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Chapter 2. Perception
•There are two issues with this:
oThere are too much sensory inputs from the environment
oThere are too little focused information from environment
2. How it works the case of visual perception
•The goal of perception is to get information front he world and make
sense of it
•Vision= distance sense, it is used to make a perception without direct
•It takes information about the properties and the location of objects
so that we can make sense of where it is and interact with it.
2.1 The structure of the visual system
oLayers of cell that respond to light
•Light is converted into an electrochemical signal which is passes
through the optic nerve
• Each optic nerve id the axon of a long ganglia cell in the retina
• The axons make a contact with the lateral geniculate nucleus int he
• From there the thalamus sends a impulse to the PRIMARY visual
2.2 top-down and bottom-up processing
When you get and send signals both ways
•Lga to visual cortex and back and forth
oBottoms up process
Driven by sensory information from the physical world
Driven by out knowledge beliefs and expectations and
•Mosr processes involve these two put together.
•But some distinctions better bottoms up and top down are that top
down is slow
2.3 learning to see
Our interpretations depend on two things:
1.Our brain structure
2.Experiences that changes the brain structure
For example if there was 1 cat with a patch over its one eye from infancy
then it will grow to have bad perception when the patch is taken off but if
both eyes are covered by the patch then the cat can adjust later on using
3.bulding from the bottom up: from features to objects
3.1 Processing features, the building blocks of perception
•Visual features are also spots and edges , colours and shapes
•When you combine these things you get objects
3.1.1 spots and edges
•One of those neurons in the retina whose axons fibers from the optic
•The area of the visual field in which a stimulus will affect the
activity of the cell.
There are two things that can happen when there is a stimulus , it can
either excite the ganglion cell or inhibit it.
It can reach from 10-100 units
•A set of solid colour in a gradient, and we see edges on it because of
the photoreceptors and ganglion cells in our eyes.
3.1.2 throwing away information
Showed if you cover this imagine the middle you will see only 1 shade, this
means that visual perception efficiently ectracts visual feates by ignoring
3.1.3 nueral processing features.