Sensation and perception 1 Wk 5 Flashcards
what is sensation?
the process by which the sense organs (eg. eyes, ears, skin ) gather info about the environment
what is perception ?
the process by which sensory info is selected and processed, selected, organised and interpreted
what is transaction ? describe it
energy - neural impulses
coded in terms of :
- intensity
- quality
sense receptors ‘transduce’ stimuli into signals
what are psychophysics?
study of how we perceive sensory stimuli, bases on their physical characteristics.
what is an absolute threshold?
it is the lowest stimulus (on its own) that we can detect 50% of the time
–Smallest change in intensity of a stimulus that we can detect
–Depends on:
a)Level of intensity of new stimulus
b)Level of stimulation already present
what is attention
a mental phenomenon of concentration and it shifts focus
- influenced by external and internal events
- limited capacity
what is selective behaviour?
allows us to select some inputs for further processing and ignore others
.–Reticular activating system (RAS) and basal forebrain activate regions of cortex (e.g., frontal cortex)
what is the bottle neck theory of attention?
broadband (1958)
- early filtering mechanism
- limited capacity channel
what does the cocktail party phenomenon suggest about selective attention?
some info actually gets through the filter.
Even when we selectively attend to conversation we are subconsciously monitoring other conversations around us
what are the errors of attention?
- in-attentional blindness (a failure to see something in plain sight)
- change blindness (the inability to detect changes in scenes when looking directly at them)
what is divided attention?
it is performing multiple tasks simultaneously
what is considered one wave length and wave amplitude
wave between two peaks. Amplitude height and determines intensity
we can only see a very small part of the light spectrum
3 parts of the eye (basic)
1) sclera (white part)
2) pupil (light comes in)
3) iris
what are the two processes of the inside of the eye
1) focussing light on retina
2) Transducing the image into nerve signals
what are photoreceptors?
photoreceptors (lights and cones) turns light energy into electric signals
-electrochemical processes mediated by photo pigments
describe the rods in photoreceptors
- low light
- monochromatic
- peripheral vison
describe the cones in photoreceptors
- bright light
- colour vision
- central vison
different part of the visual cortex
Different cortical cells respond best to different stimuli–
Simple cells: light of specific orientation at a particular location
Complex cells: specific orientation but less dependent on location
Feature detectors: lines and edges (simple/complex cells), length of lines, shapes, movement, colouretc.
what is colour vision?
different theories explain different aspects of colour vision
both theories have proven to be correct.
1- Trichromatic
2- Opponent process
what is one theory of colour vision?
trichromatic theory: colour vision is based on our sensitivity to three primary colours
- explains colour blindness
- consistent with three types of cones in eyes
what is the opponent process theory of colour vision?
- colour vision as a function of complementary opposing colours
- red Vs green
- blue Vs yellow
- black Vs white
what are some causes of blindness
cataract 47.8% people worldwide treatable.
glaucoma 12.3% treatable
Macular degeneration 8.7% not treatable
diabetic retinopathy 4.8% not treatable
childhood blindness 3.9% some types are treatable
what is the basic outline of colour blindness
there are three types
- monochromic
- dichromacy
- (anomalous) Trichroma
most usual cause is faulty cone development
-genetics: far more common in males
what is one test of colour blindness
Ishihara test. Letters in coloured pictures
what is motion blindness?
inability to perceive motion (or ‘stitch together’ the incoming images)
what is visual agnosia
inability to recognise objects, despite normal ability to describe the shape and colour etc
brightness and hue
we perceive brightness (intensity) and hue (colour)
- mixing lights produces white (additive)
- mixing pigments produces black (subjective)
what do the lens inside the eye do?
transparent disk that focuses light rays for near or distant vision
what does the cornea inside the eye do?
curves, transparent dome that bends incoming light
what does the iris do?
coloured area containing muscles that control the pupil
what is the pupil?
opening in the centre of the iris that lets In light
what is the eye muscle
innermost layer of the eye, where incoming light is converted into nerve impulses
what is the optic nerve in the eye
transmits impulses from the retina to the rest of the brain
what is the fovea at the back of the eye (point of central focus)
the part of the retina where light rays are most sharply focused
what is webers law
regardless of the magnitude of the two stimulus, the second must differ from the first by a constant proportion for it to be perceived as differnt
what is the average weber fraction for weight
1/50
what is signal detect theory
sensation occurs when we judge whether a stimulus is present or not
what 2 processes contribute to signal detection theory
1-initial sensory processes
2- decision process
what is the visible spectrum of light
400-700 nanometers
characteristic of vision
image is inverted on retina , which turns in into an AP
cornea?
direction and focusing, clear part of eye
sclera?
white part of eye, refocuses light
choroid?
muscle area attached to lens
retina?
holds lights sensitive cells, innermost layer of the eye where light is converted to nerve impulses
macula?
contains fovea
fovea?
part of the retina where light is focused more sharply
most concentration of cones
pupil?
opening that lets the light in
what is cortical blindness?
cannot identify shapes
