Week 5

Question 1

Pareidolia

Answer 1

is the phenomenon of perceiving a vague stimulus as something of importance.

The visual system may be biased to create (recognize) a perception that is ambiguous in the stimulus

Question 2

parahippocampal cortex

Answer 2

PPA
Responds best to spatial layout (including
buildings and places, top row)

Question 3

Extrastriate body area (EBA), in
occipitotemporal cortex

Answer 3

Responds best to pictures of full bodies and body parts (top row, not faces)

Question 4

Binocular rivalry

Answer 4

each picture shown to one eye at the same time.
Picture of a house shown to one eye and a face to another. You can only perceive (i.e. be aware of) one at a time.

Question 5

Experiment by Tong et al.

Answer 5

Used Binocular rivalry

Participants pushed button to indicate
what they perceived.

fMRI showed an increase in activity in
* Parahippocampal place area for the house
* Fusiform face area for the face

– Demonstrates how perception and
recognition correlate with specific brain
activity.

Question 6

Inverse projection problem

Answer 6

An image on the retina can be caused by an infinite number of objects. [Many different distal stimuli can create similar proximal stimulus.]

Question 7

Object perception is hard

Answer 7

1. The stimulus on the receptors is ambiguous.
   - the inverse projection problem
2. Objects can be hidden or blurred.
3. Objects look different from alternative viewpoints
   - viewpoint invariance

Question 8

Viewpoint invariance

Answer 8

the ability to recognize an object regardless of the viewpoint/perspective.

hard for computers to perform

Question 9

structuralism

Answer 9

Established in late 1800s by Wilhelm Wundt

– Stated that perceptions are created by combining elements called “sensations.”
– Hierarchical, well-ordered approach to perception. Strongly “bottom-up.”
– However, structuralism could not explain apparent movement

Question 10

Apparent Movement

Answer 10

Motion is perceived when separated objects (e.g. dots, bars, etc.) flash in different locations, but without the necessary sensory atoms predicted by structuralism

Question 11

Gestalts approach to object perception

Answer 11

• The whole differs from the sum of its parts.
  – Perception is not built up from sensations, but is a result of perceptual organization. [strong top-down influence]
  – The mind (somehow) makes simple assumptions about objects in order to recognize them in the environment.
• Principles of perceptual organization
  – 8 principles for organizing objects within perceptual scenes have been offered: pragnatz (good figure/simplicity), similarity, good continuation, proximity (nearness), common region, uniform connectedness, common fate, and meaningfulness.

Question 12

1. Pragnanz

Answer 12

(good figure/simplicity)
* Every stimulus is seen as simply as possible
* The easiest interpretation takes fewer cognitive resources.

Question 13

1. Similarity

Answer 13

• Similar things are grouped together
• Color is one measure of similarity (e.g. grouped into columns), but it could be shape, orientation, etc.

Question 14

3. Good continuation

Answer 14

Connected points resulting in straight or smooth curves belong together.
– Lines are seen as following the smoothest path
– Holds true even complex images

Question 15

4. Common region

Answer 15

elements in the same defined region tend to be grouped together.

Question 16

5. Proximity

Answer 16

Things that are near to each other are grouped together.

Question 17

6. Uniform connectedness

Answer 17

connected regions of visual stimuli are perceived as a single unit.

Question 18

7. Meaningfulness or familiarity

Answer 18

Stimuli form groups if they appear familiar or meaningful8

Question 19

8. Common fate

Answer 19

Things moving in same direction are grouped together

Question 20

figure-ground segregation

Answer 20

determining what part of the environment is the figure and which is the background.

Question 21

Properties of figure

Answer 21

More “thinglike” (i.e. can be acted upon) and more memorable than ground.
– The figure is seen in front of the
ground.

Question 22

Properties of ground

Answer 22

– The ground is more uniform (e.g. one color or texture) and extends behind the figure.
– The contour separating figure from ground belongs to the figure (border ownership).

Question 23

Factors that determine which are is the figure:

Answer 23

Elements located in the lower part of displays tend to be interpreted as figures (objects of interest)

– Units that are symmetrical
– Elements that are small
– Units that are oriented vertically
– Elements that have meaning

Question 24

RBC theory

Answer 24

Definition: We recognize objects by volumetric features called geons.
(36 geons (cylinder, rectangular solids, pyramids, etc.) that combine to make
all 3D objects.)

Question 25

Geons have the following properties to solve problems of object perception:

Answer 25

● View-invariant properties
● Non-accidental properties
● Discriminability

Question 26

View-invariant properties

Answer 26

The ability to recognize an object regardless of the viewpoint/perspective.
○ Edges that are usually visible.
○ Because of these edges, we can tell that it’s a rectangle.

Question 27

Non-accidental properties

Answer 27

Edges in the retinal image correspond with the 3-D environment.
○ We can always recognize TYPICAL objects, but not accidental objects.

Question 28

Discriminability

Answer 28

The ability to distinguish geons from one another.
○ Because we have the view-invariant and non-accidental properties, we can distinguish each of the geons very easily.

Question 29

Principle of componential recovery

Answer 29

Definition: The ability to recognize an object if we can identify its geons.

Question 30

scene

Answer 30

A scene is a real-world environment that contains:
- background elements.
- objects organized in meaningful ways with each other and the background.

Question 31

gist

Answer 31

A gist of a scene is a quick understanding and recognition of major elements in a complex picture or sequence.

● Potter, Mary (1976) showed that people can do this very accurately when a picture is only presented for 250 ms (90% in trial below).
● Li Fei Fei (2007) extended this research to demonstrate the range of information that becomes available with more viewing time, extending from 27–500ms.

Question 32

Physical regularities

Answer 32

regularly occurring physical properties

Question 33

Oblique effect:

Answer 33

people perceive horizontals and vertical more easily than other orientations.

Question 34

Uniform connectedness

Answer 34

objects are defined by areas of the same color or texture.

Question 35

Light-from-above assumption

Answer 35

light in natural environment comes from above us.

Question 36

Theory of unconscious inference

Answer 36

Perceptions are result of unconscious assumptions about the environment. (top-down)

Question 37

Likelihood principle

Answer 37

objects are perceived based on what is most likely to have caused the pattern. (so we can make the unconscious inference.)

Question 38

Bayesian Inference

Answer 38

○ A modern interpretation of the Likelihood Principle.
○ Takes prior experience/ probabilities into account.

Question 39

Predictive coding

Answer 39

suggests that prior information establishes expectations that are compared with current inputs.

if signal normal you proceed, if its unexpected you get a prediction error PE. this pe may cause you to reconsider your expectations or reevaluate the stimuli.

Question 40

Contextual modulation

Answer 40

Stimuli (images) outside of a neuron’s receptive field can affect neural firing. happens when:

● when these stimuli follow good continuation.
● when the stimuli are perceived as part of the figure.
● when the stimuli are consistent with the role of top-down influence on perception and
recognition.

Good continuation: connected points
result in a straight line

Question 41

Real motion

Answer 41

an object is physically moving across space.

Question 42

Illusory motion

Answer 42

no real motion present, but it is perceived.

Question 43

Apparent motion

Answer 43

Stationary stimuli are alternately presented in different locations.
(Basis of movement in movies and TV)

Question 44

Induced motion

Answer 44

Real movement of one object results in the perception of movement in another object.
○ moving clouds may make the moon appear to move.

Question 45

Motion After Effect

Answer 45

a. Observer looks at (perceives) movement of object for 30 to 60 seconds.
b. Then observer looks at a stationary object.
c. Movement occurs in the opposite direction from the original perceived movement.
(The waterfall illusion is an example of this)

Question 46

What accounts for the motion after effect?

Answer 46

MT Medial Temporal Lobe

Question 47

Spiral Motion After Effect

Answer 47

– MT cells converge on cells in the medial superior temporal – dorsal (MSTd) area.
– These cells respond to ‘optic flow’ – the relative motion of you going through your environment.
– Watching an expanding optic flow pattern can selectively adapt MSTd neurons.

Question 48

Reichardt detectors

Answer 48

are circuits that fire to real movement in a specific direction, while the eye is stationary.

Question 49

Aperture problem

Answer 49

observing a small portion of a larger stimulus may lead to misleading (ambiguous) information about the direction of movement

• Activity of a single complex cell does not provide sufficient information about
  direction of movement.

Question 50

Solution to Aperature Problem

Answer 50

A number of cells in V1 have hierarchical convergence into higher areas. One of which is middle temporal (MT) cortex , which is part of dorsal (where/how) stream. This area is responsible for directional motion, and more specifically, coordinated motion.