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Cognitive Psychology: Marielle Lange 1. What is Cognitive Psychology?

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1 Cognitive Psychology: Marielle Lange 1. What is Cognitive Psychology?

2 General points n I have a French accent + I tend to speak fast I will do my best to speak at a decent rate. If I don’t, do not hesitate to ask me to speak more slowly. n A copy of the slides will be posted on the web after each lecture. n No notes before classes

3 Course Books Eysenck, M. W. and Keane, M. T. (1995). Cognitive Psychology: A Student's Handbook. Hove: LEA. 3rd Edition. [E&K] Recommended: Anderson, J. R. (1995). Cognitive Psychology and its Implications. New York: W. H. Freeman. 4th Edition. Sternberg (2003). Cognitive Psychology. Thompson. for this lecture: E&K, chapter 1 for next lecture: E&K, chapter 5

4 Course structure 1. What is Cognitive Psychology? 2. Attention and Focus 1: focused attention 3. Attention and Focus 2: split attention 4. Object recognition 1: recognising patterns & words 5. Object recognition 2: recognising auditory stimuli 6. Cognitive Representations: Paivo’s dual- route hypothesis

5 Aims of the course Demonstrate that cognitive psychology is an approach, not a specific set of experiments Show you how different types of evidence are used to evaluate theories, in cognitive and other branches of psychology Illustrate with evidence from four major domains (attention, vision, language, knowledge representation)

6 History 1879 Establishment of first psychology laboratory (George Wundt, Leipzig, Germany) – Structuralism 1890 Armchair psychology (e.g., James, 1890)

7 © Both structuralism and functionalism referred to mentalistic contents of mind that could not be directly observed. Participants (or researchers) are not always aware of the procedure they follow to perform a task (can you tell me how you do to remember something?). Problems with the early - introspective - methods… Problems with the early - introspective - methods…

8 Behaviourist’s reaction …to stick to the only thing we can study objectively: the behaviour that follows an input. …and to avoid to introduce mental variables (or unseen variables) to explain behaviour. ©

9 Behaviourist Psychology 1920s Behaviourist Psychology (derived from learning theory) “[The behaviourist] dropped from his scientific vocabulary all subjective terms such as sensation, perception, image, desire, purpose, and even thinking and emotions as they were subjectively defined.” (Watson, 1930) Black box metaphor (Skinner?).

10 Times of change Von Neuman (1950) n Computer: Representations and processes (memory, processing system) between input (key presses) and response (screen display). n Computers: y Process information in complex ways y Store lots of information in memory y Retrieve information from memory and use it y Have an input and an output y Have hardware and software y Have limited capacity

11 Information Processing Theory (Shannon, 1952) y Mental processes occur in steps or stages. y Each stage has an input and an output. y Each stage transforms the output of the previous stage in some way. y Each stage has a minimum duration. y Each stage has a limited capacity. y Serial or parallel processing is possible.

12 Birth of Cognitive Psychology 1956 Chomsky (preliminary paper on theory of language) Miller (“The magic number seven, plus or minus two”) Newell and Simon (human problem solving) Also Broadbent (1955), human factors

13 Cognitive Psychology StimulusResponse StimulusResponse Sensation Perception Imagery Retention Recall Problem-solving Thinking Behaviourism (1910s-1950s) Cognitivism (from 1950s) Black box

14 General framework © Model of human information processing (Wickens, 1992)

15 Key concepts The Cognitive Psychology approach is concerned with: y the ways in which information is represented in the mind y and with the processes which act on that information y It does not need not be concerned with the conscious level (the one accessible to introspection) It typically uses an information processing model (expressed as a sequence of processing stages) to predict the time or accuracy of a decision.

16 Information Processing Analysis Example Information Processing Analysis Example

17 Methods (modern) cognitive psychology takes evidence from all 4 areas to try and form an understanding of the human mind Empirical methods Cognitive Neuropsychology Computer modelling Cognitive Psychology Cognitive Neuroscience

18 1. Empirical methods “Cognitive processes and structures are inferred from participants’ behaviour (typically speed and/or accuracy of performance) obtained under well controlled conditions”

19 Methodology y Cognitive psychologists have developed techniques for inferring properties of processing by analyzing relative response times, error rates, or types of judgments. y These methodologies are used to test Hypotheses derived from theories against data. y For example, if there is a discrete module that compares input to lists stored in short-term memory, then it should be possible to describe the sequence of steps or stages through which processing is accomplished

20 Sternberg Experiment Saul Sternberg (1966) proposed a method of studying how people search short-term memory (STM) to determine whether certain information is present. It is one of the 'classic' examples of the information processing paradigm in cognitive psychology. See for a description. Reference: Sternberg, S. (1969) Memory-scanning: Mental processes revealed by reaction-time experiments. American Scientist vol.57,

21 Sternberg Experiment n Sternberg (1966, 1969) developed a procedure that permits a test of two questions about the nature of the search of STM. (1) whether the contents of STM are searched all at once (parallel search) or one item after another (serial search). (2) whether the search stops when the item searched for is found (self- terminating search) or whether all items in STM must be compared to the item searched for (exhaustive search). (In this condition, digits rather than letters)

22 Sternberg's (1969) What do you expect? ßParallel or serial search? ßExhaustive or self- terminating search?

23 Sternberg's (1969) findings What do these data show? Parallel or serial search? (look at positive set, and how RT changes with increasing set size) Exhaustive or self- terminating? (contrast positive and negative sets)

24 Sternberg's (1969) findings 38 msec per digit å Serial search Similar RT (reaction times) for positive and negative answers å Exhaustive search

25 Compare to each item held in memory Sternberg's (1969) model 7 =3 ? Make decision Generate response 38 ms per digit in the memory set 397 ms Yes Perceive stimulus =4 ? =7 ? Input Output

26 Limitations n Indirect information about the internal representations and processes. n Artificial set-up, that rarely corresponds to real-life situations.

27 2. Cognitive Neuropsychology “studies the performance of brain-damaged patients to infer the mechanisms involved -- in normal cognitive functioning”

28 Cognitive Neuropsychology n Example: Semantic vs syntax: Are the processes responsible for generating meaning independent of those responsible for the structure of sentences?   Double dissociation n Based on a Modularity assumption: distinct systems which can suffer damage separately from each other. Production perfomances structure meaning Broca Wernicke Patients

29 Broca’s aphasia Difficulty speaking (telegraphic speech) with poor syntax (“agrammatical aphasia”) but semantically appropriate words. Son … university … smart … boy … good … good …

30 Wernicke’s aphasia Speech is grammatical, but meaningless I called my mother on the television and did not understand the door. It was not too breakfast but they came from far to near. My mother is not too old for me to be young

31 Limitations n It is difficult to carry out group study (when patients are group according to a syndrome, there are variations in performance, in the group). n The strong locality (or modularity of the brain) assumption is not well supported by data. It is not clear that damage to one module “has” only local effect. It is not clear that areas of the brain are fully specialized.

32 3. Computational models (mathematical equations, computer programs, connectionist networks)

33 Box and Arrows Models Single reaction time model (Newell) Limits: n Flowcharts models are never specific enough. y "What happens in the boxes?” y “What do the arrows do?” y “How can the brain be organised like that?” n Implementing a theory as a program is a good method for checking that it contains no hidden assumption or vague terms. n A computer model forces to clearly specify the format of the representations and the nature of the processes.

34 Production systems as computer programs found=0 INPUT digit : IF digit = 3 THEN found=1 IF digit = 4 THEN found=1 IF digit = 7 THEN found=1 : IF found = 0 THEN PRINT "not found" ELSE print "found" n The mind is a seen as a symbol manipulation device. n Note that the speed of the program is not directly compared to the participants’ performance. n Rather, difference in conditions (Task A takes longer than Task B, for both the model and the participants)

35 Connectionist networks Output Values Input Signals (External Stimuli) 1. all input neurons are connected to all output neurons 2. If units A and B and C are simultaneously active, the strength of the connection between them will increase (and B will be triggered faster, next time A is presented)

36 Connectionist breakthrough: NETtalk (Sejnowski & Roseberg, 1986)

37 Problem of the level of description Three levels of description (David Marr) y Computational level : what is computed and why, abstract description of the set of procesing modules required to solve the computation (flowchart, schematic representation). y Algorithmic level : the procedure and representations used. Theorists attempt to discover the way in which processing is actually accomplished within each box (cf. Software program) y Implementational level : the physical instantiation (the brain, the computer) What level matters most?

38 4. Cognitive Neuroscience “[Attempts] to establish where in the brain certain cognitive processes occur, and when these processes occur… with a tendency to combine functional and physiological concepts”

39 Neuroscience Localisation of brain functions in vivo.

40 The idea is to look for converging evidence from different approaches

41 Summary n Cognitive psychologists study how information is represented in the mind, and how those representations are processed n This approach lets us make and test theories about the workings of the mind n These processes don't have to be conscious n Neuropsychological evidence may provide insights into the ways these processes interact

42 Summary (cntd) n There are various ways of modelling information processes; either as a computer program (theory checking) or as a more brain-like neural net n Different types of models may simply describe the same processes at different levels of description


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