Unit 3 Topic 2 Flashcards
Visual Perception
Reception
- stimulus energy is collected by the eye
Transduction
- receptor cells in the eye convert stimulus energy into nerve
impulses, transformed light energy travels along the optic
nerve
Transmission
- these nerve impulses are sent to the brain’s sensory cortex -
perception begins
Selection
- focus on most important sensory information, selecting info for
attention, feature detectors select what our attention focus on
Organisation
- reorganising the info so that it makes sense, perceptual
constancies, gestalt principles, depth cues - sends to temporal
lobe to identify + parietal lobe to judge where object is in space
Interpretation
- past experiences, values, motives, and context give meaning to
the stimulus
Visual mechanisms
sensation - sensory organs/receptors recieve sensory information and transmit it to the brain
reception
- light enters through the cornea
- passes through the pupil
- the lens then focuses the incoming light onto the retina
- retina contains photoreceptors (rods + cones)
Rods
Rods
- black + white
- dim lights
- edges of retina
- peripheral vision
Photoreceptors
special nerve cells at the back of eye, detect visual stimulus + transform light energy into nerve signals by rods + cones
Optic Nerve
- bundle of neurons that transmit visual information to the occipital lobe, runs though brain
Feature detectors
- specialised cells in the optic nerve that pick out specific lines in an image based on length, angle or direction
Biological influences on visual perception
Physiological makeup
- structures may be damaged, deteriorated or negatively impacted in the womb - leads to compromised visual perception
- eg. colour blindness - structural issue of the cones (long - red, medium - green, short - blue) / achromotopsia - lack of cone vision, only see inblack + white-
age related influences on visual perception
ageing
- presbyopia - lens loses elasticity, causes difficulties focusing on objects close
- floaters - clumps of matter that appear as small specs or 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 vision
- age-related muscular degeneration - a build up of grain deposits in the centre of the retina causing deterioration of central vision
Genetic influences on visual perception
Inherited visual disorders
- cross eyes, lazy eye, refractive errors and astigmatism
Congenital visual disorders
- visual disorders present at birth: glaucoma, cataracts, achromatopsia, optic nerve hypoplasia / some treatable
Retinis Pigmentosa
- degenerative disease affecting the retina - gradual loss of vision.
psychological influences on visual perception
selection = organisation of visual information occurs through:
perceptual/visual constancy - the tendency to maintain a stable perception of a stimulus although the properties of the image onthe retina may change
size constancy - the ability to know that the object’s size doesn’t change as it move closer/further away
shape constancy - the ability to know that an object’s shape doesn’t change even if our viewpoint changes
Gestalt Principles
- size constancy
- shape constancy
1) figure ground organisation: images are organised into the central object of attention (figure) and a background (ground) (the figure and ground are separated by an imaginary contour)
camouflage
2) closure - when an object is perceived as being whole despite actually being incomplete
3) similarity - elements that are similar in appearance will tend to be seen as a unit
4) proximity - the individual parts of a stimulus pattern are close together, allowing those parts to be perceived visually as a whole unit
Depth perception
the ability to accurately judje 3D space and distance using cues in the environment
binocular depth cues
- use both eyes to guage distance + space
- retinal disparity
binocular depth cue that arises as the brain
compares/contrasts the 2 slightly different images obtained
from each eye
- convergence
the automatic turning of the eyes inward as an object
approaches
- accomodation
the process by which the ciliary muscles of the eye change the
curvature of the lens to focus an image
Monocular Depth Cues
- depth cues that use one eye independently or both eyes together to gauge distance + space
Pictoral Depth Cues
- artistic, used to make 2D surfaces appear 3D
- linear perspective - parallel lines appear to converge as they
retreat into the distance
- interposition - objects further from the observer are partially
observed by the foreground
- texture gradient - texture in the foreground is seen in finer detail
than that further away
- relative size - our tendency to perceive the object producing the
largest retinal image as being the nearest vice versa
- height in the visal field - objects further away are closer the to
horizon
Perceptual set
predisposition to attend to certain aspects of the visual scene or to interpret stimuli in a particular way, according to certain preconceptions
- context: the situation in which we see something can shape our expectations
- motivation: we see what we want to see - our desires + needs can affect what we perceive
- emotion: our own feelings impact how we percieve others
Ponzo illusion
An illusion where two people perceive two lines of the same length as different lengths.
Muller-lyer illusion
1) carpentured world hypothesis
proposes our familiarity with the right angles + straight lines
informs our interpretations.
2) perceptual Compromise Theory
proposes we perceive the 2nd line as longer because of gestalt
principle of closure
