1. Donder’s Method of Subtraction & Helmholtz’s Idea of Unconscious Inference
Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/02/2014: Lecture 01-3
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2. Outline Donder’s Method of Subtraction Method of Subtraction in fMRI
Unconscious Inference
The dominance of behaviorism, 1920 – 1960 (approx.)
The resurgence of cognitive psychology, 1950 – 1970 (approx.)
Psych 355, Miyamoto, Spr '14

3. Overview of the History of Cognitive Psychology
Precursors to cognitive psychology
Aristotle, Plato – epistemology, theory of ideas and their relation to human action
Experimental psychology begins in 19th century Germany
Franciscus Donders (response time analysis, method of subtraction)
Hermann von Helmholtz (perception, unconscious inference)
Hermann Ebbinghaus (experimental study of memory)
Wilhelm Wundt (analytic introspection, analysis of conscious experience)
Behaviorist hiatus in America: roughly 1920 – 1960
During the behaviorist period ( ), cognitive psychology continued to be studied in Europe.
Revival of cognitive psychology in America (1950 – 1970)
1970 – present: Cognitive psychology plays a major role in psychology pretty much everywhere in the world
Donder’s Mental Chronometry
Psych 355, Miyamoto, Spr '14

4. Early Cognitive Psychology: F.C. Donders (1818-1889)
Mental chronometry: Measuring how long a cognitive process takes
Reaction-time (RT) Experiment (a.k.a. response time experiment): Measures interval between stimulus presentation and the response to the stimulus
Method of Subtraction: Used to infer how long a mental process takes when the process is not directly observable.
Method of subtraction is an example of a behavioral research method.
Definition of Response Time (RT)
Psych 355, Miyamoto, Spr '14

5. Terminology: RT (Response Time, Reaction Time)
RT = “response time” (a.k.a. “reaction time”)
RT = (Response Completion) – (Stimulus Onset)
Obviously to measure RT, the experimenter has to be able to measure precisely when the stimulus was presented, and when the subject completed the response.
Definition of Simple RT and Choice RT
Psych 355, Miyamoto, Spr '14

6. Method of Subtraction Applied to the Comparison Between Simple and Choice Reaction Time
Simple RT task: Participant pushes a button quickly after a light appears
Choice RT task: Participant pushes one button if light is on the right side, and a different button if light is on left side
Donder’s goal: To measure how long it takes a person to decide which button to press in the choice RT task.
How long is the decision process?
Diagram Showing Time Course of Simple RT
Psych 355, Miyamoto, Spr '14

7. Diagram of Cognitive Processes During Simple RT
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Time
Simple RT = (Response Completion) – (Stimulus Onset) In a simple RT task, the subject does not have to decide how to respond.
Diagram Showing Time Course of Choice RT
Psych 355, Miyamoto, Spr '14

8. Diagram of Cognitive Processes During Choice RT
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Time
Choice RT = (Response Completion) – (Stimulus Onset) In a choice RT task, the subject has to decide which response is appropriate.
Diagram showing the Decision Stage in the Information Process
Psych 355, Miyamoto, Spr '14

9. Diagram of Cognitive Processes During Choice RT
Decision Time
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Decision time = the length of time that it takes to decide which response is appropriate.
Question for the Class: How to Measure Decision Time?
Psych 355, Miyamoto, Spr '14

10. Question for the Class: How Can We Measure the Duration of the Decision Stage in a Choice RT Task?
Donder’s goal: To measure how long it takes a person to decide which button to press in the choice RT task.
How long is the decision process?
Diagram comparing simple and choice RT
Psych 355, Miyamoto, Spr '14

11. Method of Subtraction: Compare Simple RT to Choice RT
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Choice RT
Method of Subtraction: Choice RT – Simple RT = Duration of Decision Stage (red)
Diagram Showing that the Perceiving Stages are Identical
Psych 355, Miyamoto, Spr '14

12. Method of Subtraction: Compare Simple RT to Choice RT
Same Duration
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Choice RT
Diagram Showing that the Responding Stages are Identical
Psych 355, Miyamoto, Spr '14

13. Method of Subtraction: Compare Simple RT to Choice RT
Same Duration
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Choice RT
Diagram Showing that the RT Difference Measures the Duration of the Decision Stage
Psych 355, Miyamoto, Spr '14

14. Method of Subtraction: Compare Simple RT to Choice RT
Same Duration
See 'D:\p355\RCODE\Donders Method.doc' for the R-code for this figure.
Choice RT
Method of Subtraction: Choice RT – Simple RT = Duration of Decision Stage (red)
What does Donder’s Method Show About Cognitive Psych?
Psych 355, Miyamoto, Spr '14

15. Why is Donder’s Method of Subtraction Important for Cognitive Psychology?
It combines a behavioral study with a simple computational model of a cognitive process.
In Psych 355, we will see many behavioral studies of cognition.
In Psych 355, we will not study the mathematical details of computational models of cognition.
Purely or strictly behavioral studies – no physiological measurements; no brain imaging.
fMRI Method of Subtraction
Psych 355, Miyamoto, Spr '14

16. Subtraction Methods in fMRI Brain Imaging
Activations are regions of significant change from a control condition to a test condition.
Example:
Test Condition: Subject views picture.
Control Condition: Subject fixates a blank screen.
Brain image shows regions of significant activation when comparing Test Condition to Control Condition. (Slice of brain is viewed from above.)
The purpose of this slide is simply to show that subtraction methods are used in modern fMRI studies.
Specific details are not important.
Helmholtz & Unconscious Inference
Psych 355, Miyamoto, Spr '14

17. Early Cognitive Psychology: H. L. F. von Helmholtz (1821 – 1894)
Great mathematician, physicist, psychologist
Contributions to psychology: perception, especially color vision, hearing, optics, unconscious inference
Unconscious inference
Some of our perceptions are the result of unconscious assumptions we make about the environment
We infer much of what we know about the world
Diagram that Illustrates Unconscious Inference (Occlusion)
Psych 355, Miyamoto, Spr '14

18. Unconscious Perceptual Inference
The display in (a) looks like (b) a gray rectangle in front of a light rectangle; but it could be ....
… (c) a gray rectangle and a six-sided figure that are lined up appropriately
or (d) a gray rectangle and a strange-looking figure that are lined up appropriately.
Repeat this Slide without the Rectangles
Psych 355, Miyamoto, Spr '14

19. Unconscious Perceptual Inference
The display in (a) looks like (b) a gray rectangle in front of a light rectangle; but it could be ....
… (c) a gray rectangle and a six-sided figure that are lined up appropriately
or (d) a gray rectangle and a strange-looking figure that are lined up appropriately.
Why is Unconscious Inference Important?
Psych 355, Miyamoto, Spr '14

20. Why Is the Idea of Unconscious Inference Important?
Unconscious inferences contribute in many ways to the formation of our perceptions and beliefs.
Cognitive psychology attempts to reveal the processes by which such inferences are made.
Other Early Cognitive Psychologists – Ebbinghaus & Wundt
Psych 355, Miyamoto, Spr '14

21. Other Important Early Cognitive Research
Ebbinghaus (1850 – 1909) and the Method of Savings
Important memory research
We will talk about this later in the course
Wundt (1832 – 1920)
How sensations combine to form percepts
Analytic introspection
Behaviorist Hiatus
Psych 355, Miyamoto, Spr '14

22. Behaviorist Hiatus – Roughly 1920 - 1960
John Watson
Influenced by positivist philosophy. The goal of science is to predict whatever is observable.
Science should eliminate assumptions about whatever is not observable. (Questionable)
Consciousness is not observable. Eliminate it from psychological theory. Anti-introspectionist.
Opposed to theories that postulated unobserved psychological processes
Clark Hull – Stimulus/Response (S/R) learning model.
Edwin Guthrie
B. F. Skinner – Reinforcement theory
Behaviorism was an American approach to psychology – not so influential in Europe and elsewhere.
Cognitive Psychology During the Behaviorist Period
Psych 355, Miyamoto, Spr '14

23. Cognitive Psychology During the Behaviorist Period
William James (1842 – 1910; cognitive psychology)
Jean Piaget – genetic epistemology
Lev Vygotsky – cognitive development and education
Sir Frederick Bartlett (constructive memory processes)
Gestalt psychology – Kurt Lewin, Wolfgang Kohler
The beginnings of the computer revolution. Alan Turing, Norbert Wiener, John von Neumann
Behaviorism Loses Its Grip on Psychology
Psych 355, Miyamoto, Spr '14

24. Wednesday, April 02, 2014: The Lecture Ended Here
Psych 355, Miyamoto, Spr '14