Methods in Cognitive Psychologypeople.uncw.edu/tothj/PSY410/PSY410-01b-Methods-bw.pdfMethods in...
Transcript of Methods in Cognitive Psychologypeople.uncw.edu/tothj/PSY410/PSY410-01b-Methods-bw.pdfMethods in...
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Methods in Cognitive Psychology
Experimental Methods in Cog Psych.
• The Role of Baseline Conditions.• Accuracy & Signal Detection Theory.
• Reaction Time (RT) & Donder's Subtraction Method.
What is cognition? How can we explain how cognition works?
• Mental representations & mental processes.
Research Methods (see Galotti, pp. 12-15).• Observation, Introspection, Experiments, Brain Studies.
Excel Tutorial & Lab 1
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Mental Representations A representation is a physical state (e.g., marks on a
page, magnetic fields in a computer, neural connections in the brain) that stands for something.
Representations have two characteristics: A format(how it's realized) and a content (what it stands for).
A lot of work in cognitive psychology is devoted to understanding the nature of mental and/or neural representations.
• Memory traces.• Words in our "mental lexicon" (mind's dictionary).
Examples of mental representations include…
• Concepts.• Images.
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Mental Processes Representations don’t do anything unless they are
processed (or interpreted).
Much work in cog psych is directed at discovering mental processes & understanding how they work.
A process is the transformation of an input (e.g., two numbers) into an output (e.g., a sum).
• Visual search.• Short-term memory.
Examples of mental processes include…
• Selective Attention.• Executive functions (planning, inhibition, etc.).
Most interesting cognitive activities (e.g., memory, thinking) reflect the operation of multiple processes.
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How many guys did you go out with in college?
Oh, I never dated much in college. Speech
Recognition
Interpretation
Memory Retrieval
Decision about how to answer
Speechproduction
events like this occur very quickly; how can we "break them down" to understand the representations and processes involved?
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the time it takes to respond to something; usually the time between some stimulus (S) and some response (R).
sometimes referred to as "mental chronometry".
many cognitive processes occur very quickly and thus are measured in milliseconds (ms); 1 ms = 1/1000th of a second.
Reaction Time (RT)
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Is Visual Search Serial or Parallel?
Do we search the world serially, examining one item at a time?
Or do we search in parallel, simultaneously examining all the objects in our visual field?
Reaction Time (RT)
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Reaction Time (RT)
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Processing stages and Donder's (1868) subtraction method
Detection
Categorization
Response Selection
Responding
Reaction Time (RT)
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Simple RT Task*
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* RT = Detection + Responding.
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Complex (Choice) RT Task*
* RT = Detection + Categorization +Response Selection + Responding.
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circle = key 1square = key 2
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Subtraction MethodDonders (1868)
- Simple RT = 350 msChoice RT = 500 ms
Detection
Categorization
Response Selection
Responding
150 ms= Categorization and Response Selection
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Methods in Cognitive Psychology
Experimental Methods in Cog Psych.
• The Role of Baseline Conditions.• Accuracy & Signal Detection Theory.
Reaction Time (RT) & Donder's Subtraction Method.
What is cognition? How can we explain how cognition works? Mental representations & mental processes.
Research Methods (see Galotti, pp. 19-23). Observation, Introspection, Experiments, Brain Studies.
Excel Tutorial & Lab 1
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Amount of sleepMemory
performance
1 hour 65%
8 hours 68%Baseline condition
The Role of Baseline Conditions
Take-Home Message: You can't learn much from an expt without an appropriate baseline or comparison condition.
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Studied words (% "yes")
Subject A 85%
The Role of Baseline ConditionsImagine you want to test people's memory. To do so, you show them a list of 50 words and then, after a delay, show them those words again and ask if they remember seeing any on the previous list (saying "yes" if they did, "no" if they didn't).
Subject B 65%
Unstudied words (% "yes")
75%15%
Hits False Alarms
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HIT FALSE ALARM
MISS CORRECT REJECTION
Stimulus Present?Yes No
"Yes"
"No"
Subject's Response
Accuracy in Detecting Signals
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Signal Detection Theory
HIT FALSE ALARM
Stimulus Present?Yes No
"Yes"
Person A: 90% 50%Person B: 60% 20%
Does the "star field" to the left contain a set of 10 equidistant dots arranged in straight line that slants downward from left to right?
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signal strength
prob
abili
ty
Signal Detection Theory Assumes that detection reflects 2 processes.
1. Sensitivity - Person's true ability to discriminate targets (signal) from non-targets (noise).
2. Response Criterion (Bias) - Person's tendency to claim they have detected a signal ("yes").
"Yes""No"
Noise trials
Signal trials
Rsp. Crit.
Sensitivity
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signal strength
prob
abili
ty
Signal Detection Theory
"Yes""No"
Noise trials
Signal trials
Rsp. Crit.
Sensitivity
HitsMisses False Alarms
Correct Rejections
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Signal Detection Theory Applies to....
• Memory • Radar Operators• Medical Decisions • Baseball
signal strength
prob
abili
ty
"Yes""No"
Noise trials
Signal trials
Rsp. Crit.
Sensitivity
etc. etc. etc...
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HIT FALSE ALARM
Stimulus Present?Yes No
"Yes"
Signal Detection Theory
Situation A: 90% 70%
Situation B: 45% 5%
Situation A:Hit = +$10FA = -$1
Situation B:Hit = +$1FA = -$10
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• Type I & Type II errors have many real-world consequences...Type I & Type II Errors
In the hospital.
False Alarm
Miss
Hit
Correct Reject.
+-
+
-
In court decisions... False Alarm
Miss
Hit
Correct Reject.
+-
+
-
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Methods in Cognitive Psychology
Experimental Methods in Cog Psych.
The Role of Baseline Conditions. Accuracy & Signal Detection Theory.
Reaction Time (RT) & Donder's Subtraction Method.
What is cognition? How can we explain how cognition works? Mental representations & mental processes.
Research Methods (see Galotti, pp. 19-23). Observation, Introspection, Experiments, Brain Studies.
Lab 2: Signal Detection.