PSYU2239 Lecture 12: Semantic Memory

What is the difference between episodic and semantic memory?

Episodic memory involves personal events in time and place; semantic memory is general world knowledge and not tied to specific experiences.

Which brain regions are linked to episodic vs semantic memory?

Episodic: hippocampus; Semantic: lateral and anterior temporal lobes.

What is a sentence verification task?

Participants judge the truth of sentences (e.g., 'A canary is a bird'), used to study semantic memory structure via RT.

What do typicality effects reveal in sentence verification?

People respond faster to more typical examples (e.g., 'A robin is a bird' faster than 'A penguin is a bird').

What does the Hierarchical Network Model (Collins & Quillian, 1969) propose?

Concepts are structured in hierarchies, with properties stored at the highest applicable level to save memory.

What are limitations of the Hierarchical Network Model?

Fails to explain typicality effects, negative judgments, and inconsistencies in RTs that don't follow hierarchy.

What is the Spreading Activation Model (Collins & Loftus, 1975)?

Concepts are linked by associative strength; activation spreads from one concept to related

Concepts are linked by associative strength; activation spreads from one concept to related

Typicality effects, semantic priming, and graded category membership.

What is the semantic priming effect?

Faster recognition of a word (e.g., 'truck') when preceded by a semantically related word (e.g., 'car').

Which model explains semantic priming?

Spreading Activation Model.

What is the Feature Comparison Model (Smith et al., 1974)?

Concepts are represented by sets of defining and characteristic features compared in two stages.

What are the two types of features in this model?

Defining features (essential) and characteristic features (common but not essential).

What are criticisms of the Feature Comparison Model?

Difficult to distinguish between defining and characteristic features; poor at explaining hierarchical inference.

What is a category-specific semantic deficit?

Selective impairment in knowledge for one category (e.g., living things) while retaining others (e.g., tools).

What did Patient JBR show?

Impaired knowledge of living things and some inanimate categories, but preserved knowledge of non-living objects.

What is the Perceptual-Functional Theory?

Living things are represented by perceptual features; non-living things by functional features.

What is a criticism of the Perceptual-Functional Theory?

Not all deficits align with perceptual vs. functional distinctions; some properties fall outside this split.

What is the Distributed-plus-Hub theory?

A theory of semantic memory that explains how we represent and understand concepts. Proposes that concepts are represented across two systems: 1. Spokes – Modality-specific features (e.g., visual, auditory, tactile, motor) stored in distributed brain regions. 2. Hub – An amodal, integrative structure in the anterior temporal lobe (ATL) that binds these features into coherent concepts.

What is the function of the 'hub' in this model?

Integrates features from multiple modalities into a unified concept.

What is evidence for the hub in the ATL?

Semantic dementia and TMS disruption to ATL impair conceptual knowledge across categories.

What did the 'conceptual lemon' study (Chiou et al., 2014) find?

Transcranial magnetic stimulation (TMS) to Anterior Temporal Lobe (ATL) eliminated the color congruency effect in object naming, supporting ATL’s role as conceptual hub.

What is the color congruency effect?

Faster recognition of objects when shown in their typical (canonical) color.