The summarised notes on the topic of visual perception. Includes information on binocular disparities, optical illusions and tunnel vision. Night time vision and accommodation are also touched upon.
Lecture 7 – Visual Perception
1. The senses - Visual, Auditory, Olfactory (smell), Gustatory (taste), Tactile (touch), Vestibular
(balance, ear canal can be susceptible to high frequency pain that can cause vertigo),
Proprioception (perception of one’s body position, so one can close their eyes and know
where their body parts are) and Interoception (Understand what is happening in the body,
so hunger or temperature awareness) – Kinesthesis is different to proprioception, as it
involves understanding how our bodies move (we automatically know how to walk and how
to hold something)
2. Visual system: The components of the eye are a system than collects images through the
entry of light onto the respective cells to help create an image that the brain must flip and
later interpret
3. Colour vision: Involves physics; we see rainbows because of the white light from the sun’s
rays refracting through the concave droplets of clear rain, forming the continuous colour
spectrum as a result of the light bending and exposing the colour. Our vision can be
defective, resulting in only a few colours on the spectrum being visible; maybe our cornea
does not refract the light properly?
4. Visual adaptation: Our eyes are very sensitive to change, lie going from pitch black to bright,
so we have to give them time to focus once a new stimuli is bought in. Explains why it is hard
to get up in the morning (our eyes are extra sensitive to the change in darkness to suddenly
having light) and why when we walk into a dark room, everything looks pitch black (it takes a
while to see the areas where there is light) – Our eyes have centre vision and peripheral
vision, when we zone out we see things due to the strength of the peripheral fading as a
result of lacking focus, thus we see dark silhouettes or we see distorted images. Sometimes
we see optical illusions and assume they are in motion, when in reality the light and colours
we look at oppose each other and create moving images in our heads
5. Perceptual processing and Perceptual organisation: We perceive something, that would
otherwise throw us off, as something basic, so sometimes the letter A and the letter H may
be written the same, but due to our knowledge, we know the letter is not the same, as one
image can show two different things so the duck and rabbit image; gestalt psychology allows
us to focus on the whole image an interpret these multiple images rather than look at the
beak of the duck or the ears of the rabbit
6. Perceptual Constancy: Sizes and shapes are constant no matter what the angle is
7. Depth perception: The length, distance and elevation does not affect the dimensions of
something; having a stronger foreground does not mean the background is changing at the
same rate
8. Motion perception: Sometimes things just change, they do not move, but other times,
movement happens due to transferring of information between photoreceptors, creating
moving images
, 1- Senses
Sensation and perception – food can taste different if it looks bad, if it smells bad or if it has a
bad texture; perception is the interpretation of a stimuli, whereas the sensation is the stimuli
being detected and processed in our brains. Feeling a sensation then dictates what our
perception will be based on our individual preference and responses
2- Visual system
Iris: Provides eye colour depending on the pigment amount; membrane behind the cornea that
adjusts the pupil size in order to ensure too much or too little light is not coming in; it dilates the
pupil to help more light come in, and constricts when there is too much light, so it blocks it out
Pupil: Black hole in the eye, located in the centre iris; allows light to come through this hole and be
reflected onto the retina cells after complex refracting through other parts of the eye
Ciliary muscles: Changes the shape of the lens depending on the distance of the image we look at;
the muscles tighten with the suspensory ligaments loosening when the focus is on a closer object,
the lens is wide as no tension exerted by ligaments. The ciliary muscles relax, with the suspensory
ligaments contracting for distant objects, the lens is flattened due to tension from ligaments
Lens: Helps refract the light onto the retina
Optic nerve: Information received at the retina is sent to the brain from these millions of fibres
behind the eye
Sclera: Maintains the round shape of the cornea and prevents external and internal forces from
allowing the eyes muscles to rip apart
Cornea: Helps refract light onto the retina
Retina – Photoelectric cells that are the reason why we can see. Harsh exposure to light damages
these cells, blue frequencies in particular; it covers 65% of the back of the eye and it converts the
signals from the light received by the lens and sends the input to the brain
Blind Spot: Point at which the optic nerve and blood vessels leave the eyeball and go to the brain
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