Section 6: The Experiment: Hunting for Causes Psychology Chapter 1

Experiment- allows the researcher to control or manipulate the situation being studied Allows the experimenter to draw conclusions about cause & effect

Must adhere to ethical guidelines In college, a review committee must approve all proposed studies Participants must volunteer & know enough about the study to make an intelligent decision (informed consent) Must protect the participants from physical or mental discomfort or harm Also applies to animals

Experimental variables Independent Variable: A variable that an experimenter manipulates Dependent Variable: A variable than an experimenter predicts will be affected by manipulations of the independent variable

Every experiment has at least one IV & one DV Ideally everything in the experimental situation except the IV is held constant (same for all participants) Ensures that whatever happens is due to the researchers manipulations & nothing else

Experimental & Control conditions Experiments usually require both an experimental & control condition Experimental Condition: A condition in which subjects are exposed to manipulations of the IV Control Condition: A comparison condition in which subjects are not exposed to the same treatment as in the experimental condition

Without a control condition you can’t be sure that the behavior you are interested in would not have occurred anyway without manipulation

Experimental Design Hypothesis: Nicotine in cigarettes impairs driving. All conditions kept the same for both groups except nicotine. Control condition is given placebo (inactive) cigarettes Number of collisions is measured Figure 1.03 from Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall.

Use random assignment to balance individual characteristics A procedure for assigning people to experimental and control groups in which individuals have the same probability as an other of being assigned to either group

May use placebos An inactive substance or fake treatment used as a control in an experiment or given by a practitioner to a patient. Critical when testing new drugs

Experimenter effects Because expectations can influence the results of a study, participants should not know if they are in the experiment or control groups Single blind study

Researchers also bring expectations & may cause unintended changes in subjects’ behavior due to cues inadvertently given by the experimenter Facial expressions, posture, tone of voice, or some other clue

One solution to this problem is to do a double blind study Experiment where neither subjects nor people running the study know which subjects are in the control group and which are in the experimental group until after results are tallied Standard in drug research

Advantages & limitations of experiments Experiments allow conclusions about cause-effect relationships. Participants in experiments are not always representative of larger population. Much psychology research is carried out using college students as participants.

Researcher determines which questions are asked & which behaviors are recorded & the participants try to do what they are told May act different than normal

Dilemma- the more control they exercise over the situation, the more unlike real life it may be Do more field research Descriptive or experimental research conducted in a natural setting outside the laboratory