Week 5 - Semantic Representation

Question 1

What is semantic memory?

Answer 1

Database of what ‘things’ are.

Includes properties or features and its name. E.g. canary is yellow bird, Paris is the capital of France

Question 2

What is conceptual (semantic) knowledge?

Answer 2

The idea of the object plus representation in mind

Question 3

What are the two types of mental representation?

Answer 3

Analogical

Symbolic

Question 4

What us an analogical presentation?

Answer 4

A mental representation that has a direct relationship to the object

It shares some of the physical characteristics of the object.

For example, picture of a violin or cartoon cat.

Question 5

What is a symbolic presentation?

Answer 5

An abstract mental representation.

It does not correspond to the physical features of an object or idea.

For example, the word “violin” or “cat”.

Question 6

What did Kosslyn et al (1978) study indicate about mental imagery?

Answer 6

Study used eye-tracking movements to observe participants looking at a map.

Demonstrated that participants spent more time than required to scan distances between two visual images that they knew to be longer

This was true even when the same amount of material falls between the initial focus point and the target.

Indicates that mental imagery can function as an internal spatial medium.

Question 7

Which is a more useful representation type - symbolic or analogical and why?

Answer 7

Symbolic.

Are more suited to represent concepts than analogical representations, because of their flexibility

Question 8

What is a concept?

Answer 8

The mental content of some object or event.

All the knowledge one has about that category, e.g. cats have whiskers, four legs, a tail.

Question 9

What is a semantic classification?

Answer 9

Basic units of semantic memory,

Question 10

What is a mental lexicon?

Answer 10

Single words and their meaning,

Question 11

What are semantic association networks?

Answer 11

A set of concepts that are related to one another. Useful for remembering, guiding behaviour, reasoning and problem-solving.

Question 12

What does categorization mean?

Answer 12

Grouping things based on shared properties; reduces the amount of knowledge we have to hold in memory, ex: musical instruments.

Thought of as the external content related to the concept.

Question 13

What does Ross & Murphy’s (1999) sorting task tell us?

Answer 13

Context important for categorisation.

Question 14

What does Barsalou (1983) say about categories?

Answer 14

Goals and purposes are important to define categories

Question 15

What are the two dominant models on how categorisation occurs?

Answer 15

Classical and Prototype model of categorization

Question 16

What is the Classical View (aka - Defining attribute model) of categorisation?

Answer 16

The idea that a concept is characterized by a list of features that are necessary and sufficient to determine if an object is a member of the category.

Question 17

According to the classical view that are the two conditions for something to belong to a category?

Answer 17

o Necessary: each feature must be present

o Sufficient: If each feature is present that’s all you need to belong to that category

Question 18

What is the significance for categorisation if the two conditions must be present?

Answer 18

o Membership within a category is an all-or-none basis
o All of category’s attributes equally important in defining that category
o All members of a category are equal in category membership

Question 19

What is the main criticism for this classical view of categorisation?

Answer 19

Typicality effect: finding that people are quicker to make category judgments about typical members of a category than atypical members.

Question 20

What did Rips et al, (1973) find about categories?

Answer 20

Participants had slower reaction times when making a category judgment for “penguin is a bird” compared to “robin is a bird”

Question 21

What did Rosch & Mervis (1975) say about categories?

Answer 21

Some members are “more members” than others

Question 22

What is the Prototype Model of categorisation?

Answer 22

o Within each category, some members are more representative than others.
o Membership defined on the basis of a ‘typical’ or ‘likely’ set of features,

Question 23

What is the main difference between prototype model and classical view of categorisation?

Answer 23

Unlike classical view, doesn’t require the possession of all characteristics. Allows for more flexibility in concept formation

Question 24

What is the main criticism of prototype model?

Answer 24

Some concepts are not flexible and require more definition. Determined by definition rather than similarity (e.g., “triangle” or “even number”).

Question 25

What is the problem with the typically effect and in the prototype model?

Answer 25

Typicality is sensitive to context - two objects may have the same level of typicality but one may be more suited for certain contexts compared to the others). Category of ‘bird’ more likely to be given to chicken if seen in a farm than a city scene

Question 26

Which categorisation model better decribes categorisation process?

Answer 26

Not all categorization processes are the same. Some concepts may be better described by classic view, other by prototype.

Question 27

How are semantic representations in the brain stored and organised?

Answer 27

Distributed View: general agreement that knowledge of objects and concepts is widely distributed in the brain.

Question 28

How are semantic representations activated in the brain?

Answer 28

Concepts are a collection of properties (features), which activate different areas

Question 29

What evidence is there that supports distributed view?

Answer 29

Evidence from brain-damaged patients with category-specific deficits indicates that different object properties are stored in different brain areas.

Question 30

What does the distribution-only theory suggest?

Answer 30

No specific hub for semantic knowledge. Concepts are described by perceptual and functional attributes that involve independent brain areas that are interconnected Action, perception, language, motor areas can be activated during processes of concepts but there is no single ’core area’ responsible

Question 31

What does the distribution + plus hub theory suggest and why?

Answer 31

View that semantic memory is distributed BUT is underpinned by an ‘amodal’ hub for semantics, residing in the anterior temporal lobe (red area). Modality-specific areas are interconnected but communicate ‘through’ a semantic hub.

Question 32

Why does Patterson et al (2007) argue that the semantic hub is necessary?

Answer 32

Modality specific processes cannot account for why we are able to make higher-order generalisations. For example, scallops and prawns have similar conceptual overlap, yet we are able to make specific distinctions between them. Indicates higher-order function.

Question 33

What predictions does distribution-only theory make about semantic impairments?

Answer 33

No such generalized semantic impairment, since modality-specific aspects of the concept reside in different areas. For example, semantic memory of the sounds of the concept would be impaired but not the picture of the concept

Question 34

What predictions does distribution-plus-hub theory make about semantic impairments?

Answer 34

Predicts that lesions to ‘the hub’ will lead to general, amodal, semantic impairments. For example, objects, sounds, pictures, words associated with that concept would be impaired,

Question 35

What does acquired disorders of semantic memory tell us about conceptual knowledge?

Answer 35

All four conditions give useful clues about the nature and organization of conceptual knowledge, but from different angles

Question 36

What does semantic dementia tell us about conceptual knowledge?

Answer 36

Shows deficits across all semantic modalities and virtually all concepts (except numeric representations). Leads to the disruption of semantic representations. E.g. Semantic deficits for producing and comprehending semantic vocabulary. Evidence from picture categorisation tasks, colour and object recognition tasks and delayed copying tasks suggest cross-modal impairment. Progression of disease correlated with degrees of impairment in task performance.

Question 37

What does Alzheimer’s disease tell us about conceptual knowledge?

Answer 37

Semantic memory is frequently affected in but typically at a later stage and to a more modest extent than episodic memory.

Question 38

What does Herpes simplex virus encephalitis (HSVE) tell us about conceptual knowledge?

Answer 38

Demonstrates category-specific semantic deficits. HSVE causes lesions to the antero-medial temporal lobe. Semantic deficit in HSVE is often category-specific, with relatively well preserved knowledge of man-made things but impaired knowledge of living things. Patients have category-specific difficulties with living things rather than non-living things (e.g. naming and drawing). Debate in literature if category specific deficits indicate sepea

Question 39

What does Stroke tell us about conceptual knowledge?

Answer 39

Stroke causes semantic Aphasia (SA) but not the same as semantic dementia (SD) Both lead to anomia - poor performance on naming tasks. SA suggests loss of access to semantic representations. No impairment to ATL SD there is an actual loss of these representations. Impairment to ATL

Question 40

Where is the semantic hub thought to reside and how do we know?

Answer 40

In the anterior temporal lobe (ATL). We know this because semantic dementia (SD) is characterized by focal lesions in the anterior temporal lobes (ATL). Semantic dementia patients show a general semantic impairment, for every category of concepts across modalities. HSVE patients have impairment in the antero-medial temporal lobe. Stroke - anomia but no impairment to ATL. SD - anomia plus ATL impairment.

Question 41

What is Anomia?

Answer 41

The failure to name objects, concepts and people, whether in response to stimulus presentation or in spontaneous speech.

Question 42

What are the main differences between the performance on semantic tasks by stroke patients and patients with semantic dementia?

Answer 42

SD: benefit from ‘cueing’ e.g. they fail to name a lion from a picture, but if given the cue “L” they could probably name it correctly ``` Make associative (semantic) errors. Asked to name ‘milk’, they say ‘cow’ ``` SA: Do not make associative errors or benefit from semantic facilitation, like cueing

Question 43

What does gradual loss tell us about semantic knowledge?

Answer 43

Gradual loss: Concepts deteriorate gradually, with some aspects of their meaning being lost before others Evidence from Patient JL: Naming responses of living and non-living things deteriorated over time Less able to give specific name over time

Question 44

What does partial loss tell us about semantic knowledge?

Answer 44

Loss of some aspects of meaning but not others, suggests concepts are represented as collections of properties or features of different category type. Evidence from patients with semantic memory disorders Indicates that concepts are not mental atoms. Otherwise they would be lost all at once.

Question 45

What are category-specific semantic deficits?

Answer 45

Brain damage affects certain categories of concepts and not others. Problems most often with living things. Problems with non-living things much rarer. Evidence from patients with HSVE, for example, patient RC: category-specific difficulties with living things rather than non-living things (e.g. naming and drawing)

Question 46

What does neuropsychological evidence indicate about category-specific deficits and the semantic hub?

Answer 46

Category-specific regions in posterior areas Category-specific deficits: evidence for independent neural systems to process modality-specific information. The anterior temporal lobe (ATL) is the region where the amodal semantic memory is localized

Question 47

What does "temporal cortex lesion" studies tell us about category-specific regions?

Answer 47

Pobric et al. (2010) found that temporarily disrupting activity in the (ATL) and (IPL) causes specific impairments. Anterior Temporal Lobe (ATL) - impairment to category-general naming (living things, tools) Inferior Parietal Lobule (IPL) - impairments to naming man-made objects (tools – processing of praxis)

Question 48

What is ATL?

Answer 48

The anterior temporal lobe (ATL) is the region where the amodal semantic memory is localized Pobric et al. (2010) found that temporarily disrupting activity in the ATL causes category-general impairments,

Question 49

What is ITL?

Answer 49

Pobric et al. (2010) found that temporarily disrupting activity in the ITL causes category-specific impairments. Other modality-specific areas underpin specific modalities (e.g. motion). Modality-specific regions like IPL provide the basic “ingredients” (sensory, motor, verbal etc.), while the ATL supports an additional amodal representation.  Recent evidence suggests the ATL is graded.

Question 50

What is ATL Important for?

Answer 50

Anterior temporal lobe is important for semantic representations, i.e., the content of semantic knowledge.

Question 51

What are Prefrontal and Temporo-parietal areas important for

Answer 51

Prefrontal and Temporo-parietal areas are important to access and manipulate semantic representations