BHS 499-07Memory and Amnesia

Semantic Long-Term Memory

Semantic Memory

Semantic memory is general knowledge of the world.• Are dogs safe?

• What happens in a restaurant?

Generalizations that can apply to a variety of situations – built from previous experiences.

Semantic Priming

Priming – thinking about one concept brings related memories closer to awareness.• People respond faster to a concept after it has

been primed.

• The prime comes first, then the target (associated item), and response times (RTs) are measured.

Memory Structure

Semantic memory is structured based on shared meaning, not prior associations.• Similar concepts in terms of meaning are

stored closer to each other.

• Semantic “closeness” is metaphoric, based on response times.

Activation spreads to related items. A great deal of repeated use moves

items from episodic to semantic memory.

Controlled Priming

In general, priming is automatic (does not require conscious effort).

Conscious expectations can change priming (Neely).• In the Category Shift Expected condition, the

prime signaled the appearance of a different category which was then primed.

• It took a while for the different expectation to develop so priming occurs after several trials.

Mediated Priming

How far does activation spread during priming?• Lion Tiger Stripes

• Does activation spread to Stripes via Tiger? This phenomenon is called mediated

priming – smaller than regular priming.• The further you go from the original prime, the

smaller the activation and less likely the priming.

Semantic Interconnectivity

No fan effect in semantic memory – more associations speed up, not slow down retrieval.• Direct and indirect connections provide more

ways to retrieve info, making it more reliable.

As with episodic memory, inhibition occurs, but mostly during active retrieval, not when passively reading.

Semantic Memory is Embodied

In addition to capturing abstract relationships among words, storage reflects how we relate to the world.

Concrete nouns tend to activate the sensory cortex because they are things we see and feel – perceptual effort.

Verbs tend to activate the motor cortex because they are things we do.

Categorization

Similarity-based grouping in which two or more entities are treated as equivalent.• Concept – a mental construct that contains

information associated with an idea (a dog).

• Category – a class of concepts to which a set of assertions applies (a dog has four legs, may bite).

Categories are generalized from repeated instances of concepts.

Properties of Categories

Levels of categorization:• Basic, subordinate (detailed), superordinate.

• We operate on the basic level most often – items on that level retrieved better & faster.

Central tendency – there is an averaged ideal or best member of the category.

Graded membership – some members are better than others (robin vs penguin)

Definition of the Category

Categories are defined in different ways:• Rules – things that are used at the beach,

numbers divided by 2, kinship (bachelor).

• Shared features or family resemblance – birds, furniture.

Categories defined by rules or specific features are called classical categories. • Classical theories don’t explain graded

membership and typicality effects.

Prototype Theory

Categories based on similarity or shared features may arise inductively from unconscious mental statistics.• The typical member may be a statistical average of all

category members, called a prototype.

This theory does not explain how categories change over time or how we know their extent.

Caricatures emphasizing distinctive features are better for comparing across categories.

Exemplar Theory

Rather than reasoning from a derived prototype, we use all category members to make decisions.• Explains sensitivity to context effects (priming

of pony mane greater than lion’s mane).

Circularity is a problem • How can members define a category if the

category is needed to identify the members?

Explanation-Based Theory

When a category is formed, people try to explain why its members go together.• Why do wings and feathers go together? Feathers

help creatures to fly.

Ad hoc categories – explanations created for a group of objects (e.g., things that stink).

Psychological essentialism – the items grouped form natural kinds based on their nature, pragmatics, or causality (purpose).

Stereotypes & Prejudice

Stereotypes are categories for various groups of people.• When use of a stereotype causes someone to

treat an individual inappropriately that is prejudice.

Use of stereotypes is natural and part of normal thinking, but we must monitor our use of them for fairness.

Ordered Relations

Semantic Distance Effect – the time it takes to make a judgment is proportionate to their distance.

Semantic Congruity Effect – items are easier to judge when they are similar with respect to some dimension.

Serial Position Effect – items at either end are easier to judge than the middle.

Schemas & Scripts

Commonly experienced aspects of life form schemas – these make it easier to understand new situations.• What happens at a birthday party?

• What happens at a restaurant?

Scripts are schemas with a sequence of events that occur in a stereotyped fashion.• Organized in time, like a script for a play or TV show.

5 Primary Schema Processes

Selection – which components are important and which are peripheral.• Knowing what schema to apply to a situation

tells you what to pay attention to (Droodles).

• Ambiguous passages are clarified by schemas (washing clothes).

Abstraction – the surface form is converted to an abstract meaning.• Drawings change in the direction of meaning.

Schema Processes (Cont.)

Interpretation – We infer missing info during reading or movies based on the schema (e.g., on/off airplane, infer flight)

Integration – When we receive info piecemeal, the schema lets us put it all together (e.g., mysteries).

Reconstruction – fill in gaps at recall from schema (War of the Ghosts).

Scripts

Temporally ordered schemas structured by the main components of the event.• Preference for going in the forward order.

It takes longer to read a script when the next step is further along in sequence.• People scan the steps in the script.

Even when parts are presented in random order they are remembered in proper order.

Limits on Schema Use

Schemas are not always used.• Causes may be inferred from schemas but

not necessarily effects because a number of outcomes may be possible.

When a schema is discredited, people will ignore it.• Escaped convict/deer hunter schema

changed when subjects were told the title was wrong – fewer schema-related intrusions.

Semantic Illusions

How many animals of each kind did Moses take on the ark?• 81% of UCSD students got this wrong.

What was the famous line uttered by Louis Armstrong on the moon?

3 explanations: (1) general focus; (2) partial assessment; (3) similar language components giving illusion it is known.

Naïve Physics

A semantic illusion of nonverbal memory. Mental models of how the world works do not

conform to real life physics.• Similar to Medieval theories of motion.

• Less likely to occur with moving models, more likely with static drawings.

People set thermostat higher so it will heat the house faster – temperature accelerator.

Vision involves emissions from eyes.