept describe?
How people tend to organise visual elements into groups or visual wholes, rather than the sum of their constituent parts
Why do we use Gestalt or whole percept?
The perceptual system seeks meaningful groupings to make sense of what is being seen
e.g. proximity, similarity, continuity
What is meant by figure-ground organisation?
The ability to distinguish figures from the ground
What do perceptual constancies describe?
The disparity between what the retina receives and what the brain concludes about the image
What is an example of a perceptual constancy involving images showing a door closing?
You know through experience that the shape and size of the door does not change
The perception does not change but the sensory information that is received does change
When do perceptual illusions occur?
When our perception is in error
The brain will bring information into a situation that does not support the sensory information that it is receiving
What is meant by sensory limitations?
The degree to which our sensory processes are aware of what is happening around us
Many things could be occurring that we do not notice
Why do humans have limited sensory ability?
They have adapted to notice only what is essential for survival
How do sensory limitations show protective filtering?
The function of the brain and nervous system protects us from being overwhelmed and confused by a mass of largely useless and irrelevant knowledge
What is the relationship between perception and attention?
We selectively perceive information based on how we adapt our attention
What is selective attention?
It involves screening information
e.g. inattentional blindness and selective listening
What does attentional focus affect?
It involves moving attention away from other things that are going on in the environment
What is the internal model of the physical and social world built up from?
Built up from previous experiences
The brain makes assumptions about objects you see based on prior experience
When a blind person tries to draw a bus, why is it two-dimensional?
They have no way of conveying three-dimensionality
When a blind person tries to draw a bus, which part is missing and why?
Before gaining sight, the blind person built a visual image through touch
They miss out the front of the bus as this is the one area you cannot touch as a passenger
What would a blind person have difficulty in drawing/recognising?
Recognising faces and facial expression
What is the role of context in top-down processing?
The perception of an object can change depending on the context in which you see it
When 8 pseudopatients pretended to be mentally ill, what did they claim to be a symptom?
They are all hearing voices
What happens once they are admitted?
They begin to behave normally
They are looking at how long it takes for medical staff to determine their sanity in a context of madness
What was the outcome?
They were discharged with schizophrenia in remission
