Visual Perception Flashcards

perceptionthe selection, organisation

and interpretation of visual sensations into meaningful

events and objects.

FROM THE EYE TO THE BRAIN

Neural impulses leave the retina via the optic nerve and travel to the occipital lobe in

the brain.

TURNING LIGHT INTO SIGHT

Sensory receptors convert stimulus energy into impulses of electrochemical energy for

neural activity.

TAKING LIGHT IN Sensory receptors detect the

presence of a stimulus Light enters the eye through the

cornea, passing through the pupil. The lens focuses the light on the

retina which receives the figure.

RECEPTIONSTAGE 1 of the visual perception

process

transmissionSTAGE 3 of the visual perception

process

TRANSDUCTIONSTAGE 2 of the visual perception

process

FEATURE DETECTORS AT WORK

The process of feature detector cells responding to specific features of a

stimulus pattern.

selectionSTAGE 4 of the visual perception

process

organisationSTAGE 5 of the visual perception

process

Reassembling the features of sensory stimuli in a meaningful

manner. Image travels to the TEMPORAL

LOBE for identification and the PARIETAL LOBE to judge where

the object is in space.

INTERPRETATIONSTAGE 5 of the visual perception

process

The process of assigning meaning to

sensory stimuli so that it can be understood.

feature detector cells Neurons specialised to respond to specific perceptual features of a

stimulus pattern in visual perception.

Respond to basic visual features such as lines,shapes,edges,spots

and colours.

lobes of the brainFRONTAL LOBE

Planning,reasoning,emotions/personality.

PARIETAL LOBESpacial reasoning, sensory information.

OCCIPITAL LOBE Visual perception

TEMPORAL LOBE Memory, auditory perception.

the eye

sensation A psychological process involving

sensory receptors detecting and responding to the presence of a

stimuli.

PERCEPTION & SENSATIONSensation refers to the process of sensing our

environment through touch,taste,sight,sound and smell. Perception is the way we interpret these

sensations and therefore make sense of everything around us,

IRIS: A coloured, circular muscle inside the eye that expands and contracts to change the size of the pupil.PUPIL: An adjustable opening in the centre of the eyes iris through which light enters; appears as blackLENS: A transparent,convex structure behind the iris that changes shape to focus light into an image on the retina.RETINA: A light-sensitive membrane composed of a number of layers of specialised neurons at the back of the eye.FOVEA: A small,cup-shaped area in the middle of the retina containing only cones.CILIARY MUSCLES: Muscles attached to each end of the lens that contract or relax to change the shape of the lens so it can focus light images of objects at varying distances.CORNEA: Transparent, convex-shaped membrane that protects the front part of the eye.BLIND SPOT: The opening in the retina through which the optic nerve exists to the brain.

the electromagnetic spectrum The full range of electric and magnetic wavelengths that exist in the external environment.

VISIBLE LIGHT SPECTRUM380 (purple/violet)-750(red) nanometres.

(Beyond this,human eyes are unable respond to infrared and ultraviolet light)

rodsKEYWORDS

Visual Acuity: Sharpness of vision and ability to detect fine detail.

Photoreceptors: Receptor cells located at the back of the retina and specialised to detect and respond to light.

Located mainly on the outer edges of the retina.

Approx.100 million in each retina. Low visual acuity. Functions best in dim light. Black & White vision Responsible for PERIPHERAL VISION

and for DETECTING MOVEMENT.

conesKEYWORDS

Visual Acuity: Sharpness of vision and ability to detect fine detail.

Photoreceptors: Receptor cells located at the back of the retina and specialised to detect and respond to light.

Mainly in the centre of the retina (fovea)

Approx.6.5 million in each retina. High visual acuity. Functions best in bright light. Colour vision

visualthresholds

THRESHOLD Refers to the level of which a stimulus is strong

enough to trigger a neural response in a sense organs sensory acceptors.

ABSOLUTE THRESHOLD Minimum amount of light energy necessary for the

perception of a visual stimulus. DIFFERENTIAL THRESHOLD

Just notice-able difference. Minimum difference that a person can perceive

between the intensity of two visual stimuli.

gestalt principles

(Figure-ground,closure,similarity,proximity)

A group of principles that organise visual perceptual features and that integrate

them into connected pattern or whole forms.

figure-ground Figure: the part of the visual field that is being attended to. The ground: the surrounds.

Figure and ground are separated by an imaginary contour, there is a distinct

difference between the figure and the background.

closure Perceiving an image as being whole despite it actually being incomplete.

The viewer has a tendency to complete a figure by filling in an

imaginary contour line so that the figure has a consistent overall form.

similarity When an individual has the tendency to perceive stimuli that

with similar visual features as belonging together

(shape,colour,line,form)

proximity Stimuli close together are perceived as belonging together and forming a meaningful single unit or

group.

depth perception principles

(adding a third dimension)

The ability to add 3D (height,length,width) from 2D images on our retina.

binocular and

monocularcues

BINOCULARRequire both eyes to work together to provide the brain with information about depth and distance.

MONOCULARRequire information from one eye only.

RETINAL DISPARITY

(BINOCULAR DEPTH CUE)

Small discrepancies between an image that reaches the right eye and the other

that reaches the left eye, each retina receives slightly different images.

Disparity between the images are picked up in the OCCIPITAL and PARIETAL

lobes.

(used to make 3D movies)

convergence(BINOCULAR DEPTH CUE)

Involves both eyes simultaneously turning inwards as an object moves closer in

order to maintain focus. Controlled by a group of muscle which

contract/relax, feeding information to the brain to judge distance.

DISTANT: eyeballs are parallelCLOSE: eyes will turn inwards.

accomModation(MONOCULAR DEPTH CUE)

Ciliary muscles contract/relax altering the shape of the lens in each eyes to focus

an object at varying distances. Judges distances within a range of

20cm to 3m.

DISTANT: lens flatten to focusCLOSE: lens bulge to focus

linear perspective

(MONOCULAR DEPTH CUE)

(PICTORIAL CUE create the impression of depth where depth does not exist, creating 3D out of 2D)

The apparent convergence of parallel lines creating the impression of

increasing distance.

relative size



Involves two similar objects in the one image.

The SMALLER image appears FURTHER AWAY.

The LARGER of the image appears to be CLOSER.

interposition (MONOCULAR DEPTH CUE)


Occurs when one object partially blocks another object and is perceived as being in front of and therefore closer than the

object it covers.

texture gradient



The surface features of an object become smaller and less detailed the

more distant an object becomes.

height in the visual field



The height of objects in the visual field (either above or below the horizon) act as a

depth cue. CLOSE to the horizon: appear further away BELOW the horizon: appear closer

visual constancies

Perception principles that enable an individual to maintain stable perception of a stimulus (unchanging in terms of actual size,shape brightness and

orientation)

orientational constancy

Perceiving an objects true orientation as being unchanged despite changes in the orientation of the objects image on

the retina.

Example: When watching TV, the subjects view of the television maintains orientation constancy despite facing the TV differently. (Image still appears upright)

shapeconstancy

An object is perceived to maintain its known shape despite the changing

perspective from which it is observed.Example: As a door opens towards us the shape of the shape of the image of the door changes. Rather

than perceiving the door as changing shape, we perceive that its shape remains constant and its

position as changing.

sizeconstancy

Maintaining a constant perception of an objects size even though the size of the image on the retina alters as the object

moves nearer or further away.

Example: Moving an apple closer towards you. The perceives size of the apple is the same even though the size of the image becomes larger on the retina.

Perceptual constancy whereby an objects perceived level of brightness relative to its surroundings stays the

same despite changing light conditions.Example: A piece of paper physically doesnt change

in colour under different light conditions instead its appearance does,due to the level of brightness

being reflected onto the retina.

brightnessconstancy

perceptual set

A readiness or predisposition to perceive visual stimuli in a particular way according to our expectations. Psychological factors that influence the was we

perceive stimuli. These can be externally or internally effected.

effect of past experience

Prior exposure to stimuli and previous life experiences.

The tendency to interpret new stimuli the same way an individual has interpreted similar stimuli in

the past.

Example: Reading a magazine and failing to notice a spelling error in a word- you perceive the word as

being correct.Paris

in the the spring.

context The environment or setting in which a

perceived event/object exists. Provides a framework to the serve the observer circumstances and conditions which

surround it.

Example:

effect of motivation

MOTIVATION Internal state that activates, directions

and sustains behaviour in relation to achieving a specific goal. Motives can be influenced by psychological factors e.g interests,ambitions and desires.

Example: We see what we want to see, rather than what is actually there.

We expect to see a letter in the context of other letters of the alphabet,where as we expect to see numbers in the context of other numbers

EMOTIONAL STATEHow an individual is feeling.

Example: A child who is afraid of being in their darkened bedroom may interpret the shadow of their dressing gown hanging on their door as a ghost.

EFFECT OF EMOTIONAL

STATE

effect of culture

The patterns of behaviour,values and beliefs shared by a group.

Example:What do you see?Which is nearer, the antelope or the elephant?What is the man doing?' (Noted difficult among South African tribes in interpreting depth cues in pictures.

effect of suggestion or

instruction

Suggestions given by others or by instructions we are given before attempting to do something which can influence of perceptual set.

Example: Seeing a newborn baby dressed in blue or pink which suggests the gender of the baby due to sex stereotypical colours.

A visual illusion in which two lines of equal length one capped with inward-pointing arrowheads, the other capped with outward-pointing arrowheads are perceived as being of different lengths.

MllerLyer illusion

An illusion caused by an intentionally distorted room, viewed through a peephole, disrupting perceptual constancies and misleading the viewer to perceive people changing size (shrinking or growing) as they cross the floor from one corner of the room to the corner diagonally opposite.

ames room

ponzo ILLUSIONAn illusion where two horizontal lines of equal length are drawn inside two converging lines, but the line in the narrower section of the converging lines is perceived to be longer.

example of a operational hypothesis

It is hypothesised that adolescent males who sleep for less than six hours a night will be more likely to to have lower memory abilities,as measured by scores on a comprehension test, than adolescent males who sleep for six or more hours a night.

POPULATION PREDICTIONHOW VARIABLES ARE MANIPULATED (OPERATIONALISED IV)HOW THE VARIABLES ARE MEASURE (OPERATIONALISED DV)

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Visual Perception Flashcards