Structure of Semantic Memory Background on Semantic Memory The Feature Comparison Model The Prototype Approach

1. Structure of Semantic Memory
Rohini V. S.
Assistant Professor
Department of Psychology
St. Mary’s College ,Thrissur

2. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
Background on Semantic Memory
 Semantic memory is our organized knowledge about the world.
 Semantic memory includes:
o encyclopedic knowledge (e.g., “Martin Luther King, Jr., was born
in Atlanta, Georgia”);
o lexical or language knowledge (e.g., “The word justice is related to
the word equality”);
o conceptual knowledge (e.g., “A square has four sides”).
 It influences most of our cognitive activities. For instance, we need this
form of memory so that we can determine locations, read sentences, solve
problems, and make decisions.

3. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
Categories and concepts are essential components of semantic memory.
 Category
Set of objects that belong together.
For example, the category called “fruit” represents a certain
category of food items; the cognitive system treats these objects
as being equivalent.
 Concept
Mental representations of a category.
Eg:- Concept of “fruit,” which refers to your mental
representation of the objects in that category.
Background on Semantic Memory

4. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
The Feature Comparison Model
 According to the feature comparison model, concepts are stored in
memory according to a list of necessary features or characteristics.
 Smith and his coauthors propose that the features used in this model
are either defining features or characteristic features.
o Defining features are those attributes that are necessary to the
meaning of the item.
o For example, the defining features of a robin include that it is
living and has feathers and a red breast.
o Characteristic features are those attributes that are merely
descriptive but are not essential.
o For example, the characteristic features of a robin include that it
flies, perches in trees, is not domesticated, and is small in size.

5. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
Research on the Feature Comparison Model:
 Sentence verification technique.
o In this technique, people see simple sentences, and they must
consult their stored semantic knowledge to determine whether the
sentences are true or false.
(eg: A poodle is a dog, a squirrel is an animal, a flower is a rock,
etc.)
One common finding in research using the sentence verification
technique is the typicality effect.
o Typicality effect: People reach decisions faster when an item is a
typical member of a category, rather than an unusual member.
The Feature Comparison Model

6. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
The Prototype Approach
According to Eleanor Rosch, we organize each category on the basis of
a prototype, which is the item that is most typical and representative of
the category.
 You decide whether an item belongs to a category by comparing that
item with a prototype.
For example, you conclude that a sparrow is a bird because it
matches your ideal prototype for a bird.
 Rosch (1973) also emphasizes that members of a category differ in
their prototypicality, or degree to which they are prototypical.
A robin and a sparrow are very prototypical birds, whereas
ostriches and penguins are non-prototypes.

7. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 A category tends to have a graded structure, beginning with the
most representative or prototypical members and continuing on
through the category’s non-prototypical members.
 Characteristics of Prototypes:
o Prototypes are supplied as examples of a category.
o Prototypes are judged more quickly after semantic priming.
(Semantic priming effect means that people respond faster to an
item if it was preceded by an item with similar meaning. For
example, you would make judgments about apples more quickly
if you had just seen the word fruit than if you had just seen the
word giraffe.)
The Prototype Approach

8. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
o Prototypes share attributes in a family resemblance category.
(Family resemblance means that no single attribute is shared by
all examples of a concept; however, each example has at least one
attribute in common with some other example of the concept.)
Levels of Categorization
 Superordinate-level categories.
o They are higher-level or more general categories.
Eg: “Furniture,” “animal”, “tool” etc.
 Basic-level categories.
o They are moderately specific.
Eg:“Chair,” “dog”, “screwdriver” etc.
The Prototype Approach

9. The Prototype Approach
 Subordinate-level categories.
o They refer to lower-level or more specific categories.
Eg: “Phillips screwdriver”
Structure of Semantic Memory, Rohini V. S., St. Mary’s College

10. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 The exemplar approach argues that we first learn some specific
examples of a concept; then we classify each new stimulus by deciding
how closely it resembles those specific examples.
 Each of those examples stored in memory is called an exemplar.
o Eg: concept of “dog” would be represented by numerous examples
of dogs you have known.
o In contrast, the prototype approach would argue that your prototype
of a dog would be an idealized representation of a dog, with
average size for a dog and average other features—but not
necessarily like any particular dog you’ve ever seen.
The Exemplar Approach

11. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 The network models of semantic memory propose a netlike organization
of concepts in memory, with many interconnections.
Eg: The meaning the concept, “apple,” depends on the concepts to
which it is connected.
The Collins and Loftus Network Model
 Semantic memory is organized in terms of netlike structures, with
numerous interconnections. When we retrieve information, activation
spreads to related concepts.
 Each concept can be represented as a node, or location in the network.
 Each link connects a particular node with another concept node.
 The collection of nodes and links forms a network.
Network Models

12. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 When the name of a concept is mentioned, the node representing
that concept is activated.
 The activation expands or spreads from that node to other nodes with
which it is connected, a process called spreading activation.
 Frequently used links have greater strengths. As a result, activation
travels faster between the nodes.
Network Models

13. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 ACT- Automatic Components of Thought.
 According to Anderson (1990), the meaning of a sentence can be
represented by a propositional network, or pattern of interconnected
propositions.
 A proposition is the smallest unit of knowledge that can be judged
either true or false.
Eg: the phrase “white cat” does not qualify as a proposition
because we cannot determine whether it is true or false.
 Each of the concepts in a proposition can be represented by its own
individual network.
Anderson’s ACT Theories
Network Models

14. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 Similar to Collins and Loftus’s (1975) model, Anderson says that,
the links between nodes become stronger as they are used more often.
 At any given moment, as many as ten nodes are represented in the
working memory.
 Activation can spread. However, the limited capacity of working
memory can restrict the spreading.
Network Models

15. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 Cognitive processes can be represented by a model in which activation
flows through networks that link together a large number of simple,
neuron-like units.
 Two other names—connectionism and neural networks—are often
used interchangeably with PDP approach.
 Takes into account the physiological and structural properties of
human neurons.
The Parallel Distributed Processing Approach
Network Models

16. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
 Three central characteristics of the PDP approach:
1. Cognitive processes are based on parallel operations, rather than
serial operations. Therefore, many patterns of activation may be
proceeding simultaneously.
2. A network contains basic neuron-like units or nodes, which are
connected together so that a specific node has many links to other
nodes.
3. a concept is represented by the pattern of activity distributed
throughout a set of nodes
Network Models

17. Structure of Semantic Memory, Rohini V. S., St. Mary’s College
REFERENCE
 Matlin, M. W.(2009) Cognition. 7th Edition. John Wiley & Sons,
Inc. USA