lecture 5 *biology and cognition*

Perception = experience resulting from stimulation of the receptors

Perception is dependent on consciousness : a tree doesn't have perception while humans and animals do

perception serves the organism to establish what is going on where in the outside world ( also inner world )

perception has evolved in order to support the species in their natural habitat

technique used by bats, dolphins and other animals to determine the location of objects using reflected sound

occipital lobe

echolocation experts make use of visual projection areas in the cortex

dorsal : HOW / WHERE BRAIN

ventral : WHAT BRAIN

bilateral lesions in the occipital temporal lobe

ventral route affected (what pathway)

dorsal route unaffected

left : models that DF was asked to copy

middle : DF's attempts of copying the models not any close to the original

right : DF's drawings from memory : much closer resemble

light / eye/ lens/ retina eceptors

in human visual perception we establish what is where by information reflected by light

1. photoreceptors sensitive only to light
2. world is 3D retian is 2 D
3. only 1/2 degrees of visual angle falls on the fovea

light : a small part of electromagnetic spectrum

there are more spectrums, the eyes do not see all ( radio , infrared, x rays , gamma rays )

a 2D image can be created by an infinite number of 3D objects retia is only 2D

1/2 degree of visual angle falls on the fivea

blind spot

on the outsides : high density rods

in the middle high density cones

**he total area in which objects can be seen**

1. The image of the world upside down and left right reversed (not really a problem )

The leftight visual field are represented crossed and upside down

Recreate a full image of the world to portray to our inner self

the mind in not a "Cartesian theatre "

there is no homunculus inside

perception is very selective : a lot of information is not registered

use the data on our photoreceptors (in the retina ) to make inferences about what is where

automatic and we're mostly unaware of making them

our percept is most likely solution of the perceptual "problem" posed by the world Hermholtz

three black pacmen or white triangle on black disks?

If triangle you also see its sides (illusory edges)

Checkerboard with dark and white squares

but how much different are black square A and white square B psychically ?( i.e on our retinas)

1. most likey solution
2. unconscious inferences

the most plausable option

speech perception : you can hear words separatly without the person making braks

one stimulus, infinite number of interpretations (even without the 2D/3D inverse projection problem : we asume the easist
what do strategies do we use ?

heuristics : Gestalt approach

1. simplest solution
2. symmetry
3. similarity
4. proximity
5. good continuation
6. closure
7. common fate
8. familiarity (past experience )

choose the siplest solution ( two triangles one behing the other )

symetrical outlines are grouped together

the similar colours/patterns are grouped together ( woman at the beach )

objects close together are grouped

lines that go in same direction seem to continue eachother

complete incomplete figures when contours are partially missing, grouping them into

group the elements with a "common fate" (same direction of movement) into an object.

Once we have seen the

"solution", the stimulus acquires

assume light comes from a direction because that is the knowledge we have

incoming data form the outside world

own expirinces and knowledge of the world

human brain has been evolved over millions of years of evolution, but it is shaped during its life time

Daniel Kish learned to use his occipital lobe for echolocation

Kittens raised in an artificial world with only vertical black and white stripes ignore horizontal objects later on (Blakemore & Cooper, 1970)

Normal knowledge acquisition enables us to interpret an ambiguous world, make predictions, and update beliefs