Chapter One: What is Psychology?

The Experiment: Hunting for Causes

INTRODUCTION

The experimental method allows researchers to track down the likely causes of behavior.

WHAT'S AHEAD

• Why do psychologists rely so heavily on experiments?
• What, exactly, do control groups control for?
• In a double-blind experiment, who is ‘blind” and what aren’t they suppose to “see”?

KEY CONCEPTS

Overview
Experimental Variables
Experimental and Control Conditions
Experimenter Effects
Conclusion

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Overview

INTRODUCTION

This section is an overview of the basic steps in an experiment.

KEY CONCEPTS EXPLAINED

		An experiment allows the researcher to manipulate the variables in a very controlled situation to determine if changes in one variable produces (causes) changes in the other.
		Because there is manipulation in experiments, great care is taken to ensure ethical and humane treatment.

LINKS on Research Ethics

• wwwlink: The American Psychological Association's Ethics Guidelines.

GLOSSARY

experiment

Experimental Variables

INTRODUCTION

This is the heart of the experimental manipulation to determine cause.

KEY CONCEPTS EXPLAINED

	One variable (independent variable) is manipulated by the researcher to see what its effect will be on the other variable (dependent variable).
	Rules of thumb to decide which is the independent variable and which is the dependent variable;
	The dependent variable depends upon the influence of the independent variable. Look for the one that depends on the other. The "If, then" rule:
	Click on me to learn how to use the rule.

GLOSSARY

		independent variable
		dependent variable

LINKS About experimental methods

• wwwlink: Tutorials written by students on conducting research.
• wwwlink: Everything you ever wanted to know about designing research.

Experimental and Control Condition

INTRODUCTION

To establish cause and effect clearly, this step has to be included to eliminate any preexisting differences that might exist between groups of subjects and insure that everything is held constant except the manipulation of the independent variable.

KEY CONCEPTS EXPLAINED

• Two very similar groups are created by randomly assigning subjects to each group (e.g. flip a coin). This produces two groups that will be roughly equal on any variable, e.g. the same average height, weight, intelligence, income, etc.
  
  
• One group becomes the experimental group because it receives the independent variable. The other group, the control group, is treated exactly the same except it does not receive the independent variable.
  
  
• Logic behind this procedure - When we compare the results from the experimental group with the control group and find there are differences between the two groups on the dependent variable, we are now confident that there weren't any preexisting differences between the two groups.

• Example: If all the subjects with bad driving records were placed in the experimental group and given nicotine, we could not be confident that it was the nicotine that caused the greater number of rear end collisions. However, if we know the groups start out the same, then any difference in the dependent variable has to be due to the effects of the independent variable.

• Placebo: To control for the expectations associated with being a member of the experimental group, a placebo is often given

	Another presentation of the scientific method using the example of bystander apathy.
	location on disk: History and Methods/Science of Psychology/The Scientific Method.

GLOSSARY

		standardize
		norms
		reliability
		validity

LINKS About Psychological Tests

• wwwlink: Debate over the usefulness of standardized tests like the SAT.

Experimenter Effects

INTRODUCTION

Measures need to be taken to make sure that the researcher's personal expectations don't unduly influence the results of the study.

KEY CONCEPTS EXPLAINED

Here are some of the ways in which experimenters keep expectations from influencing the results of the study:

• Single-blind study: subjects don't know whether they are in the experimental or the control group.
  
  
• Double-blind study: Neither the subjects nor the experimenter know who is in the experimental or control group.

GLOSSARY

		experimenter effects
		single-blind study
		double-blind study

LINKS About Surveys

• wwwlink: How various biases can make people think bogus therapies work.
• wwwlink: Facilitated communication exposed in double-blind studies.
• wwwlink: Experimenter bias in hypnosis performance.

Conclusion

INTRODUCTION

If the steps outlined above are done correctly, the experiment allows conclusions to be made about cause and effect relationships between variables. However, there are limitations to the experimental method.

KEY CONCEPTS EXPLAINED

Limitations to the Experimental Method

• The typical subjects in psychological experiments are college students who are not representative of the larger population.
  
  
• Because they know they are in an experiment, subjects may act in ways

Table 1.3 Comparison of the Different Methods Covered in this Chapter.

......................................Interactive Table:
Research Methods in Psychology: Advantages and Disadvantages
Click on Method Name to Jump to the section that describes method in greater detail.

Method		Advantages	Disadvantages
Case Study		Good Source of hypotheses.	Individual may not be representative or typical.
		Provides in-depth information on individuals.	Difficult to know which subjective interpretation is best.
		Unusual cases can shed light on situations or problems that are unethical or impractical to study in other ways.	Allows researcher little or no control of the situation.
Naturalistic Observation		Allows description of behavior as it occurs in the natural environment.	Observations may be biased.
		Often useful in first stages of a research program.	Does not allow firm conclusions on cause and effect.
Laboratory Observation		Allows more control than naturalistic observation.	Allows researcher only limited control of the situation.
		Allows use of sophisticated equipment.	Observation may be biased.
			Does not allow firm conclusions on cause and effect.
			Behavior in the laboratory may differ from behavior in the natural environment.
Tests		Yields information on personality traits, emotional states, aptitudes, abilities.	Difficult to construct tests that are valid and reliable.
Surveys		Provides largest amount of information on large groups of people.	If sample is nonrepresentative or biased, it may be impossible to generalize from the results.
			Responses may be inaccurate or untrue.
Correlational Study		Shows whether two or more variables are related.	Does not permit identification of cause and effect.
		Allows general predictions.
Experiment		Allows researcher to control situation.	Situation is artificial, and results my not generalize well to the real world.
		Permits researcher to identify cause and effect.	Sometimes difficult to avoid experimenter effects.

Next Topic - Evaluating the Findings.......................................... Chapter Contents