I want to know..

• If you could be anywhere right now, where would it be?

The Zimbardo Prison Study

http://www.youtube.com/watch?v=Z0jYx8nwjFQ

Performing an Experiment

• Directly vary a condition you might think affects behavior

• Create two or more groups of subjects, alike in all ways except the condition you are varying

• Record whether varying the condition has any effect on behavior

Advantages and Disadvantages

of Experimental Research• Strengths:

– conclusions about cause-and-effect can be drawn

• Weaknesses: – artificial nature of experiments– ethical and practical issues

Correlation and Causation

• Correlation between two variables DOES NOT (again DOES NOT) mean that one variable CAUSED a change in the other

Correlation between height and weight DOES NOT mean that “tallness” causes heaviness

The Third Variable Problem• Students who watched a lot of television violence, were rated by their

teachers as being more aggressive and prone to violence.

• BUT: One cannot infer causation from these correlations.

• If X and Y are related, that is, if TV Hours are related to aggressive behavior, it does NOT mean that TV Hours CAUSED the aggressive behavior.

• It is equally possible, that aggressive people like to watch aggressive TV. OR, a third variable (such as Social economic status) accounts for the apparent relationship between X and Y

• Solution= experiment: Technique for establishing that casual relationship between variables

Correlation Difficulties

Operationalize Variables

• Translate theoretical concepts into observable information that can be gathered on units of analysis

• How valid are your measures? (internal and external validity)

• How reliable are your measures?

Kinds of Variables

• Independent Variable – something that is changed by the scientist– What is tested– What is manipulated

– It is under control and thus ‘independent’ of what the participant says or does

Kinds of Variables

• Dependent Variable – something that might be affected by the change in the independent variable– What is observed– What is measured– The data collected during the investigation– Its value ‘depends’ on what the participant says

or does

• Controlled Variable

• a variable that is not changed

•Also called constants

•Allow for a “fair test”

Kinds of Variables

Control Group: the group of people who are not treated in a particular way

Experimental Group: the group of people who are treated in a particular way

For Example:

Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the

puzzle.

Identify the variables in this investigation.

What was the independent variable?

• Ages of the students–Different ages were tested by

the scientist

What was the dependent variable?

• The time it took put the puzzle together–The time was observed and

measured by the scientist

What was a controlled variable?

• Same puzzle–All of the participants were

tested with the same puzzle.–It would not have been a fair

test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.

The temperature of water was measured at different depths

of a pond.

• Independent variable – depth of the water

• Dependent variable – temperature• Controlled variable – thermometer

A recent report found that blueberries enhanced the maze running performance of mice. What was the independent variable and dependent variable of this experiment?

Independent variable – BlueberriesDependent variable – Running Performance Controlled variable – Maze

Experiment Types

• Single Blind: Only the subjects have no idea whether they are in the experimental or control group

• Double Blind: The subjects AND the experimenters have no idea whether the subjects are in the control or experimental group– Best type of experiment if properly set up

Experimenter Effects

• Changes in subjects’ behavior caused by the unintended influence of the experimenter’s actions

• Self-Fulfilling Prophecy: A prediction that leads people to act in ways to make the prediction come true

Ethical Issues in Research• Respecting the rights of human research

participants involves:– Informed consent is an explanation of a study and the

responsibilities of experimenter and participant– Deception involving the subjects must be justified– Confidentiality of study information must be maintained– Debriefing refers to explaining the research process to

the subjects at the end of the study

• Animal research must be justified and must minimize discomfort to participants

Do you think the Prison Experiment was ethical?

•an infamous clinical study conducted between 1932 and 1972 in Tuskegee, Alabama 

• Done by the U.S. Public Health Service 

•Aim study the natural progression of untreated syphilis in poor, rural black men

•The men thought they were receiving free health care from the U.S. government.

•Were not told that they had syphilis and went untreated

The Tuskegee syphilis experiment

A doctor draws blood from one of the Tuskegee test subjects– “Testing for Bad Blood”

Animal use in Experimentation

•Animal Welfare Act 1966 (AWA)•Only protects mammals

Psychology in the Media: Separating Fact from Fiction

• Be skeptical• Consider the source of information• Ask yourself, “Was there a control group?”• Look for errors in distinguishing between

correlation and causation (are claims based on correlational results yet passed off as causations?)

• Potential Disadvantages– Sampling bias resulting from self-selection

may be a more troublesome issue in Internet-mediated research

• Web users tend to be younger, brighter, and more affluent than nonusers

– Data are collected under far less controlled conditions than in traditional studies

The Internet and Psychological Research

Design Your Own Experiment

• With a partner, come up with a hypothesis• Choose your variables and identity the

dependent and independent variable and the controlled variable

• Explain what would make your experiment ethical