Chapter 22. The Language of Experiments

Learning Objectives

control condition

the “treatment-absent” condition in an experiment (used as a comparison for evaluating the effect of the treatment)

dependent variable

the outcome factor in an experiment that may change in response to manipulations of the independent variable

double-blind procedure

research technique that keeps participants and researchers unaware of which condition each participant has been assigned to in an experiment

experiment

a method of research that manipulates an independent variable to measure its effect on a dependent variable

experimental condition

the “treatment-present” condition in an experiment

independent variable

in an experiment, the experimental factor that is being manipulated, and whose effect is being studied

placebo

in an experiment, false or ineffective treatment administered as if it were the real treatment

placebo effect

in an experiment, any change in behavior due to the participant's expectations rather than to the treatment itself

random assignment

in an experiment, assigning participants to experimental and control conditions by chance, to minimize preexisting differences between the different groups

Psychology’s Subfields

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composite of several illustrations that show experiment procedures with people and animals

Learning Objectives:

Define key terms used in describing psychological experiments.

Distinguish among key terms used in describing psychological experiments.

Review

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The figure is a flow chart with three items linked by arrows. The chart is one directional. At each step, arrows point forward to one box. These steps include the following:
1. Cause or independent variable 2. Effort/outcome or dependent variable 3. Other factor or confounding variable The third step flows back to step 1. A large red X is across the third step to show it is being controlled for or factored out during the experimental process.

Every field of science has its own technical vocabulary, and psychological research is no exception. Here are some essential research terms.

1. Experiments explore cause and effect by manipulating an independent variable, measuring the dependent variable, and controlling all other variables.

Review

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There are two groups, each with the same number of people. The first group is labeled the "treatment group" and the second group is labeled the "control group"

2. An experiment manipulates the independent variable by setting up at least two different conditions: an experimental condition and a comparison, or control condition.

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A group of 10 participants are randomly assigned to two groups. Five are assigned to a treatment group and five are assigned to a control group. Each group is measured after the treatment or control scenario takes place. Then the results from each group are compared

3. Random assignment of subjects to each condition equates the conditions before any treatment begins.

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4. The subjects’ expectations about the treatment may influence their behavior, so the control condition often includes a placebo, or sham treatment (a treatment that actually is not a treatment at all).

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There are three men blindfolded with question marks above their heads. The first man represents a participant who is unaware of being in a control condition that is receiving a placebo. The second man represents a participant who is unaware of being in the experimental condition that is receiving the actual treatment. The third man represents a researcher who is unaware of any participant's status in the experiment.

5. The double-blind procedure ensures that research participants do not know which condition they are in, and this controls for a possible placebo effect. The person evaluating the performance of the participants is also “blind” to the treatment that each participant is receiving, reducing possible experimenter bias.

Practice: Key Terms

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Practice: Key Terms

Roll over each item to see a brief description of that term as it is used in psychological research.

experiment

dependent variable

independent variable

double-blind procedure

control condition

experimental condition

random assignment

placebo

the research strategy that tests behavioral effects of one or more variables (by manipulating an independent variable and measuring the effect on some dependent variable)

the variable being measured in an experiment (to test the outcome of some manipulation of an independent variable)

the variable being manipulated in the experiment (in order to study its effect)

the research procedure in which neither the research participant nor the experimenter knows which condition the participant is in (to control for the placebo effect)

the “treatment-absent” condition in an experiment (used as a comparison for evaluating the effect of the treatment)

the “treatment-present” condition in an experiment

selection of subjects by chance for different conditions in an experiment (to control for other relevant factors)

false or ineffective treatment administered as if it were the real treatment; any change in behavior would be due to the subject’s expectations (the placebo effect) rather than to the treatment

Quiz 1

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Quiz 1

Match the terms with their descriptions by dragging each colored circle to the appropriate gray circle. When all the circles have been placed, select the CHECK ANSWER button.

Perhaps you should go back to review the vocabulary of experiments.

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dependent variable

control condition

experiment

independent variable

experimental condition

placebo

random assignment

double-blind procedure

the variable being manipulated in the experiment

the variable being measured in an experiment

the “treatment-present” condition in an experiment

the “treatment-absent” condition in an experiment

selection of subjects by chance for different conditions in an experiment

the research strategy that tests behavioral effects of one or more variables

the research procedure that controls for the placebo effect

false or ineffective treatment administered as if it were real

Quiz 2

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Quiz 2

Answer the question. Then, select the CHECK ANSWER button.

Try to answer the question again.

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What technique is used to minimize preexisting differences between the treatment group and the control group?

manipulating the independent variable

random assignment

measuring the placebo effect

Conclusion

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The Language of Experiments.