Perception

Question 1

Defining Perception?

Answer 1

Possible definitions:
– the act of becoming aware of something through our senses
– Pattern recognition: ability to detect meaningful patterns in the environment (faces, objects, etc.)

Question 2

Why study perception?

Answer 2

Perception is not always equivalent to reality

Sometimes perceptual errors offer a clue to how visual cognitive processes work (such as optical illusions)

Understanding perception helps designers create user-friendly displays

Question 3

Inverse Projection Problem?

Answer 3

Determining the object responsible for a particular image on the retina

Objects can be hidden or blurred

How do we got rom this 2 dimensional picture to the experience of 3 dimensions?

Question 4

View Invariance?

Answer 4

If the primary visual cortex only gets a 2D map from one
angle, how do we know what an object looks like from other
angles?

How do we know what the bottom of a chair looks like from seeing it from another angle?

Question 5

Size Constancy?

Answer 5

How do we know something is the same size at different
distances, since when it’s further away it is smaller on our retina?

Question 6

Perceptual processes?

Answer 6

Bottom-up processing:
Basic elements come together until the mind reaches a higher level of understanding

Top-down processing
Prior knowledge or context are used to analyze incoming information to inform perception

Question 7

Helmholtz’s Theory Of Unconscious Inference? and what principle?

Answer 7

Some of our perceptions are the result of unconscious assumptions we make about the environment

Likelihood principle-we perceive the world in the way that is “most likely”based on our past experiences (Top down inference using prior knowledge)

Question 8

Gestalt Principles of Perceptual Organization - Similarity?

Answer 8

Elements that look similar will be perceived as part of the same form or group

Question 9

Gestalt Principles of Perceptual Organization - Proximity?

Answer 9

Elements that are close together will be perceived as a coherent group

Question 10

Gestalt Principles of Perceptual Organization - Closure?

Answer 10

Humans tend to enclose spaces by completing a contour and ignoring gaps in a picture

Question 11

Gestalt Principles of Perceptual Organization - Common Fate?

Answer 11

If two or more objects are moving in the same direction and at the same speed, they will tend to be perceived as a group

Question 12

Gestalt Principles of Perceptual Organization - Symmetry?

Answer 12

Images that are perceived as symmetrical are experienced as belonging together

Question 13

Gestalt Principles of Perceptual Organization - Good Continuation?

Answer 13

People tend to connect elements in a way that makes the elements seem continuous or flowing in a particular direction

Question 14

Bayesian Inference?

Answer 14

Our estimate of the probability of an outcome depends on…

Top-down perception using:
1. Prior probability (“prior”) of the outcome
2. How much the available evidence is consistent with the outcome (“likelihood”)

Question 15

From eye to cortex? (4)

Answer 15

Eye -> Optic nerve -> Lateral Geniculate Nucleus -> Visual Cortex

Question 16

What and Where Pathways?

Answer 16

Ventral Stream: What (Object recognition)
Primary auditory cortex

Dorsal Stream: Where/How (Movement and spatial relations)
Primary visual cortex

Question 17

Inferotemporal Cortex (IT)?

Answer 17

• Front end of ventral stream
• Cells selective for object categories
• Some regions selective for faces
• “View invariant”

Question 18

Object identification: 2D image to 3D objects? (Ventral Stream)

Answer 18

Common to many theories:
- Reconstruct representations (or structural descriptions) of objects
- Match them to some kind of temple

Question 19

Bottom-up Processing for object identification?

Answer 19

Extract basic features from a stimulus and compare to known patterns of stimulus features stored in long-term memory

There are at many different descriptions of how we employ basic bottom-up processes
- Distinctive Features Theory
- Recognition by Components Theory
- Template-Matching Theory
- Prototype Theory

Question 20

Distinctive Features Theory?

Answer 20

All complex perceptual stimuli are composed of distinctive and separable attribute called features
- Allow observers to distinguish one object/person form another
Pattern recognition is accomplished by mentally assessing the presence or absence of a checklist of curial features

Question 21

Recognition by Components Theory?

Answer 21

Describes the pattern recognition process in terms of how people recognize 3-D objects—by identifying the building blocks that make up the objects

Basic elements are composed of an alphabet of 36 primitive shapes, called geons
- Geometic icons
- Building blocks for identifying #D objects

(solves the view invariance problem)

Question 22

Template Matching Theory?

Answer 22

• We store an unlimited number of patterns, literal copies corresponding to every object that we have experiences
• These patterns are labeled with the name of the object
• New instance matched to stored templates
• Informs us of the name

Question 23

Problems with template matching theory?

Answer 23

• It is highly impractical when the set of possible patterns is very large
• Inefficient and fails to account for our ability to recognize new objects
• Example, How do we manage to read the handwriting of a person we just met?

Question 24

Prototype Theory?

Answer 24

Template is not a literal match with an object, but is an average or typical instance of the many different views of that object

This average is called a prototype andthe theory that uses them for pattern recognition is called prototype theory

Pattern recognition occurs when the features of the object to be recognized overlap with the features of the prototype

Question 25

Prototype Theory does not require?

Answer 25

An exact match between the object and the prototype The storage of patterns for every possible view of an object

Question 26

Prototype Theory test: For each prototype, researchers created individuals that varied in their degree of similarity to the prototype Stage 1: learning phase Stage 2: judgment phase (old/new face) Result?

Answer 26

The prior faces that they saw they had higher confidence that they'd seen before. The faces they had not seen before had a low confidence of seeing them before. But there was 100% confidence that they've seen the prototype face, even though they never seen it. Moreover, the more similar the faces were to the prototype the higher was the confidence that they've seen them before.

Question 27

Facial Prototypes?

Answer 27

Faces are highly varied and, except in rare circumstances, no two are alike Yet they share significant similarities - Always contain the same set of parts - Always appear in the same basic configuration

Question 28

The Thatcher Illusion?

Answer 28

Typical face processing: gestalt-like manner, using spatial relations among the face parts to construct a holistic view When the face is rotated, we switch to noticing the individual facial features—the component information (more common for non-faces)

Question 29

Facial Prototypes -> We’re better at recognizing faces when they are right side up and looking forward then when upside down?

Answer 29

We have only developed a prototype for right-side-up faces The fact that we are poor at recognizing upside-down faces suggests that we don’t have practice seeing faces in that position

Question 30

Neural circuitry for face recognition? (FFA) which is inside the?

Answer 30

One of several areas of the brain that play a key role in face recognition is a region of the fusiform gyrus called the fusiform face area (FFA) FFA is inside fusiform gyrusis inside inferotemporalcortex (Ventral stream)

Question 31

FFA is part of face-selective network

Answer 31

Functional imaging in monkeys has revealed nine faceselective patches in temporal and prefrontal cortex

Question 32

Prosopagnosia?

Answer 32

Inability to recognize familiar faces (face blindness) Not a result of visual, intellectual, or memory difficulties May be able to recognize people by their voices, names, or by superficial features (e.g., hair color) Rely on more featuralprocessing

Question 33

Top-down processing?

Answer 33

Using knowledge stored in long-term memory to further analyze incoming information in order to complete the identification - Expectations - Context - Interpretations - Biases

Question 34

What is a feedforward process?

Answer 34

V1 -> V2 -> V3 ->IT When signal or information get passed forward from one area to the next Bottom up processing involves mostly feed-forward processes as infraction gets passed on from V1 forward V1 <- V2 <- IT <- PFC When signal or information gets passed backward from a higher level (further from V1) area to the a lower level one Feedback processes are important for top-down influences on face and object recognition

Question 35

Key Brain Regions? V1 or primary visual cortex, IT or inferotemporal cortex, & Fusiform Face Area (FFA)

Answer 35

V1 or primary visual cortex, which is where information from the eyes reach the cortex and the beginning of both dorsal and ventral visual streams Prefrontal cortex or PFCis important for taking context into account in top-down influences on face and object processing IT or inferotemporal cortex which is important for recognition of whole objects Fusiform Face Area (FFA): A region of the fusiform gyrus in IT that is an important part of the face network

Question 36

Top-down contributions study. Used fMRI and MEG to determine when and where in the brain object recognition occurred Information got to the frontal lobes for recognized objects before it reached inferotemporal cortex (IT) Conclusion?

Answer 36

The frontal lobes predictan object’s identity and help fine tune the representation in IT

Question 37

Speech perception? (3+ principle)

Answer 37

Top-down processing influences our perception of language based on our individual experiences with manage Some perceptions are the results of unconscious assumptions we make about the environment -> We use our knowledge to inform our perceptions We infer much of what we know about the world Likelihood principle: We perceive the world in the way that is "most likely" based on our past experiences

Question 38

Speech segmentation?

Answer 38

The ability to tell when one word ends and another begins

Question 39

Transitional probabilities?

Answer 39

Knowing which sound will likely follow another in a word

Question 40

Statistical Learning (Saffran)

Answer 40

Infants 8 months or younger can learn transitional probabilities Invented nonsense words using a regular pattern and unregular patterns to form the word -> low and high transitional probabilities 8 month old infants showed more interest in novel words, with low transitional probabilities

Question 41

Regularities in the Environment? & Oblique effect?

Answer 41

Common physical properties of the environment Oblique effect: (means an angled line) We perceive verticals and horizontals more easily than other orientations

Question 42

Light-from-above-assumption?

Answer 42

We assume light comes from above because this is common in our environment We perceive shadows as specific information about depth and distance

Question 43

Semantic regularities and Scene schema?

Answer 43

- Semantic context that helps us perceive contents faster - Top-town context provides perceptual processes with expectation what is coming

Question 44

Optic Ataxia?

Answer 44

A clinical disorder that causes problem with "visually-guided" behaviour stemming from impaired representations in the dorsal (where/how) pathway. Demonstrating that it is a distant process from identifying what the object is (ventral pathway).

Question 45

Apperceptive Agnosia?

Answer 45

Failure of perception in which some basic visual functions (acuity, color, motion) are preserved, while others, (shape, angle, size) may be disrupted Damage to the ventral (what) pathway

Question 46

Associative Agnosia?

Answer 46

Apperceptive agnostic people can have difficulty recognising objects, but it is due to deficits perceiving simple visual information (angle/width). They still have preserved object knowledge -> Inability to recognise objects despite intact perception of basic visual characteristics, usually caused by damage to the ventral stream

Question 47

Gist perception?

Answer 47

- Abstract meaning of a scene is automatically extracted - Takes ~150 milliseconds - Happens before conscious attention can be effectively deployed to explore the scene Based on little information: - Influenced by colour, orientation, crowding/openness - Doesn't necessarily involve object representations or details

Question 48

Scene Layout Perception?

Answer 48

- Similar to gist perception, but takes a few seconds more - After a few seconds, we can perceive the spatial layout of objects in a scene - Repeated layouts are learned implicitly (without awareness)

Question 49

Statistical Estimation/Ensemble Perception?

Answer 49

When there are many objects, the perceptual system can quickly extract "ensemble" properties - Such as mean size, orientation, velocity, direction, facial expressions and more Takes less than 50 milliseconds Possibly related mechanism:we can rapidly estimate the percentage of the group that is a certain colour or orientation

Question 50

Pattern Detection?

Answer 50

- Perceptual system can detect trends or outliers on a graph - Related to ensemble perception - Related to gestalt grouping by proximity Grouped objects are easier to perceive -> reduce clutter

Question 51

Special Perception for Visuomotor Control?

Answer 51

- There may be more accurate perception for motor-planning in the lower visual field - Based on the idea that there are separate perceptual systems for conscious object identification and implicit control of action (e.g. reaching or pointing)

Question 52

Association Formation/Operant Conditioning?

Answer 52

- Rensik mentions a situation in which displays "...help a user move a mouse...[without] awareness of control..." (p.33) - Perhaps this "auto-pilot" can be accounted for by simple habit formation by repetition or operant conditioning - Cross-platform design uniformity achieves this