Donders Method of Subtraction & Helmholtzs Idea of Unconscious Inference Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/02 /2014: Lecture

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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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 2


Overview of the History of Cognitive Psychology

• Precursors to cognitive psychologyo Aristotle, Plato – epistemology, theory of ideas and their relation

to human action

• Experimental psychology begins in 19th century Germanyo Franciscus Donders (response time analysis, method of subtraction)o Hermann von Helmholtz (perception, unconscious inference)o Hermann Ebbinghaus (experimental study of memory)o Wilhelm Wundt (analytic introspection, analysis of conscious experience)

• Behaviorist hiatus in America: roughly 1920 – 1960o During the behaviorist period (1920-1960), 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


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.o Method of subtraction is an example of a behavioral research method.

Definition of Response Time (RT)

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 ableto measure precisely when the stimulus was presented,and when the subject completed the response.

Psych 355, Miyamoto, Spr '14 5Definition of Simple RT and Choice RT


Method of Subtraction Applied to the ComparisonBetween 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


Diagram of Cognitive Processes During Simple RT

• Simple RT = (Response Completion) – (Stimulus Onset)

In a simple RT task, the subject does not have to decide how to respond.

Time

Diagram Showing Time Course of Choice RT


Diagram of Cognitive Processes During Choice RT

• Choice RT = (Response Completion) – (Stimulus Onset)

In a choice RT task, the subject has to decide which responseis appropriate.

Time

Diagram showing the Decision Stage in the Information Process


• Decision time = the length of time that it takes to decide

which response is appropriate.

Diagram of Cognitive Processes During Choice RT

Question for the Class: How to Measure Decision Time?

Decision Time

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?

Psych 355, Miyamoto, Spr '14 10Diagram comparing simple and choice RT


Method of Subtraction: Compare Simple RT to Choice RT


Choice RT – Simple RT = Duration of Decision Stage (red)

Simple RT

Choice RT

Diagram Showing that the Perceiving Stages are Identical



Simple RT

Choice RT

Diagram Showing that the Responding Stages are Identical

Same Duration



Simple RT

Choice RT

Diagram Showing that the RT Difference Measures the Duration of the Decision Stage

Same Duration



Choice RT – Simple RT = Duration of Decision Stage (red)


Simple RT

Choice RT

What does Donder’s Method Show About Cognitive Psych?

Same Duration


Why is Donder’s Method of SubtractionImportant 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


Subtraction Methods in fMRI Brain Imaging

Activations are regions of significant change from a control condition to a test condition.

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.

Example:

Test Condition: Subject views picture.

Control Condition: Subject fixates a blank screen.

Helmholtz & Unconscious Inference


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)


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


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?


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


Other Important Early Cognitive Research

• Ebbinghaus (1850 – 1909) and the Method of Savingso Important memory researcho We will talk about this later in the course

• Wundt (1832 – 1920)o How sensations combine to form perceptso Analytic introspection

Behaviorist Hiatus


Behaviorist Hiatus – Roughly 1920 - 1960

• John Watsono Influenced by positivist philosophy.

The goal of science is to predict whatever is observable. o Science should eliminate assumptions about whatever is not observable.

(Questionable)o Consciousness is not observable. Eliminate it from psychological theory.

Anti-introspectionist. o 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


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


Wednesday, April 02, 2014: The Lecture Ended Here

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Donders Method of Subtraction & Helmholtzs Idea of Unconscious Inference Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/02 /2014: Lecture