Representation of Knowledge - Introduction to Cognitive Psychology - Lecture Slides, Slides of Cognitive Psychology

Download Representation of Knowledge - Introduction to Cognitive Psychology - Lecture Slides and more Slides Cognitive Psychology in PDF only on Docsity! Professor Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 1 Purdue University Representation of knowledge PSY 200 Greg Francis Lecture 23 What is a shoe? Purdue University Concepts   What is the information in Long Term Memory?  May be several different types   We have knowledge about the world  Due to personal experience  Or due to language   Such information must be in some kind of format, which we call concepts   But what are the concepts?  what is the concept of “dog,” “walking,” or “free-market capitalism”? Purdue University Concepts   We will look at three topics in concepts  Definitions (don’t really work)  Prototypes (closer to how humans think)  Exemplars (more likely than prototypes)   And then combinations of concepts  propositions Purdue University Definitions   Plato (and Socrates) spent a lot of effort trying to define terms like virtue and knowledge  they were largely unsuccessful   the 20th century philosopher Wittgenstein wondered if definitions of even simple concepts were possible Purdue University Definitions   Consider the concept shoe, you might define it as Webster’s does  A covering for the human foot, usually made of leather, having a thick and somewhat stiff sole and a lighter top.  Anything resembling a shoe in form, position, or use.   Lots of shoes fit this definition Purdue University Definitions   Consider the concept shoe, you might define it as Webster’s does   A covering for the human foot, usually made of leather, having a thick and somewhat stiff sole and a lighter top.   Anything resembling a shoe in form, position, or use.   But now consider some situations and decide if they are really shoes   A shoe that is intended for display only Professor Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 2 Purdue University Definitions   Consider the concept shoe, you might define it as Webster’s does   A covering for the human foot, usually made of leather, having a thick and somewhat stiff sole and a lighter top.   Anything resembling a shoe in form, position, or use.   But now consider some situations and decide if they are really shoes   a shoe filled with cement, which cannot be worn   a covering worn on the hands of a person without legs who walks on his hands   And this?  Purdue University Definitions   The difficulty is the same one that Plato and Socrates had trying to define virtue   for any definition you come up with, I can find examples that do not seem to fit the definition   But we all know what a shoe is   so our knowledge of this concept must not be based on some precise definition   Note, scientists can (sometimes) create precise definitions (e.g., a dog is defined by a DNA pattern or by mating abilities)   but the definition is somewhat arbitrary Purdue University Prototypes   Perhaps what defines a concept is similarity among its members  there may be no absolutely necessary characteristics  there may be no absolutely sufficient characteristics   Prototype theory supposes that similarity is judged relative to a prototype example of the concept  e.g., an ideal, average, or most frequent version of the concept Purdue University Prototypes   In prototype theory it is possible for an object to be “more” or “less” a certain concept   Consider the concept “coffee cup” Purdue University Prototypes   In prototype theory it is possible for an object to be “more” or “less” a certain concept   Consider the concept “coffee cup”  and variations (some are “cup-ier” than others) Purdue University Prototypes   In prototype theory it is possible for an object to be “more” or “less” a certain concept   Consider the concept “coffee cup”  and variations (some are “cup-ier” than others) Professor Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 5 Purdue University Exemplars   Some coffee cups seem prototypical because they match lots of exemplars  that’s what defines a prototype Purdue University Exemplars   Unlike prototype theory, exemplar theory also contains information about the variability of examples within a concept   Thus, we know that pizzas have an average size of 16 inches but can come in lots of different sizes   And we know that foot-long rulers have an average size of 12 inches, but essentially no variability in size Purdue University Complex associations   How do we represent a concept that involves combinations of concepts?  e.g., “Dogs chase cats.”  e.g., “Last Spring, Jacob fed the pigeons in Trafalgar Square.”   Need to identify the role of each concept Purdue University Propositions   Higher order ideas   things doing something   Statement that is either true or false   things cannot be judged true or false   e.g., Book, Albert, Threw, Professor, Test, Gave  consists of an ordered list of concepts » e.g., (relation:X, Agent:Y, Object:Z) Albert threw the book. (relation:Threw, Agent:Albert, Object:Book) (Threw, Albert, Book) Purdue University Proposition   Network Representation  The proposition connects the appropriate concept nodes threw Albert threw the book Albert book agent relation object Purdue University Proposition   Network Representation   The proposition connects the appropriate concept nodes gave The professor gave a test Professor test agent relation object Professor Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 6 Purdue University Proposition   Network Representation   The proposition connects the appropriate concept nodes chase Dogs chase cats Dog cat agent relation object Purdue University Proposition   Network Representation Jacob Last Spring, Jacob fed pigeons last Spring feeds time agent relation pigeons object pigeons in Trafalgar Square in relation Trafalgar Square location Purdue University Proposition   One way of combining concepts  there are also other theories of how to do this   Used a lot in Artificial Intelligence   Do humans represent interactions of concepts with propositions?   Some experimental evidence Purdue University Proposition   Ratcliff & McKoon (1978)   study phase »  subjects are asked to memorize a set of 504 sentences »  18 - 1 hour sessions!   test phase »  show words and have subjects decide if they were in the study sentences or not » measure reaction time for words from the sentences The bandit who stole the passport faked the signature Purdue University Proposition   Network Representation bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object agent Purdue University Proposition   In the test phase, a word is given and the subject responds as quickly as possible bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport Professor Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 7 Purdue University Proposition   In the test phase, a word is given and the subject responds as quickly as possible bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport Purdue University Proposition   The expectation is that activation will flow through the entire proposition that includes this word bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport Purdue University Proposition   So, if the next word is part of the same proposition, a subject will respond even faster bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object bandit Purdue University Proposition   If words are from different propositions, no priming bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport Purdue University Proposition   In the test phase, a word is given and the subject responds as quickly as possible bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport Purdue University Proposition   Activation will flow through the entire proposition that includes this word bandit stole passport passport stole object relation bandit agent bandit faked signature faked relation signature object passport