Historical Foundations of Cognitive Psychology Cognitive Psychology • Tim Curran • A Definition • [email protected] – The scientific study of mental processes such as perceiving, remembering, using language, • Lecture slides are available at: reasoning, and solving problems. http://psych.colorado.edu/~tcurran/oreilly.html • The formal discipline of “Cognitive * BUT YOU SHOULD STILL TAKE NOTES! Psychology” started in the mid-1900’s. • Read Chapter 1 in Text • It’s roots can be traced back much further. Later Philosophy Greek Philosophers (1600s - 1800’s) (4th-5th Century BC) • Nativism (since Plato) – Knowledge is innate – Influential figures: Plato & Aristotle • heredity, nature – Began to consider questions about perception, memory, • Empiricism and thought. – Influential figures: Hobbes & Locke • Plato = Rationalist – Knowledge is gained through experience – Emphasized logical analysis. • Aristotle = Empiricist • learning, nurture – Emphasized observations of the external world. – Associationism – Specific assumptions, allowing for tractable questions: • Knowledge originates from interconnected information. • The world can be understood and predicted. – BANNANA-YELLOW-FRUIT-PEEL-LONG • Humans are part of that world. • Key principle of modern “neural network” models. • Explanations should be of this world. • Compromise Positions – Influential figures: Descartes & Kant – Both Nurture and Nature are important. Influence of Philosophy on German Physicists Cognitive Psychology (1800s) • Influential figures: • Contribution to Cognitive Psychology • Helmholtz: Color vision – Identified many fundamental questions and • Fechner: Psychophysics assumptions about the nature of the mind. • Relationship between physical changes in stimuli and sensory experience. • Limitations • Applied scientific methods. – Lacked scientific methods. • Contribution to Cognitive Psychology • Use of scientific/experimental methods. • Limitation • Limited to the study of simple sensory processes. Early Scientific Psychology Structuralism • Influential figure: Wilhelm Wundt • Structuralism • Focus on identifying the basic building blocks of conscious experience. • Functionalism • Analogy with periodic table of elements in chemistry. • Behaviorism • Main method: "Introspection" under controlled conditions. • Contribution to Cognitive Psychology – Emphasized systematic, controlled observation. – Importance of the understanding the structure of the mind, and higher cognitive processes. • Limitation – Reliance on introspection. Behaviorism Functionalism • Influential figures: John B. Watson, B. F. Skinner • Influential figure: William James • Guiding Principles: – Only focus on that which is observable. • Mental processes must be adaptive, so what are – Explain behavior; not thought, consciousness, etc. they good for? – Theories should be simple. – e.g., practical uses and functions – Break down behavior into irreducible constructs. • Main method: Rigorous experimentation – Inspired by evolutionary theory. • • Main methods: Contribution to Cognitive Psychology – Introspection, questionnaires, mental tests, animal – Emphasis on rigorous experimentation. experiments – Powerful theories of learning • Contribution to Cognitive Psychology • Classical Conditioning – Learning relationships among stimuli. – Emphasis on the functions and applications. – e.g., Pavlov’s dog learned relationship between bell and food. • Limitation • Operant Conditioning – Methods not very rigorous. – Learning responses that are rewarded. – e.g., A dog learns to sit for a treat. • Failure to consider intervening mental processes Limitations of Behaviorism – Behaviorism: Stimuli Responses • Failures to account for aspects of human behavior – Cognitive Psychology – Over-emphasis on animal experimentation – Language Stimuli Mental Processes Responses • Skinner suggested language was learned through basic principles of operant conditioning. – Stimulus (memorize this list) – i.e., we learn to say what is rewarded • lion, onion, Bill, firefighter, carrot, • Fails to account for Generativity of language. zebra, John, clerk, Tim, nurse, cow – The creation of novel utterances that have never been rewarded in the past. – Response (recall) – e.g., Chomsky (linguist) • lion, zebra, cow, onion, carrot, firefighter, clerk , nurse, John, Bill, Tim – Mental Processes • Strategies, grouping, reorganization, etc. Overview of Different Approaches Stimuli Mental Processes Responses Outside Influences in mid 1990’s •Philosophy •Argue about mental processes • Interest in optimizing human performance •Introspection – World War II •Directly tap into mental processes • Computer Science •Behaviorism – Artificial Intelligence •Study stimulus-response relationships – Computer Metaphor •Ignore mental processes • Information processing, memory buffers, etc. •Cognitive Psychology •Study stimulus-response relationships •Make inferences about mental processes Information Processing Analysis Example Information Processing • The dominant approach toward studying human cognition. • Decomposing a cognitive task into a set of abstract information processing steps. • Designing experiments to understand the characteristics of each stage. Representations & Processes Sternberg’s Memory Scanning Task • A representation is a symbol for an entity in the real world. – e.g., computers represent numbers in a binary code • “8” = “0-1-1” • A process manipulates/transforms representations in some way. – e.g., addition, multiplication, etc http://coglab.psych.purdue.edu/coglab/ Information Processing Stages Possible Search Processes in the Memory Scanning Task 1. Serial, Exhaustive Search – Whole letter set is always searched, one by one. Search • RT increases with set size, and Yes = No Encode Decide Respond Memory L AKLM L Yes = / ? No = z AKLM (stages during probe recognition phase) Possible Search Processes Possible Search Processes 2. Serial, Self-terminating Search 3. Parallel Search – Letters searched one by one until target is found or – All letters in set simultaneously identified. search is complete. • RT increases with set size, but faster for “yes” responses • RT unaffected by set size or yes/no. because search stops when the target is found in the set. Encode Search Decide Respond Summary of Information Sternberg’s Results Processing Approach • Decomposing a cognitive task into a set of abstract information processing stages. • Serial Exhaustive Search • Attempts to understand – Search rate inferred from slope = 38 ms per item processes/representations within each stage. • Encoding/Decision/Response • A given stage (e.g., memory search) can be Stages – Combined speed is y-intercept studied by manipulating variables (e.g., set = 397 ms size) hypothesized to affect that stage, and – Don’t vary with set size observing performance (e.g., reaction time). – Vary with variables that should affect these processes..