Psychology Topic 2 - Visual perception

Yr 12 Unit 3 IA1 DATA TEST QLD

Absolute threshold

the min stimulation needed to detect a particular stimulus 50% of the time

Reception

the stimulus energy is collected by the sense organ

transduction

stimulus energy is converted by the receptor cells into electrochemical nerve impulses

transmission

the sending of neural signals to the primary sensory cortex when the specialized receptor cells respond as the process of perception begins

selection

the process of selecting the important sensory info on which to focus attention from the millions of stimuli we receive

organization

sensory info reaches the brain and is reorganized so we can make sense of it

interpretation

stimulus is given meaning in the brain based on our past experiences, motives, values and context

sensation

the process by which our sensory receptors and the nervous system receive and represent stimulus energies from our environment and transmit it to the brain

photoreceptors

a layer of specialized nerve cells that detects the visual stimuli, the make up the retina and convert visual light energy into nerve impulses

rods

photoreceptors that become active under low-light conditions for night vision

cones

photoreceptors connected near the center of the retina that function in daylight or well-lit conditions. These detect fine detail and give rise to colour sensations

optic nerve

the two tracts of neurons that transmit visual info form the eyes to the occipital lobes

receptive field

a particular region of the visual space

retinal ganglion cell

a type of neuron that is located near the surface of the retina; receives visual info form the photoreceptors

visual acuity

clarity/clearness of vision

perception

the process whereby the brain organises and interprets sensory info

feature detectors

cells in the optic nerve that individually respond to lines of a certain length, angle or direction to break up an image for visual perception

light energy

the visible part of the electromagnetic spectrum

presbyopia

farsightedness caused by loss of elasticity of the lense of the eye, occurring typically in the middle and old age

floaters

clumps of matter that appear as small specks of spots in central vision

cataracts

cloudy spots in the lens that cause vision to become blurred when proteins in the lens break down

glaucoma

a disease affecting the optic nerve that interferes with the transmission of peripheral visual info to the brain

age-related macular degeneration

a build up of grainy deposits in the center of the retina causing deterioration of central vision

inherited visual disorders

visual disorders passed down from parents to children due to genetic factors

congenital visual disorders

visual disorders present at birth

colour vision deficiency

a genetically inherited disorder affecting how people perceive colour

retinis pigmentosa

a genetic degenerative disease affecting the retina

perceptual set

a predisposition/readiness to perceive something in a particular way

perceptual constancies

allow us to recognise familiar stimuli under varying conditions

size constancy

the tendency to interpret an object as always being the same actual size, regardless of its distance

shape constancy

the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina

Gestalt principles of visual perception

used to organise and interpret perceptual stimuli; including figure-ground organisation, closure, similarity and proximity

figure-ground organisation

Gestalt principle where images are organised into the central object of attention (figure) and a background (ground)

camouflage

the contour of the figure is blended against the ground, making it more difficult to see

closure

when an object is perceived as being whole despite actually being incomplete

similarity

the principle that elements that are similar in appearance will tend to be seen as a unit

depth perception

the ability to accurately judge 3D space and distance, using cues in the environment

proximity

the individual parts of a stimulus patter are close together, allowing those parts to be perceived visually as a whole

binocular depth cues

depth cues that use both eyes to gauge distance and space

monocular depth cues

depth cues that use one eye independently or both eyes together to gauge distance and space

retinal disparity

the binocular depth cues that arises as the brain compares and contrasts the 2 slightly different distance between the two eyes

convergence

a binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object

accommodation

the process by which the eye’s lens changes shape to focus near or far objects on the retina

pictorial depth cues

a monocular depth cue used by artists to create a 3D perception of something that exists on a 2D suface

linear perspective

a monocular depth cue that parallel lines appear to converge as they retreat into the distance

interposition

a monocular depth cue, in which objects further form the observer are partially obscured by those in the foreground

texture gradient

a monocular depth cue in which texture in the foreground is seen in finer detail than that further away

relative size

a monocular depth cue based on our tendency to perceive the object producing the largest retinal image as being the nearest and the object producing the smallest retinal image as being the furthest.

height in the visual field

a monocular depth cue that shows depth by portraying objects further away as being closer to the horizon

Sensation - Perception Acronym

Real (Reception) Alphabetical order (Transmission, Transduction), Special (Selection), Orange (Organization) Ice blocks (Interpretation)

Reception

stimulus is recognized by photoreceptors

Transduction

Stimulus info is processed by receptive fields

Transmission

Optic nerve carries info to the occipital lobe

Selection

Feature detectors focus on particular elements of the stimulus to determine what is and is not attached to.

Organisation

use visual cues to interpret details, which are then passed to temporal lobe for identification and the partial lobe for judgment (location of the stimulus in space)

interpretation

temporal lobe applies meanings to the stimulus based on memories and stored info

electromagnetic spectrum wavelength visible to humans

360-720/40

Social influences on perception

cultural norms and expectations influence how we interpret images. Cross-cultural research (Deregowski 1972) showed that some African tribes were unable to recognise 3D depth cues in human face photos or could not see pictorial clues to estimate depth and distance (relative size and height in the visual field). 

Hudson Study

studied Bantu warriors from different tribal backgrounds, educational levels and degrees of urbanisation.  All participants were shown 14 unambiguous pictures. Hudson found that there was a difference between 2D and 3D perception between African tribal members and the general population.

visual illusion

occurs when perception consistency differs from objective reality

Pronzo illusion

upper horizontal lines in a series of diagrams are perceived to be longer than the lower horizontal lines because we mistakenly perceive depth cues of linear perspective and heigh in the visual field

muller-lyer illuison

consists of 2 lines of = length with regular arrowheads on one end and inverted on the other. We percive the line with inverted arrow heads as being longer than the regular arrow headed line due to the Carpentered World Theory

impossible figures

work by exploiting perceptual cues so that we are forced to see images that should not be possible or should not be able to exist

ambiguous figures

examples of optical illusions that work by exploiting similarities int he image, and aspects of the way our visual system interprets between two or more objects in an image

optical illusions

physical properties of light