Lecture 2 Flashcards
What does it mean ‘cognition is grounded in perception’?
dreams relate to what we’ve seen
“ I see what you mean”
we understand seasons because we SEE the changes
Perception is subjective
we don’t all see the same thing, we all view the same things differently
subject to interpretation
Vision starts with the detection of light
light is the stimulus
eyes are the receptors
Visual receiving area
deconstructs images
specific areas in the visual cortex
different areas in the visual cortex focus on different things. some focus on colour, some horizontal lines and others vertical lines
are visual cortex views things fragmented
light is made up of photons
these photons are on different wavelengths depending on their vibrations
what wavelength can humans detect
between 400 and 700nm
why can’t we see when its dark?
when its dark, there is light energy but as we only see small amounts of visible light, we don’t detect this enerygy
different animals = different wavelengths
for example, dogs can’t see red they associate it with green as they have a much smaller wavelength than humans
Reflections
light reflects of objects and determines what we see and the colours we view
certain surfaces reflect wavelengths and others absorb it
Distal stimulus
the physical objects that reflect light
Proximal stimulus
the image of an object on our eyes
why do the retinal images appear upside down?
due to the concave surface inside the eye
iris
the coloured structure surrounding the pupil
pupil
constricts and relaxes to allow light into the eye
cornea
transparent structure on the outer eyes surface
yellows with age and scratches
lens
focuses light into the eye and onto the back of the eye
retina
contains the light sensitive cells - photo receptors
fovea
contains majority of the photoreceptors and allows for detail and coloured vision
cones
photopic visual system
found near or in the fovea
work best in intense light
detect high wavelengths - bright blue, red and green
detects high frequencies - fine detail
rods
scotopic visual system
found in the retinal periphery
work best in low light
detect low wavelengths - greys
detect low frequencies - coarse detail
dark adaptation
the gradual improvement in the ability to see in the dark
takes up to 20 minutes
in low light levels, only rod mediated vision is sensitive enough to detect light
light adaptation
the gradual improvement to see in dim light
takes 5 minutes
at high light levels, only cone mediated vision is possible, rods become bleached
Ganglion cells
receive input and carry information from the eye to the brain
Focusing
focusing light on a certain object is known as forviate
allows lots of detail, the rest around you is still colourful when in reality this is an interpretation and not how your brain sees the world as the rods are working and they can’t detect colour or detail (blurry and grey)
Why is it hard to read at night?
due to the distribution between cones and rods across the retina
Blind spot
a hole in the retina where there are no photoreceptors
why aren’t we aware of these blind spots?
as our brain fills in the gaps with “what is mostly likey there”
Why do we need to see colour?
important for survival
adds beauty to our lives
a psychological phenomenon
hue
the colour quality of the light
saturation
purity of the light
brightness
amount of light present
white surfaces
reflects all wavelengths
tri-chromatic system
3 types of cones
short wavelength - blue
medium wavelength - green
long wavelength - red
red-green colour deficiency
lost or limited function of the red cone pigments
caused by recessive gene on X chromosome, more common in men
instrumental in realising the existence of 3 types of cones in the human retina
opponent process theory
trichromatic theory can’t explain:
the primary colours for most are red, green, blue and yellow
those colour blind to red are also colour blind to green
negative after images
opponent process theory
some ganglion cells process information differently about the firing rates of long and medium cones, this gives us the perception of red or green
others process differences between short concessions and long and medium cones, giving s the perception of yellow and blue
negative after images
experiences of one collet after the removal of another
Is colour vision critical for survival?
people can live with colour deficiencies
we don’t need colour to see motion
colour vision therefore probably it not critical but is a useful ability to have that allows us a fuller experience of the world
