Psychophysics, sensation, perception. How vision works, how the retina works. Theories of colour. Vision dysfunctions. Theories of vision. Theories of hearing. Taste. Smell. How touch works. Inattention, focused attention, divided attention. Theories of attention. Memory. Theories of memory. Types ...
Psychophysics
Sensation: sensory receptors & brain receives information form the environment
Perception: choosing information from sensation, organising it, interpreting it to make meaning
Threshold: the levels of energy required by a stimuli in order for it to be perceived
Absolute threshold: the minimum amount of energy needed
Difference threshold: the line one must cross to distinguish stimuli A from stimuli B
Just noticeable difference: the level at which people will notice a difference between two stimuli, 50% of the
time
.
The signal detection theory is when people don’t always detect a single at the same time or in the same
way
.
the first law of psychophysics is noticing a change depends on the proportion by which the stimulus has
changed
.
Subliminal perception is the register of sensory input without conscious awareness
.
Sensory adaptation is a decline in sensitivity to prolonged stimulation
Vision & The Eye
.
Light enters cornea — pupil — lens (turns image upside down) — retina
Visual acuity: how sharply a person can see objects & distinguished between them
Nearsightedness: distant objects are blurry
Cornea / lens bends too much or the eyeball is too long
:
Farsightedness: near objects are blurry
Eyeball is too short
The retina
The retina absorbs light, processes images & sends visual information to the brain
i If light falls on the optic disk = a blind spot
Its photoreceptors are rods & cones
Rods play a role in night vision
.
more sensitive to dim light & are all over the retina
.
Cones play a role in daylight & coloured vision
provides sharpness & detail
i Found in the fovea
,1. Light strikes rods & cones
2. this triggers the firing of neural signals into the retina
3. signals move from receptor to bipolar cells to ganglion cells
4. they send impulses along the optic nerve
5. this visual information goes through the optic disk
There are photoreceptors that activate when there is light (on-centre) & others that activate with the
:
absence of light (off-centre)
lateral inhibition/antagonism: when light falls on both centres and they compete with one another
Dark adaptation: threshold for vision lowers the more time you spend in the dark (less light needed for
vision)
cones adapt first & rods adapt slowly but improve night vision
Trichromatic theory of colour: photoreceptors pick up red, green & blue
opponent- process theory: neurons are able to process pairs of colours (red-green, yellow-blue, black-white)
Colours in pairs are on and off (yellow on, blue off)
i It takes both theories to explain vision
.
Trichromatic explains what happens in the retina
.
opponent explains processing in the optic pathways
How does visual information get to the brain?
.
Axons leaving each eye create the optic nerve — thalamus — primary visual cortex in the occipital lobe
.
signals from the right visual field are transmitted to the left hemisphere and visa vera
.
They cross over the optic chiasma
cortical blindness: damage of the primary visual areas
Primary visual areas = lower level tasks
i Secondary visual areas = allows us to see objects, colour & movement
.
Tertiary visual areas = allows us to write & to work with numbers
feature detection theory: neurons (feature detectors) in the visual cortex respond only to certain visual
stimuli
.
When feature detectors fire together information is integrated to create an image
, .
most visual input arrives in the primary visual cortex in occipital lobe
.
Information is further sent to temporal lobes (what?) and parietal lobe (where?)
Parsing: working out which elements go together
Every act of perception involves an act of judgement
.
Reversible figure: a drawing that has different interpretations that can shift
Principles of perceptual constancy: we use cues (colour, size, shape constancy) to keep our world predictable
& stable
Depth perception: seeing 3D space & judging distance
.
binocular depth cues depend on both eyes, convergence & retinal disparity
.
Monocular depth cues depend on one eye, linear perspective, patterns of light & shadow, relative motion,
motion parallax & texture
interposition: objects near appear to overlap ones that are further away
Movement parallax: head moves side to side, objects @ different distances move @ different relative velocity
bottom-up processing detects specific features of stimuli and then recognises the stimuli
i. Top-down processing uses context to recognise stimuli
the Gestalt principle is a top-down process
Gestalt principle
.
Proximity = objects closest together are grouped together
Similarity = look the same are grouped together
: Continuity = organise information to produce smooth contours
closure = close gaps in objects to make a whole
i Common region = items within a boundary area
Contiguity = occurrences share both time & space a casual relationship is assumed
Visual illusions: when we pick up signals from the environment & come to an incorrect perception
Agnosia: failure to recognise objects
Prosopagnosia: failure to recognise objects
Apperceptive visual agnosia: cannot recognise shape or copied drawings
Associative visual agnosia: cannot assign meaning to an object - difficulty in transferring visual information
into words
Alexia: reading problems
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