Visual Perception Flashcards
Perception
The process of organising and interpreting sensory information in a meaningful way
Sensation
The process by which our sense organs and receptors detect and respond to sensory information that stimulates them
Visual perception system
The complete network of physiological structures involved in vision
Visual processing model
- reception
- transduction
- transmission
- organisation and interpretation
Reception
The process by which the eye receives incoming lights by focusing it onto the retina where an image of the visual stimulus is captured
Transduction
Photoreceptors convert electromagnetic energy to electrochemical energy (electrical impulses)
Transmission
Send electrical impulses along the optic nerve to the brain (visual cortex)
Organisation and interpretation
Organisation: arranging the features of a visual image in a meaningful way
Interpretation: assigning meaning to visual information
Cornea
A transparent, convex-shaped covering which protects the eye and helps focus light rays onto the retina
Pupil
An opening in the iris that helps control the amount of light entering the eye
Iris
The coloured part of the eye consisting of a ring of muscles that expand or contract to change the size of the pupil and control the amount of light entering the eye
Photoreceptor
A light-sensitive visual receptor cell in the retina at the back of the eye
Rods
Photoreceptors in the retina that respond to very low levels of light and are primarily responsible for night vision
Cones
Photoreceptors in the retina that respond to high levels of light and are primarily responsible for vision in well-lit conditions, colour vision and detecting fine details
Ciliary muscles
Muscles attached to each end of the lens that changes it’s shape
Lens
A transparent, flexible eye structure located immediately behind the pupil which plays a major role in focusing light onto the retina
Retina
Layer of neural tissue at the back of the eye that receives and absorbs light, and processes images for transmission to the brain
Optic nerve
A connecting nerve that’s ends visual information from the eye to the visual cortex in the brain
Visual perception principle
A ‘rule’ that is applied to visual information to assist in organisation and interpretation of the information in a consistent and meaningful way
Gestalt principle of visual perception
Organising the features of a visual scene to perceive a whole, complete form. Includes: - figure-ground - closure - similarity - proximity
Figure-ground
Organising visual information by perceptually dividing a visual scene into a ‘figure’, which stands out from the ‘ground’, which is it’s surroundings
Closure
The perception all tendency to mentally ‘close’, fill in or ignore gaps in a visual image and to perceive objects as complete
Similarity
Involves the tendency to perceive parts of a visual image that have similar features, such as size, shape, texture or colour, as belonging together in a unit, group or ‘whole’
Proximity
The perceptual tendency to perceive parts of a visual image which are positioned close together as belonging together in a group
Depth Perception
The ability to accurately estimate the distance of objects and therefore perceive the world in 3 dimensions
Depth cues
Sources of information from the environment or from within our body that help us to perceive how far away objects are and therefore perceive depth
Types of depth cues
- monocular
- binocular
Binocular depth cues
Require the use of both eyes working together in order to provide information to the brain about depth and distance
Types of binocular depth cues
- convergence
- retinal disparity
Convergence
Involves the brain detecting and interpreting depth or distance from changes in tension in the eye muscle that occur when the two eyes turn inwards to focus on objects that are close
Retinal disparity
The very slight difference in the location of the visual images on the retina (due to their slightly different angles of view) which enable us to make judgements about the depth or distance of an object
Monocular depth cues
Require the use of only one eye to provide information to the brain about depth and distance, but they also operate with both eyes
Types of monocular depth cues
- accommodation (primary monocular cues)
- pictorial cues (secondary monocular cues)
Accommodation
Involves the automatic adjustment of the shape of the lens to focus an object in response to changes in how far away the object is
Pictorial cues
Artists use them to create depth and distance on 2 dimensional surfaces
Types of pictorial cues
- linear perspective
- interposition
- texture gradient
- height in the visual field
- relative size
Linear perspective
The apparent convergence of parallel lines as they recede into the distance
Interposition
Occurs when one object partially blocks or covers another, and the partially blocked object is perceived as further away than the object that obscures it
Texture gradient
Gradual reduction of detail that occurs in surface as it recedes into the distance, compared with a surface that is close and perceived in fine detail
Relative size
The tendency to visually perceive the object that produces the largest image on the retina as being closer, and the object that produces the smallest image on the retina as being further away
Height in the visual field
The location of objects on our field of vision; the objects that are closer to the horizon are perceived as further away
Perceptual constancy
Refers to the tendency to perceive an object as remaining stable and un hanging despite any changes that may occur to e image cast on the retina
Types of constancy
- size
- shape
- brightness
Size constancy
Involves recognising that an objects actual size remains the same, even though the size of the image it casts on the retina changes
Shape constancy
The tendency to perceive an object a maintaining its shape despite any change in shape of the image of the object on the retina
Brightness constancy
The tendency to perceive an object as maintaining its level of brightness in relation to its surroundings despite changes in the amount of light being reflected from the object to the retina
Physiological factors
Involve the ways in which our eyes, nervous system and brain process visual information
Psychological factors
Involve mental processes such as our past experiences, socio-cultural background, memory, thinking, language, motivation and emotions
Perceptual set
The predisposition (or readiness) to perceive something in accordance with what we expect it to be
Things that affect our perceptual set
- context
- motivation
- emotional state
- culture
- past experience
Context
The setting or environment in which a perception is made. When organising and interpreting information, we take account of the setting and pay more attention to those aspects of the setting that are immediately relevant
Motivation
Refers to he processes within us which activate behaviour that is directed towards achieving a particular goal
Emotional state
How we are feeling can influence the way in which we perceive visual information. Different emotions can ‘set’ us to perceive information in a particular way which is consistent with the emotion being experienced
Past experience
Our personal experiences throughout our lives. This includes everything we learn through experience, both intentionally and unintentionally
Culture
The way of life of a particular community or group that sets it apart from other communities or groups
Visual illusion
A misinterpretation or real sensory information. An experience in which there is a mismatch between our perception and what we understand as physical reality
Müller-Lyer illusion
A visual illusion in which one of two lines of equal length, each of which has opposite shaped ends,is incorrectly perceived as being longer than the other
Müller-Lyer illusion
Biological perspective
Eye movement theory:
Arrowheads and feather-tailed lines require different types and/or amounts of eye movements to perceive the lines
Müller-Lyer illusion
Behavioural perspective
Learning and past experience:
illusion contradicts what we haves learned throughout life about physical reality
Carpentered world hypothesis:
Occurs because of its similarity to familiar architectural feature in the real world we experience in everyday life
Müller-Lyer illusion
Socio-cultural perspective
Learning and past experience:
People in a ‘non-carpentered’ world who haven’t been exposed to rectangular structures as much are less likely to perceive the illusion than people in a ‘carpentered’ world
Müller-Lyer illusion
Cognitive perspective
Incorrect use of size constancy:
We assume to smaller line is further away than what it actually is due to our incorrect use if size constancy which causes us to interpret that when two lines appear to be at different distances and cast retinal images of equal size, then the line which appears to be further away must be longer
Ames room illusion
An illusion which involves a trapezium-shaped room that is longer and higher on one side than the other. When viewed through a peephole at the front of the room using only one eye, the room appears rectangular
