Experimental and Control Groups Experimental Method Experimental and Control Groups

Experiments A formal trial to confirm/disconfirm a hypothesis and to identify cause and effect relationships

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

The Scientific Method

The Experiment An experiment involves a set of controlled conditions that aim to confirm a hypothesis. Hypothesis refers to a statement of cause and effect: “Higher environmental temperatures lead to more aggression.” “Exposure to marijuana increases appetite.”

Variables Any condition that can change and that might affect the outcome of an experiment

Independent Variable Condition(s) altered by the experimenter; experimenter sets their size, amount, or value. These are suspected causes for behavioral differences

Dependent Variable Measures the results of the experiment; Condition is affected by independent variable

Experimental Variables To test a hypothesis, an experimenter defines the variables of the hypothesis: Cause: Independent variable (IV) marijuana: plain cigarette versus cigarette containing 5 mg of THC (the active ingredient in marijuana) Effect: Dependent variable (DV) appetite: grams of ice cream consumed in 1 hour The experimenter “manipulates” the IV and measures the DV to test the hypothesis.

Extraneous Variables Conditions that a researcher wants to prevent from affecting the outcomes of the experiment (e.g., number of hours slept before the experiment)

Groups Experimental Group: The group of subjects that gets the independent variable Control Group: The group of subjects that does NOT get the independent variable Random Assignment: Subject has an equal chance of being in either the experimental or control group

FIGURE 1.8 Elements of a simple psychological experiment to assess the effects of music during study on test scores.

Placebo A fake pill (sugar) or injection (saline) Placebo Effect: Changes in behavior that result from expectations that a drug or other treatment will have some effect; the belief that one has taken an active drug

Experimental Issues Controls are important for determining causality the only difference between the experimental and control groups is the presence or absence of the IV. Placebo effects represent changes in behavior that are related to expectations of a treatment. placebo effects are controlled by a “blind” control group Experimenter bias refers to expectations that influence a participant’s behavior. example: Clever Hans, the horse who could do math can be controlled using double blind procedures

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

The Clinical Method Case Study: In-depth focus of all aspects of a single subject Natural Clinical Tests: Natural events, such as accidents, that provide psychological data

Non-Experimental Research Naturalistic observation refers to systematic recording of behavior in a natural state or habitat. e.g. observing apes in the wild Surveys are instruments designed to sample attitudes or behaviors. e.g., asking students at a rally how they feel about animal rights issues A case study is an in-depth study of a single person. e.g., Freud used the case study method to study anxiety Correlations refer to looking at the relationship between two variables without manipulating them.

Correlation Techniques The correlation technique assesses the degree of association between 2 variables. Correlations vary in direction: Positive association: increases in the value of variable 1 are associated with increases in variable 2 (e.g., smoking and risk of cancer) Negative association: increases in variable 1 are associated with decreases in the variable 2 (e.g., years of education and risk of Alzheimer’s disease) No relation: values of variable 1 are not related to variable 2 (e.g., years of education and height) Correlations also vary in strength of the relationship.

Interpreting Correlations Fig. 1.5

Correlation Take Home Line: Correlation does NOT imply causation!

Stanley Milgram’s Obedience Study 1963 social psychology experiment, subjects thought they were shocking another person to promote “learning” Many subjects delivered high level shocks and were upset when they later learned the true nature of the experiment This study, and other factors, led to much more stringent APA resarch guidlines

APA Ethical Guidelines (humans) informed consent awareness of risks confidentiality deception can be used ONLY if benefits justify it and there is no other way to do the study 48

APA Ethical Guidelines (animals) Researchers must ensure “appropriate consideration of [the animal’s] comfort, health, and humane treatment.” Animals may not be subjected to “pain or stress” when an alternative procedure is available. 49

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. Confidentiality of study information must be maintained. Debriefing refers to explaining the research process to the participants at the end of the study. Deception involving participants must be justified. Animal research must be justified and must minimize discomfort and pain.