lecture six: cognition of visual perception

Question 1

why dont trees have a neural nervous system?

Answer 1

It doesnt move, therefore no need to know what is where.

Question 2

what is the inverse projection problem?

Answer 2

A given 3D object can create only one image on a 2D surface

A 2D image can be created by an infinite number of 3D objects

Question 3

does transsaccadic integration exist?

Answer 3

Result: change blindness. No transsaccadic integration

Question 4

unconscious inference

Answer 4

Inferences are automatic and unconscious Helmholtz (1860)

Our percept is the most likely solution of the perceptual “problem” posed by the world Helmholtz: likelihood principle

Question 5

What is Luminance constancy

?

Answer 5

The visual system takes shadow into account  chessboard with alternating black and white squares.

samecolor seems to be different, because of shadow perception

Question 6

Gestalt approach

Answer 6

The whole (Gestalt) is more than the sum of its parts
Max Wertheimer’s (early 20th century) critique on the structuralist view (e.g., Wundt)
Gestalt laws (principles / rules):
      - simplest solution
      - symmetry
      - similarity
      - proximity
      - good continuation
      - closure
      - common fate
      - familiarity (past experience)

Question 7

Top down:

Answer 7

expectancies, knowledge of the world

Question 8

Bottom-up:

Answer 8

Incoming data from the outside world

Question 9

Bayesian approach

Answer 9

Prior: your initial beliefs about the world (expectancies)
Likelihood: bottom-up evidence
 Posterior: update of your initial beliefs given the evidence

Question 10

echolocation

Answer 10

Echolocation experts make use of visual projection areas in the cortex (occipital lobe
Like vision, echolocation allows experts to determine what is where

Question 11

Familiarity

Answer 11

Once we have seen the “solution”, the stimulus acquires a fixed interpretation.

The interpretation is driven by what we know: familiarity

Question 12

Common fate

Answer 12

We group the elements with a common fate: same direction of movement.

We can also disambiguate by moving ourselves  some elements do not have common fate.

Question 13

Closure

Answer 13

We tend to complete incomplete figures when contours are partially missing

Question 14

Good continuation

Answer 14

How do you perceive the strings in Figure A?

Probably as in B rather than C: good continuation

Question 15

Simplicity

Answer 15

The perceptual system choses the simplest (least coincidental) solution (most likely)

Question 16

Predictive coding

Answer 16

Extension of the Bayesian approach:
The brain generates predictions all the time (top down)
Bottom-up information is compared to predicted information
No discrepancy? The brain does not respond.
Discrepancy?  Prediction error  Update beliefs

Question 17

Brain plasticity

Answer 17

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

Examples of Experience-dependent plasticity
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 make predictions and update beliefs