[Deck 3 - Motion Perception]

Question 1

Aperture problem

Answer 1

no one motion detector can detect direction of motion, lots of receptive fields need to converge in order to do so

Question 2

What are the 5 ways that we see motion?

Answer 2

~ Apparent motion
~ Induced motion
~ Autokinetic motion
~ Motion aftereffects
~ Real motion

Question 3

Apparent motion

Answer 3

e.g. Tv + flip books
~ when an object appears at one place, disappears and then reappears at another place
~ occurs between 30-600ms
~ phi phenomenon, shortest path constraint, correspondence problem all apply here

Question 4

Induced motion

Answer 4

~ moving environment can make you think you’re moving

~ background stationary + foreground moves

Question 5

Autokinetic motion

Answer 5

staring at an object for a long time = tired eyes –> the object appears to move

Question 6

Motion aftereffects

Answer 6

~ neurones are constantly firing = thresholds are needed –> motion cells activated + inhibited
~ when inhibiting cell tires, stops inhibiting = cell activation
~ when you stare at something for a long time the stare at a white screen, you see the reverse

Question 7

Real motion

Answer 7

especially tuned to recognise biological movement

Question 8

Phi phenomenon

Answer 8

diff. light presented in diff locations in a given time interval appears to be in motion

Question 9

Shortest path constraint

Answer 9

brain assumes direction of motion is always the shortest path

Question 10

Correspondence problem

Answer 10

you don’t know what ‘path’ the item/dot took

~ most times nearest neighbour principle is used

Question 11

How can the shortest path constraint be broken?

Answer 11

~ by bodily limitations –> people see biologically plausible movement

Question 12

Flicker fusion frequency

Answer 12

lowest frequency of flashing lights that’s percieved as constant

Question 13

Motion agnosia

Answer 13

a disorder where the world appears as if seen through a strobe light

Question 14

Explain ‘what the frog’s eye tells frog’s brain’

Answer 14

Lettvin et al. (1959)

~ will starve to death in room of dead flies - frog sees what it needs to in order to survive

Question 15

Ecological approach to perception

Answer 15

~ J.J. Gibson

~ perception is info based not sensation based

Question 16

The stimulus is…

Answer 16

… not impoverish is you move

Question 17

Optic flow

Answer 17

the motion of everything around you, as you move the objects/surfaces flow around you

Question 18

Where is there no optic flow?

Answer 18

At the focus of expansion

~ it doesn’t change as stays in the same place in the retina, everything around it changes

Question 19

Inverse projection problem

Answer 19

~ infinite objects can produce the same retinal image size

~ one object can produce infinite retinal image sizes

Question 20

What does a small visual angle mean?

Answer 20

person is far away