Chapter 6nalvarado/PSY335 PPTs/Baddeley/BChap6.pdf · Chapter 6 Semantic Memory and Stored...
Transcript of Chapter 6nalvarado/PSY335 PPTs/Baddeley/BChap6.pdf · Chapter 6 Semantic Memory and Stored...
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Chapter 6
Semantic Memory and Stored
Knowledge
+Semantic vs. Episodic Memory
Declarative memory for general
knowledge and facts lacking
reference to the episodic
context in which it was learned
Examples:
World knowledge
Vocabulary
Rules, formulae, and
algorithms
“Knowing awareness”
Memory for specific events in
context
Comes with a sense of reliving
the event
Called conscious recollection
or “Mental time-travel”
“Self-knowing”
Semantic Memory Episodic Memory
Subjective Differences
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+Semantic vs. Episodic Memory
While all anterograde amnesics have profound deficits in
episodic memory, most have only minor (if any) semantic
impairments:
Spiers, Maguire, and Burgess’s (2001) reviewed 147 cases.
Vargha-Khadem’s (1997) patients, Jon and Beth (impaired as
children but developed normal semantic memories).
Patients with retrograde amnesia often have a selective deficit
in either episodic or semantic memory
Episodic impairment with spared semantic memory:
Tulving’s (2002) patient, KC (intact pre-trauma semantic memory)
Semantic impairment with spared pre-trauma episodic memory:
Yasuda, Watanabe, and Ono’s (1997) patient
Are they really distinct?
Evidence from Neuropsychological Dissociations
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+Anterograde vs Retrograde
Amnesia
Impaired memory
for events after the
trauma
Impaired memory
for events before the
trauma
Retrograde
Anterograde
+Semantic vs. Episodic Memory
Different brain areas are activated for semantic and episodic
memory tasks (Wheeler et al., 1997)
During memory encoding:
More left prefrontal cortical activity for episodic tasks than
semantic.
During memory retrieval:
More right prefrontal cortical activity during episodic memory
retrieval than semantic.
This also suggests that episodic and semantic memory are
different types of memory.
Neuroimaging Dissociations
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+Storing Simple Concepts
Studying the effectiveness of different cues can reveal how concepts are stored in semantic memory.
Which cues lead to faster retrieval of the word “PINAPPLE”?
Initial letters make for better cues than terminal ones:
A FRUIT beginning with “P”?
A FRUIT ending with “E”?
Category cues presented before letter cues show faster retrieval:
A FRUIT beginning with “P”?
A word beginning with “P” that is a FRUIT?
This probably happens because smaller, better-defined categories (e.g. FRUIT) are a more useful starting point than larger, less coherent ones (e.g., words beginning with “P”).
This works best with established categories, not for novices (e.g, Think of a developmental psychologist named “P…”.
Loftus, 1992
✔
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✔
+How is information organized in
semantic memory?
The textbook compares two models:
Hierarchical organization model.
Spreading activation network model.
The spreading activation model better explains some of the
phenomena that are problematic for the hierarchical model:
Familiarity effect
Typicality effect – membership in categories is graded (some items
are better examples of the category than others are).
More typical and more familiar items are recalled faster.
+Conceptual Organization
Semantic memory is organized
into a series of hierarchical
networks.
Major concepts are represented
as nodes.
Properties/features are
associated with each concept.
Cognitive economy rules:
Property information is
stored as high up the
hierarchy as possible to
minimize redundancy.
Hierarchical Network Model
(Collins & Quillian, 1969)
Examples:
• Nodes: Animal; Bird; Fish; Canary
• Features: Has wings; Is dangerous
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+Conceptual Organization
Hypothesis:
Sentences should take more time to process as the number of levels between the tested concept and the features increases.
Task:
Participants had to quickly verify the veracity (truth) of statements.
Results:
Responses to true statements become slower as the separation between the subject and property becomes greater.
Conclusion:
Unless information is directly linked/stored with a concept in semantic memory, we infer the answer from properties of higher nodes.
Making more inferences slows verification.
Hierarchical Network Model
Examples:
• Fast: “A canary is yellow”
• Slow: “A canary can fly”
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http://www.youtube.com/watch?v=kpfsYIN9cZ8
+Conceptual Organization
Problems with the hierarchical network model:
Hierarchical distance is often confounded with familiarity
Controlling for familiarity greatly reduces the hierarchical distance
effect.
Typicality effect: Verification is faster for more representative
member categories, independent of hierarchical distance (Rips,
Shoben, & Smith, 1973).
e.g. “A PENGUIN is a bird” is slower to confirm than “A CANARY
is a bird”.
Typical items have more commonalities with other items in their
category than atypical items.
Categories are fuzzier than Collins and Quillian believed.
Hierarchical Network Model
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+Categorization of Foods
+Categories are organized by dimensions
relevant to item properties.
+Conceptual Organization
Assumes semantic memory
is organized by semantic
relatedness/distance
Measures of relatedness:
“How related are these two
words (e.g. BIRD–
CANARY)?”
“What examples of BIRDs
can you think of?”
The more people that
come up with a particular
member (e.g. CANARY),
the more related they are
Spreading Activation Model (Collins & Loftus, 1975)
Shorter lines
represent
greater
relatedness
From Collins and Loftus (1975). Copyright © American
Psychological Association. Reproduced with permission.
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+Conceptual Organization
Whenever a person encounters or thinks of a concept, that node is activated.
Activation then spreads to related concepts.
Spreading activation decreases as it gets further away from the original point of activation (i.e. weakly related items receive less spreading activation).
Explains the typicality effect
Predicts semantic priming:
A semantically-related word facilitates the processing/identification of a target word
e.g. It is faster to say “BUTTER” is a real word if preceded by “BREAD” instead of an unrelated word like “NURSE” (Meyer & Schvaneveldt, 1976).
Spreading Activation Model
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+Conceptual Organization
Task:
Participants presented with a list of words (e.g. NURSE,
SICK, HOSPITAL, and PATIENT), all of which are related to a
missing target word (e.g. DOCTOR).
Participants are then asked to recognize words they saw
before, including the missing word.
Prediction:
Activation should spread from all the presented words to the
related word (DOCTOR), participants mistakenly recognize
having seen the target word before.
Deese–Roediger–McDermott (DRM) Paradigm
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+Conceptual Organization
Behavioral Results:
Participants tend to mistakenly recognize the missing target
word.
Neuroimaging Results (Schacter et al., 1996)
The pattern and intensity of brain activity was the same for
correctly recognized items as for incorrectly identified, related
words.
Deese–Roediger–McDermott (DRM) Paradigm
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+Conceptual Organization
The spreading activation model is more flexible than
the hierarchical network model.
Pros of flexibility:
The spreading activation model can account for more
empirical findings.
Cons of flexibility:
The flexibility also reduces the specificity of the model’s
predictions, making the spreading activation model more
difficult to test.
Evaluating the Models
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+Organization of Semantic Memory
in the Brain
Semantic memories are represented in the brain as whole objects.
Each object/concept has its own node.
e.g. There’s a special neuron representing your grandmother.
Types of nodes are grouped together (e.g. all living things).
Most evidence suggests that this is not the case.
Different kinds of information
about a given object are stored
in separate brain regions.
e.g. Visual information is
stored in one part of the
brain, while the audio linked
with that object is stored in
another.
This view is becoming
increasingly popular.
“Grandmother” Cell Hypothesis Feature-Based Approach
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+ Organization of Semantic Memory
in the Brain
Neuroimaging Methods:
If thinking about different aspects (visual or auditory) of an object activates the same brain region:
It would support the grandmother cells hypothesis
If doing so activates distinct brain regions:
It would support the feature-based approach
Neuropsychological Methods:
Study individuals with different category-specific deficits and compare the regions of brain damage.
If people with damage to one part of the brain have difficulty identifying living but not nonliving objects, while other patients with damage elsewhere show the opposite pattern:
It would seem to support the feature-based approach
Testing the Approaches
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+Organization of Semantic Memory
in the Brain
Recognition Deficit
Specifically for:
Brain Region Damaged
Living Objects Anterior, medial, and inferior parts of the
temporal lobes
Nonliving Objects Posterior frontal-parietal regions
Neuropsychological Findings (Gainotti, 2000)
Patients tend to have a specific deficit for living objects (80%) rather
than for nonliving objects (20% of patients).
The nonliving objects were generally more familiar than the living objects.
When familiarity was matched, many patients still showed a living object
impairment (Caramazza & Shelton, 1998).
Suggests that concepts are stored in different parts of the brain,
supporting the feature-based approach.
However, this is NOT necessarily true – there are alternative
explanations.
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+Organization of Semantic Memory
in the Brain
Assumptions:
Living things are distinguished based on visual/perceptual features (i.e.
what they look like).
Nonliving things are distinguished based on functional properties (i.e.
what they’re used for).
Based on dictionary entries, there are three times as many visual
descriptors (units) as functional descriptors in the semantic system.
Using a computational model with visual and functional “units”:
Damaging the visual units impaired recognition more for living things.
Damaging the functional units impaired recognition only for nonliving
things.
The theory can potentially explain the neuroscience findings.
Sensory–Functional Theory
(Farah & McClelland, 1991)
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+Organization of Semantic Memory
in the Brain
Type of Processing Brain Regions with the Strongest
ERP Signature at 400 ms:
Visual Fronto-central and anterior–inferior
Functional Occipital, posterior–temporal, and
posterior–parietal
Support for the Sensory–Functional Theory
Sitnikova et al. (2006):
Sensory–functional theory predicts that:
Viewing living things should produce a visual-processing ERP
signature
Viewing nonliving things should produce a feature-processing
ERP signature
Results were as predicted.
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+Organization of Semantic Memory
in the Brain
According to the sensory–functional theory, the distinction is
between sensory and functional properties, not between two
different categories of living vs nonliving objects.
Therefore, perceptual information should be processed in the same
brain region, regardless of whether the object is living/nonliving, as
should functional information (in a different region).
Lee et al. (2002) and Marques et al. (2008) provided
neuroimaging evidence in support of this:
Perceptual processing of both living and nonliving things:
Left posterior inferior temporal lobe regions
Functional processing of both living and nonliving things:
Middle temporal regions
Support for the Sensory–Functional Theory
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+Organization of Semantic Memory
in the Brain
Two properties (sensory and functional) may be too simplistic a
distinction to define all categories.
Many properties of living things aren’t easily defined as either.
Cree and McRae’s (2003) Multiple Feature Approach:
Farah & McClelland argued for a sensory property and a functional
property (what it does or is used for).
Cree & McRae subdivided these two categories into parts:
The sensory property is divided into visual, auditory, taste, and
tactile sensations
The functional property is divided into:
Entity behaviors (what a thing does)
Functional information (what humans use it for)
Limitations of the Sensory–Functional Theory
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+Organization of Semantic Memory
in the Brain
Cree and McRae (2003) identified seven empirical patterns of
category-specific deficits that their approach can explain:
Table from Smith and Kosslyn (2007). Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River,
New Jersey.
Cree and McRae’s (2003) Multiple Feature Approach
Deficit Pattern Shared Properties
Multiple categories consisting of living
creatures
Visual motion, visual parts, color
Multiple categories of nonliving things Function, visual parts
Fruits and vegetables Color, function, taste, smell
Fruits and vegetables with living creatures Color
Fruits and vegetables with nonliving things Function
Inanimate foods with living things Function, taste, smell
Musical instruments with living things Sound, color
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+ Organization of Semantic Memory
in the Brain
The multiple feature approach predicts that each
property is stored in a separate region of the brain
Evidence in favor of this notion comes from Martin and
Chao’s (2001) neuroimaging study:
Category knowledge about color, motion, and shape
activates different brain regions.
Generally, these regions map onto the brain areas
responsible for processing that type of visual information.
Any category with a similarly damaged region of the brain
will be impaired.
Evidence for the Multiple Feature Approach
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+Organization of Semantic Memory
in the Brain
Strengths:
Recognizes that most concepts consist of several properties, not
just two.
Accounts for the different patterns of deficits in brain-damaged
patients.
Consistent with neuroimaging findings suggesting that different
object properties are stored separately.
Still missing:
A complete explanation as to how the different properties of a given
object are integrated rapidly and automatically when needed.
Evaluation of the Multiple Feature Approach
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+Learning New Concepts
Learning in one context does not typically transfer (i.e.
generalize) to other contexts, unless the two situations closely
resemble each other.
According to Barnett and Ceci (2002), transfer is less likely if the two
contexts differ in any of six ways:
Knowledge domain.
Physical context (different environments).
Temporal context (different times).
Functional context (different purposes).
Social context (alone vs. group).
Modality (e.g. visual presentation vs. auditory presentation).
Transfer
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+Learning New Concepts
Factors promoting generalization:
Slower and deeper learning (Schmidt & Bjork, 1992).
Rapid learning is often superficial and specific to the context.
The outline with a different organization promoted more creativity.
Exposing learners to a varied range of examples.
However, it is easier/faster to learn a concept when the examples
are all highly consistent.
A hybrid approach is best to balance efficiency and transfer:
Initial training should focus on consistent examples; once the
concept is learned, additional examples from varied contexts
should be presented.
See Nitsch’s CRINCH and MINGE study
Transfer
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+Crinch ExampleCRINCH – to make someone angry by performing
an inappropriate act, originally used by waitresses.
Varied Context Consistent Context
1. When a man does not remove
his hat on entering a church.
2. When a spectator at a public
event blocks the view of those
behind.
3. When someone flicks cigarette
ash over a polished table.
4. When diners complain about
slow waitress service.
1. When a diner fails to leave a
tip.
2. When diners argue about the
prices on the menu.
3. When a diner deliberately
spills ketchup.
4. When diners complain about
slow waitress service.
Hybrid approach – present the consistent examples first, then the
varied context examples.
+Schemas
Schemas:
Well-integrated chunks of knowledge about the world, events, people, or actions that strongly influence memory.
Schemas serve three purposes:
They allow us to form expectations -- violations of expectations are often memorable and distinctive.
They allow us to draw inferences and fill in gaps when reading or listening to others speak, enhancing understanding.
They allow us to identify indistinct visual images by supplying context.
Schemas in semantic memory include:
Scripts -- knowledge about events and consequences of events.
Frames -- knowledge structures referring to some aspect of the world containing fixed structural information and slots for variable information.
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+A Typical Restaurant Script
73% of respondents reported
these common events when
going to a restaurant:
Sit down
Look at menu
Order
Eat
Pay bill
Leave
48% also included:
Enter restaurant
Give reservation name
Order drinks
Discuss menu
Talk
Eat appetizer
Order dessert
Eat dessert
Leave a tip
Bower, Black, and Turner (1979)
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+Schemas and Visual Scenes
The probability of identifying an object is facilitated when it is in
an expected context and inhibited when the context is
inappropriate.
Contextual match condition:
Kitchen–Bread
No context condition:
No context–Mailbox
Contextual mismatch condition:
Kitchen–Mailbox
Palmer (1975)
Easier
Harder
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+Schemas
There are costs associated with the use of schemas:
Bartlett (1932) presented folk tales, such as The war of the ghosts
to students and then asked them to recall the story.
Students tended to recall stories that were:
Shorter
More coherent
More closely associated with the students’ own perspectives
Especially when their expectations were incompatible with
the story.
Bartlett concluded that intrusions of schematic knowledge caused
systematic errors in recall.
Errors and Distortions
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+Tests of Bartlett’s Theory
Hypothesis:
Schema-driven errors are more likely at longer retention intervals
because schematic information is more durable than rote recall.
Task and Results:
Presented all participants with the same story about a dictator,
whose name was either: Gerald Martin (an unknown) or Adolf Hitler
(someone with associated semantic knowledge).
Asked participants whether they remembered reading a statement
that the dictator “hated Jews,” which did not appear in the story at
two delays:
Short (5 minutes): No difference between groups.
Long (1 week): Participants who read about Hitler were more
likely to incorrectly agree that they had read the statement, having
been influenced by schematic knowledge about the real Hitler.
Sulin and Dooling (1974)
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+Schemas in Everyday Life
Studied schema-driven memory errors in incidental memory, by
walking participants into a naturalistic setting (an office)
In this office were:
Schema-consistent objects (e.g. a desk, calendar, and eraser)
Schema-inconsistent objects (e.g. a skull, a toy top)
Missing from this office were some schema-consistent objects (e.g.
books)
Participants were then surprised with a test asking them to:
First, recall all the objects they could remember
Second, recognize items actually in the office from those that were
not
Brewer and Treyens (1981)
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+Brewer & Treyens (1981)
Books and filing
cabinets were
recalled but were not
present in the room.
+Schemas in Everyday Life
Results:
Participants recalled more schema-consistent than schema-inconsistent items.
True both for items that were present and items that weren’t.
Objects that weren’t present in the room but were recognized with high confidence were uniformly schema-consistent.
Participants recognized more objects than they recalled.
Recalled items were most likely to be objects very consistent with the schema (e.g., typewriter).
Conclusions:
Schemas lead to errors in memory.
Schemas are often used as a retrieval mechanism to facilitate recall.
Brewer and Treyens (1981)
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+Schemas in Everyday Life
People tend to remember information consistent with their own
views better than they remember inconsistent information.
For people with limited knowledge of a controversial subject:
It is easier to add schema-consistent information to the existing
knowledge base.
This is because they don’t have a schema for information contrary
to their view.
For people with a more complete understanding of both sides of an
issue:
It is just as easy to remember information from both sides.
This is because they have schematic support for both sides.
Consistency Bias (Wiley, 2005)
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+Schema Theories Evaluated
Successes:
Schema theories explain why many memories become distorted.
They are strongly supported by evidence showing we possess schemas.
Limitations:
The theories tend to be underspecified, as are the schemas.
Generally can’t predict when we invoke schemas to draw inferences.
Only participants with high reading skills drew predictive inferences
rapidly and automatically (Husband threw vase – infer “break”).
Memory representations are more complex than simple schema theories
predict (e.g., fast food restaurants differ from sit-down restaurants).
They predict that we should make more mistakes than we actually do.
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+Disorders of Concept- and Schema-
Based Memory
Deficit: Examples:
Semantic Dementia:
Difficulty identifying and
describing abstract concepts
for word meanings.
Patients EP and KE
• Find it difficult to
identify/describe the
meaning of common
objects.
• But still able to use the
objects normally.
Goal-directed use of schemas
and scripts.
Problems ordering/assembling
actions within a script, despite
being able to name
appropriate actions.
Associated with damage to
frontal lobe regions.
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+Disorders of Schema-based
Memory
Semantic and sequencing errors made by patients with semantic dementia, temporo-frontal patients, and normal controls. Data from Cosentino et al. (2006).