Task 5 mechanisms of middle and high level perception

Question 1

Structuralism

Answer 1

o Sensation: elementary processes that occur due to stimulation of the senses (seeing a flash of light)
o Perceptions: more complex conscious experiences such as our awareness of objects (accounts for the vast majority of our sensory experience)

Question 2

Apparent movement

Answer 2

o 1. One image flashes on and off 2. There is a period of darkness, lasting a fraction of a second 3. The second image flashes on and off
o Physically there are only two pictures but our perceptual system adds something during period of darkness

Question 3

Gestalt organizing principles

Answer 3

Parts of the gestalt theory, they determine how elements in a scene become grouped together. The starting point are things that naturally occur (more like heuristics than laws)

Question 4

Good continuation

Answer 4

points that when connected result in straight or smoothly curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path, Objects that are partially covered by other objects are seen as continuing behind the object

Question 5

Pragnanz

Answer 5

Every stimulus pattern is seen in such a way that the resulting structure is a simple as possible

Question 6

Similarity

Answer 6

Similar things appear to belong together, can occur because of similarity of shape, size or orientation

Question 7

Proximity

Answer 7

Things that are near each other appear to be grouped together

Question 8

Common fate

Answer 8

things that are moving in the same direction appear to belong together, even if the objects in group are dissimilar

Question 9

Common region

Answer 9

Elements that are within the same region of space appear to belong together

Question 10

Uniform connectedness

Answer 10

a connected region of the same visual properties, such as lightness, colour, texture, or motion is perceived as a single unit

Question 11

Closed contour

Answer 11

closed contours are more preferred than open ones

Question 12

Structural encoding

Answer 12

is based on the relationship between voxel activation and structural characteristics of a scene, such as lines, contrast, shapes. First it was calibrated by observing activity when certain stimulus was presented and then it has been reversed to make predictions other way around

Question 13

Sematic encoding

Answer 13

is based on the relationship between voxel activity and the meaning or category of a scene. Voxel activation is measured with number of stimuli that origin from one category. After the calibration the data was used to predict the other way around

Question 14

Subtraction

Answer 14

One measurement with stimulus and one with out to find activation in the brain caused by the stimulus

Question 15

Bayesian approach

Answer 15

Estimate of probability of an outcome determined by 2 factors
 Prior probability – initial estimate of the probability of an outcome
 Likelihood of the outcome –the extent to which the available evidence is consistent with the outcome

Question 16

Binocular rivalry

Answer 16

When both eyes see a totally different scene the brain perceives only one scene

Question 17

Recognition by components Model

Answer 17

The geons are based on the gestalt laws

Question 18

Structural description theory

Answer 18

objects are specified in terms of its parts and the relationship between the parts
 E.g. A = three lines – two flanking lines meet and a third spans the angle created by those two lines

Question 19

Geons

Answer 19

geometric icons as a collection of non-accidental features
 Viewpoint invariant – visual system should be able to recognise them equally accurately & quickly no matter what the orientation (as long as it’s not an accidental view)
 Minor shape variations won’t alter structural descriptions
 Combining geons can create a wide variety of object representations

Question 20

How do children learn to read and write?

Answer 20

• Have to unlearn invariant viewpoint to learn reading to distinguish between p and Q
• Literate people have a better pathway between visual and language areas

Question 21

What happens in the brain once we learn how to read?

Answer 21

• Letters are perceived by the visual word form area
• Visual wordform area: is massively affected
• Lateral occipital areas: increased their activation not just to words but also to all kinds of stimuli (faces, houses, checkerboards), learning to read has refined the capacity to recognize any picture
• V1: gets enhanced

Question 22

Inverse projection problem

Answer 22

The task of determining the object responsible for a particular image on the retina
 Because it starts with the retinal image and extending rays out from the eye

Question 23

View point invariance

Answer 23

The ability to recognize an object seen from different viewpoints

Question 24

Perceptual organization

Answer 24

the process by which elements in the environment become perceptually grouped to create our perception of objects
o Grouping: the process by which objects visual events are put together into units or objects
o Segregation: the process of separating one area or object from another (borders)

Question 25

Neuronal recycling hypothesis

Answer 25

o We are able to learn and read because of our preexisting circuits, there is one that links the left ventral visual pathway to the left-hemispheric language areas. This area is already capable of recognizing many letter-like shapes

Question 26

Naïve Template Theory

Answer 26

 Recognise object by matching every pixel/low-level feature of input to a representation in memory
 Array of spot detectors serves as a template
 Problem: too many templates required to not run out of brain as every “A” looks different
 Differentiates between objects with the same geon (improvement to Biederman)