What is Cognitive Science by samc


									What is Cognitive Science?
… is the interdisciplinary study of mind and intelligence, embracing philosophy, psychology, artificial intelligence, neuroscience, linguistics, and anthropology

(Stanford Encyclopedia of Philosophy)

Practical Value
• Education:
– Intelligent tutoring systems – Automatically grading exams

• Legal:
– Distinguishing between true and false memories – Evaluating line-ups

• Sales
– Understanding beliefs and desires

• Information technology:
– Search engines – Building intelligent systems

Most cognitive scientists are cognitive psychologists, computer scientists, or cognitive neuroscientists

(from: Schunn et al. 2005)

Understanding Computation Computer Science/ Artificial Intelligence To understand how the brain works

Interdisciplinary study of intelligent behavior
To understand limits of theories Philosophy Cognitive Science


For human data in various tasks Experimental Cognitive Psychology

To understand structure of language


We will focus mostly on insights from Cognitive Psychology

Areas of Study
• Cognition is about internal processes that are often unobservable, e.g.: Perception, Attention, Memory, Visual Imagery, Language, Concept Learning, Reasoning


• Need converging evidence from different perspectives to really understand cognitive processes

Levels of Analysis
• Implementation:
– Where does mental activity take place in the brain? – How is processing actually done with neural activity?

• Algorithm:
– What is the abstract representation for input and output? – What stages are used to process information? – (Information processing level)

• Computation:
– Why does the algorithm work well? – What is the goal or purpose of the computation?

(Marr, 1982)

Levels of Analysis Example

Information Processing
• Information processing models resemble processing in computers – made cognitive psychology popular • Information made available by the environment is processed by a series of processing systems • Processing system is a set of processes that work together to accomplish a type of task, using and producing representations as appropriate • The major goal of research is to specify these processes and representations

Types of Processing
• • • • Bottom-up processing Top-down processing Parallel processing Serial processing

An early version of the information-processing approach  purely bottom up or stimulus-driven

A Demonstration of Top-Down Processing

Top-down processing: perception affected by knowledge of world

Why do we seem to have a fairly robust interpretation of which shapes are concave and convex when the perceptual information is perfectly ambiguous? -> perception affected by knowledge
(Kleffner & Ramachandran, ’92)

Top down processing: perception affected by memory

• First time, sine wave speech sounds incomprehensible (to most) • After hearing the natural utterance, perception of sinewave speech seems to be quite different


http://psiexp.ss.uci.edu/research/teachingP140C/demos/naturalutterance.aif (for more info: http://www.haskins.yale.edu/haskins/MISC/SWS/SWS.html)

"The steady drip is worse than a drenching rain."

Sound Induced Illusory Flashes
• Example of parallel and interactive processing: visual perception affected by auditory perception • http://www.cns.atr.jp/~kmtn/soundInducedIllusor yFlash2/

Top-down processing

Later stages of processing affect earlier stages
 can explain effects of Knowledge, memory, expectations and context

Parallel vs. Serial Processing
• To illustrate the difficulty of distinguishing between serial and parallel processing, consider the Sternberg task • Goal: what steps are involved in comparing information to memory? How long do these steps take? • Task:
– give subjects memory sets. E.g. 3 9 7 – Probe memory with targets and foil digits: 9 = “yes”, 6=“no”. Measure reaction time. – Vary the size of these memory sets

Typical Sternberg Results
• Plot reaction time as function of memory set size and type of trial (targets/foils) • What are the implications of seeing a linear increase in reaction time as a function of memory set?

A serial information processing model for Sternberg task


Perceive Stimulus

Is it a 3?

Is it a 9?

Is it a 7?

Make Decision


This serial information processing model predicts a linear increase

A parallel information processing model for Sternberg task
Is it a 3? Perceive Stimulus


Is it a 9?

Make Decision


Is it a 7?

This parallel information processing model also predicts a linear increase

• Identifiability refers to the ability to specify the correct combination of representations and processes used to accomplish a task • Sometimes, behavioral results do not allow processes and representations to be uniquely identified (e.g. Sternberg task) • Need converging evidence to tell theories apart – More behavioral data – Data from cognitive neuroscience – Data from neuropsychology

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