Semantic memory is memory for general knowledge, facts, and concepts that are not tied to a particular time and place.
A retrieval cue activates part of the network of associations. Activation spreads along the links to related knowledge.
A schema is a general knowledge structure for typical events or situations.
The memory unit covered how information is stored and retrieved. The knowledge level of the processing pyramid covers how stored information is organized…
The Knowledge Level of the Processing Pyramid
Memory covers how information is stored and retrieved. Knowledge covers how stored information is organized into concepts and into the claims that connect them.
The Knowledge Unit
Concepts and Categories: what a concept is, what a category is, why some members of a category are better examples than others, and how a person decides that a new thing belongs.
Language: the components of language, the rules that combine words into sentences, how a sentence carries meaning, and what a listener adds to it.
Mental Imagery: how the mind re-creates what something looks like and where it is without seeing it, how well that works, and how much people differ in the ability to do it.
Category: A group of things that a person treats as the same because doing so serves a purpose.
Ex: Golden retrievers, pit bulls, and poodles are members of the category “dogs.”
Ex: Steak knife, carving knife, and pocket knife are all in the category “knife.”
Ex: Steak knife, carving knife, and pocket knife are also in the category “things not allowed in your carry-on luggage.”
The same thing can be in several categories. Categorization depends on the purpose!
A Concept and Its Category
The concept is what a person knows about dogs, but the category is the group of animals that knowledge is applied to.
The concept decides which animals belong in the category, but experience with new members can also change the concept.
How a Concept Differs From a Schema
A concept holds what a person knows about one type of thing, but a schema holds what a person knows about a typical event or situation.
A schema contains the concepts that usually appear together in a situation. The restaurant schema contains the concepts of table, menu, server, meal, and check.
The same concept can appear in many schemas. The concept of a table is likely part of your restaurant schema, playing poker schema, and living room schema.
What Concepts Are For
A concept lets a person treat a new thing as a member of a familiar category instead of as something unknown.
Knowing the type tells the person what is usually true of the thing, including facts the person has not checked.
Ex: A shopper who has never seen this exact apple identifies it as an apple and expects it to be edible and to have seeds.
Concepts reduce the processing a new thing requires. This is the Limited Capacity theme applied to knowledge.
Concepts Differ Between People
Concepts come from a person’s experience. Shared language and shared experience produce overlap, but different experiences still lead to different concepts in people’s minds.
Ex: Your concept of a dog and my concept of a dog will have a lot of the same knowledge, but also a lot that is unique to each of us.
Experts represent distinctions that novices do not.
Ex: An experienced birdwatcher’s concept of a bird includes details about beaks, calls, and flight patterns that a novice does not notice.
Poll 1 Results
What the Results Show
The results show which birds and which fruits this class named first.
People name some members of a category before others. Why?
Typicality in Ratings, Verification, and Naming (1973, 1975)
Rips, Shoben, and Smith (1973): Participants decided whether statements such as “A robin is a bird” and “A chicken is a bird” were true.
Finding: Participants verified the statements faster for more typical members.
Rosch (1975): Participants rated how good an example of its category each member was, from 1 (a perfect example) to 7.
Finding: Ratings from different participants agreed with one another.
Finding: The ratings predicted which members participants named first when asked to list the category.
Both studies measure the same difference between members of a category, and the next slide names it.
Typicality
Typicality: The degree to which a member of a category is judged to be a good example of that category.
Ex: Basketball is a more “typical” sport than fishing.
Ex: An apple is a more “typical” fruit than a pawpaw.
Two members can both belong to a category but differ in typicality.
The first question is membership. What makes something a member of the category at all?
The second question is typicality. Why are some members better examples than others?
The polls and the studies so far answered the second question with data. The slides that follow test answers to both questions.
Definitions by Necessary Features
One answer to the membership question is a list of necessary features. Every member has each feature. Anything with all of the features belongs.
Ex: A triangle is a closed figure with three straight sides.
The approach works for categories made by formal rules, but it fails for most everyday categories. It also gives no answer to the typicality question, because every member has the same required features.
Testing a Definition of “Chair”
Try to define a chair by listing the features that every chair must have.
Then test the list. It’s easy to discover “chairs’ that don’t fit:
A beanbag has no legs.
A bar stool has no back.
A wheelchair has wheels.
Any list of required features excludes some things that people call chairs, or it includes some things that they do not.
No Single Feature Holds a Category Together
No one feature appears in every row, but each member shares features with several others.
Overlapping Features Predict Typicality (1975)
Rosch and Mervis (1975): Participants listed the features of 20 members in each of six categories (furniture, vehicles, fruit, weapons, vegetables, clothing). Other participants rated the typicality of each member.
Finding: Members that shared more features with other members of the category received higher typicality ratings.
Finding: The most typical members shared the fewest features with members of neighboring categories.
Typicality comes from overlapping features, but no one defining feature is shared by every member. Overlapping features answer both questions.
Does This Object Belong in the Category “Chair”?
People make this decision in less than a second without looking anything up.
Two models explain how a person stores overlapping-feature knowledge and uses it.
Deciding by Comparison With a Prototype
The prototype model compares the thing with one summary of the category. Greater similarity to the summary is stronger evidence that the thing belongs.
Categorizing by Comparison with a Prototype
Prototype: A mental representation of the most typical member of a category, summarizing the features its members share.
Ex: A bird that is small, feathered, sings, and flies.
Ex: A professor who is older than most of the people who teach you.
Ex: A restaurant with tables, a menu, and a server.
A prototype is a summary, so no real member has to match it exactly.
A prototype summarizes typical features, but it is not always the member that occurs most often (e.g., chicken is not a prototype for the bird category)
Categorizing by Comparison with Exemplars
The exemplar model compares the thing with specific members of the category that the person remembers. The thing belongs to the category whose members it most resembles.
The Exemplar Model
Exemplar: A mental representation of one specific member of a category.
Ex: The neighbor’s beagle, the dog from your favorite picture book as a kid, the German Shepherd that bit you in fourth grade, etc.
Ex: Each professor you have had.
The exemplar model stores separate members rather than one summary.
Exemplars come from a person’s own experience, so two people store different exemplars for the same category.
Prototypes vs. Exemplars
Prototypes compare new items to one “average” example, while exemplars compare them to several remembered examples.
Prototypes are usually faster to use, but exemplars can handle unusual examples more accurately.
Prototypes simplify a category, while exemplars preserve differences between individual members.
Both approaches explain how people recognize and organize things into categories.
Practice: Prototype or Exemplar?
For each one, say whether the person is using a prototype or an exemplar.
“That is not a cookout,” Tasha tells her roommate when the only food on the grill is a tray of burgers, because her idea of a cookout has ribs, sides, and a cooler of drinks.
A couple touring a house agree with the listing that it is a “starter home,” because it matches the small two-bedroom they picture when they hear the phrase.
At 2 a.m., a dorm resident hears a rattle in the hall and decides it is the ice machine, because it sounds like the one she heard the night she moved in.
A barber looks at the photo a new client brought in and calls it a regular fade, because it fits his general picture of a fade.
Choosing a dentist from his insurance list, Connor picks the one whose photo looks like the dentist he went to as a child.
Monique’s mother says the storm on the radar is “like the one in ’09” and starts getting out candles and flashlights.
Practice: Answers
Prototype (Tasha compares the grill to her summary of cookouts in general rather than to one cookout she attended).
Prototype (the couple compare the house with a summary built from many houses rather than with one house they remember).
Exemplar (she matches the rattle to one remembered sound).
Prototype (the barber compares the photo with a summary of fades rather than with one client’s haircut).
Exemplar (Connor matches the office to one specific dentist he remembers).
Exemplar (the mother compares the storm with one specific storm she remembers).
I’m going to show you some pictures. As soon as one appears, everyone say out loud what it is.
The Goldilocks Level
Basic-level category: The level of a category hierarchy that is neither too general nor too specific, which people use by default to name and think about things.
Ex: “car,” between “vehicle” and “Toyota Camry.”
Ex: “cheese,” between “food” and “Swiss.”
Ex: “flower,” between “plant” and “tulip.”
The Basic Level Has the Most Shared Features
Rosch et al. (1976): People wrote down every feature they could think of for various items (“furniture”, “chair”, “recliner”), and the researchers counted the features that most people listed for the same item.
Finding: The basic level (chair) had many more shared features than the level above it (furniture), and the level below it (kitchen chair) added only one or two more.
Studies have also found that when shown a picture, people tend to name it at the basic level, just like our class did with the pictured items.
Children also tend to learn basic-level words first.
The basic level is the Goldilocks level. It is the largest category whose members still look alike, are used alike, and can be pictured as one thing.
Experts Move the Basic Level
Experience sets the basic level, so it differs from person to person.
Ex: To a hairstylist, a client’s hair is “4C,” and to the client’s friend it is “curly.”
Ex: A guitar player who has owned a dozen guitars calls a new one “a Strat,” and a friend calls it “a guitar.”
With enough exemplars, the expert knows as many shared features at the specific level as most people know at the basic level, so the expert’s default name moves down one level.
Practice: Which Level?
For each one, say whether it is at the basic level, above it (too general), or below it (too specific).
Sofia texts her roommate, “there is a spider in the bathroom, come get it.”
After Amara asks for “my nails done,” the nail tech writes “gel French with chrome” on the appointment card.
A sign at the apartment pool reads “No glass containers.”
A two-year-old points at a pony and says “horse.”
Before company arrives, a dad tells his kids to “put your toys away.”
Asked what is biting at the lake, Trey’s uncle says “largemouth,” where Trey would have said “fish.”
Practice: Answers
Basic level (“spider” is the name most people say first; “bug” is too general, and “wolf spider” is more specific than the text needs).
Below the basic level (the nail tech’s experience moves her default to the style name, and the client’s default is “nails”).
Above the basic level (“containers” covers bottles, jars, and cups, which look nothing alike, and the sign uses the general word to cover all of them).
Basic level (“horse” is the level children learn first, and “pony” is more specific than the child knows).
Above the basic level (“toys” covers blocks, action figures, and a ball, which look nothing alike, and the dad uses the general word to cover all of them for this purpose).
Below the basic level (the uncle’s experience moves his default to the species name, and Trey’s default is “fish”).
Edge Cases That Do Not Fit Your Prototype or Exemplars
Typicality is usually enough for us to categorize something. But what about things that are clearly part of a category but not at all typical?
Ex: An ostrich is a bird.
Ex: An audiobook is a book.
Ex: A tiny house on a trailer is a house.
The robin looks like a bird and is a bird. The brick looks like no bird and is not one. Those two are the easy cases. The two magenta boxes are the edge cases of different categories. The ruined lemon does not look like a lemon, but it is one. The counterfeit looks like a dollar, but it is not one. Why? ## How Do We Categorize Edge Cases? (1989, 1991) {.xs}
Keil (1989): Children heard about a raccoon that was dyed black with a white stripe and given a sac of smelly fluid, so that it looked and smelled like a skunk, and then said what it was.
Finding: Young children said it was now a skunk. Older children and adults said it was still a raccoon, because it had been born a raccoon.
Gelman and Wellman (1991): Children said whether a dog with its insides removed, or with its outsides changed, was still a dog.
Finding: Even preschoolers said the dog with its insides removed was no longer a dog, but the dog with changed outsides still was.
In both studies, the animal’s look did not decide the answer, but what was else was known about the animal, like where it came from.
Categorizing Edge Cases with Concept Knowledge
For an edge case, a person uses more than the prototype. The rest of their stored concept knowledge includes what the thing is made of, where it came from, and what it is for.
Ex: The dyed raccoon in Keil’s study is a raccoon because its parents were raccoons (genetics).
Ex: A lemon that has gone brown and moldy is still a lemon because of what is inside the peel.
Ex: A display phone at a store looks like a working phone, but it is not one because it cannot make a call.
The look of the thing is bottom-up data. The concept is top-down knowledge, and for an edge case the top-down knowledge overrules the data.
Edge cases are rare, and people categorize most things by typicality alone.
Categorizing Edge Cases with Purpose
Some categories have no prototype, because the purpose behind them groups things based on a purpose other than appearance.
Ex: rival, fairness, the middle child, etc.
Ex: “Things to sell at a garage sale.”
Category members share a relationship rather than physical characteristics.
Practice: Edge Cases
Each of these is an edge case. For each one, say what in the person’s concept knowledge settles the category: where the thing came from, what it is made of, or what it is for.
A lab-grown diamond passes every test a jeweler can run, but is still worth far less than a natural diamond.
A library checks out an audiobook with no pages and no cover as a book.
At Thanksgiving, a cousin takes a slice of what looks like pumpkin pie; when Tyrese’s grandmother says it is sweet potato, everyone at the table calls it sweet potato pie.
A beanbag with no legs, no back, and no seat is sold in the furniture aisle as a chair.
A puppy born with three legs is still a dog to everyone at the shelter.
A vegan “burger” made from beans and beets is listed on the menu under burgers.
Practice: Answers
Where it came from (every feature a jeweler can observe matches the prototype, but the concept of a natural diamond includes that it formed in the ground).
What it is for (the audiobook matches no feature of the book prototype, but the concept of a book includes telling a story or giving information).
What it is made of (the pie looks like pumpkin pie, but the concept of sweet potato pie includes the filling).
What it is for (the beanbag matches no feature of the chair prototype, but the concept of a chair includes a place for one person to sit).
Where it came from (the puppy matches the dog prototype in fewer features than most dogs, but the concept of a dog includes being born to dogs).
What it is for (the patty matches the burger prototype in shape and place on the bun, and the concept of a burger as a sandwich of a patty on a bun covers it, even though the concept of a hamburger includes beef).
Applying the Core Themes to Concepts and Categories
Mental Representation: A concept is a mental representation of all the knowledge you have about something. A prototype and a set of exemplars are two forms that representation can take.
Bottom-Up and Top-Down Processing: Encounters with members of a category build the concept from the bottom up, but new encounters are also shaped by whatever is stored from past encounters and semantic knowledge, which is top down.
Limited Capacity: A concept lets a person apply stored knowledge to a new thing instead of working out everything about it from the beginning.
Automatic to Controlled Processing: Deciding that a robin is a bird is mostly automatic, but deciding whether a hot dog is a sandwich is more controlled, because the thing is far from the prototype and unlike most exemplars.
Next Time
Language: how sounds, words, and rules let one person share a concept with another.
