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Research Methods in Psychology: Experimental Research

Research Methods in Psychology
Experimental Research

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Notes

table of contents
  1. Acknowledgements
  2. About this Book
  3. About the Authors of the Current Edition
  4. Preface
  5. The Science of Psychology
    1. Methods of Knowing
    2. Understanding Science
    3. Goals of Science
    4. Science and Common Sense
    5. Experimental and Clinical Psychologists
    6. Key Takeaways and Exercises
  6. Overview of the Scientific Method
    1. A Model of Scientific Research in Psychology
    2. Finding a Research Topic
    3. Generating Good Research Questions
    4. Developing a Hypothesis
    5. Designing a Research Study
    6. Analyzing the Data
    7. Drawing Conclusions and Reporting the Results
    8. Key Takeaways and Exercise
  7. Research Ethics
    1. Moral Foundations of Ethical Research
    2. From Moral Principles to Ethics Codes
    3. Putting Ethics Into Practice
    4. Key Takeaways and Exercises
  8. Psychological Measurement
    1. Understanding Psychological Measurement
    2. Reliability and Validity of Measurement
    3. Practical Strategies for Psychological Measurement
    4. Key Takeaways and Exercises
  9. Experimental Research
    1. Experiment Basics
    2. Experimental Design
    3. Experimentation and Validity
    4. Practical Considerations
    5. Key Takeaways and Exercises
  10. Non-Experimental Research
    1. Overview of Non-Experimental Research
    2. Correlational Research
    3. Complex Correlation
    4. Qualitative Research
    5. Observational Research
    6. Key Takeaways and Exercises
  11. Survey Research
    1. Overview of Survey Research
    2. Constructing Surveys
    3. Conducting Surveys
    4. Key Takeaways and Exercises
  12. Quasi-Experimental Research
    1. One-Group Designs
    2. Non-Equivalent Groups Designs
    3. Key Takeaways and Exercises
  13. Factorial Designs
    1. Setting Up a Factorial Experiment
    2. Interpreting the Results of a Factorial Experiment
    3. Key Takeaways and Exercises
  14. Single-Subject Research
    1. Overview of Single-Subject Research
    2. Single-Subject Research Designs
    3. The Single-Subject Versus Group “Debate”
    4. Key Takeaways and Exercises
  15. Presenting Your Research
    1. American Psychological Association (APA) Style
    2. Writing a Research Report in American Psychological Association (APA) Style
    3. Other Presentation Formats
    4. Key Takeaways and Exercises
  16. Descriptive Statistics
    1. Describing Single Variables
    2. Describing Statistical Relationships
    3. Expressing Your Results
    4. Conducting Your Analyses
    5. Key Takeaways and Exercises
  17. Inferential Statistics
    1. Understanding Null Hypothesis Testing
    2. Some Basic Null Hypothesis Tests
    3. Additional Considerations
    4. From the “Replicability Crisis” to Open Science Practices
    5. Key Takeaways and Exercises
  18. Glossary
  19. References

V

Experimental Research

In the late 1960s social psychologists John Darley and Bibb Latané proposed a counter-intuitive hypothesis. The more witnesses there are to an accident or a crime, the less likely any of them is to help the victim (Darley & Latané, 1968)[1].

They also suggested the theory that this phenomenon occurs because each witness feels less responsible for helping—a process referred to as the “diffusion of responsibility.” Darley and Latané noted that their ideas were consistent with many real-world cases. For example, a New York woman named Catherine “Kitty” Genovese was assaulted and murdered while several witnesses evidently failed to help. But Darley and Latané also understood that such isolated cases did not provide convincing evidence for their hypothesized “bystander effect.” There was no way to know, for example, whether any of the witnesses to Kitty Genovese’s murder would have helped had there been fewer of them.

So to test their hypothesis, Darley and Latané created a simulated emergency situation in a laboratory. Each of their university student participants was isolated in a small room and told that they would be having a discussion about university life with other students via an intercom system. Early in the discussion, however, one of the students began having what seemed to be an epileptic seizure. Over the intercom came the following: “I could really-er-use some help so if somebody would-er-give me a little h-help-uh-er-er-er-er-er c-could somebody-er-er-help-er-uh-uh-uh (choking sounds)…I’m gonna die-er-er-I’m…gonna die-er-help-er-er-seizure-er- [chokes, then quiet]” (Darley & Latané, 1968, p. 379).

In actuality, there were no other students. These comments had been prerecorded and were played back to create the appearance of a real emergency. The key to the study was that some participants were told that the discussion involved only one other student (the victim), others were told that it involved two other students, and still others were told that it included five other students. Because this was the only difference between these three groups of participants, any difference in their tendency to help the victim would have to have been caused by it. And sure enough, the likelihood that the participant left the room to seek help for the “victim” decreased from 85% to 62% to 31% as the number of “witnesses” increased.

The Parable of the 38 Witnesses

The story of Kitty Genovese has been told and retold in numerous psychology textbooks. The standard version is that there were 38 witnesses to the crime, that all of them watched (or listened) for an extended period of time, and that none of them did anything to help. However, recent scholarship suggests that the standard story is inaccurate in many ways (Manning, Levine, & Collins, 2007)[2]. For example, only six eyewitnesses testified at the trial, none of them was aware that they were witnessing a lethal assault, and there have been several reports of witnesses calling the police or even coming to the aid of Kitty Genovese. Although the standard story inspired a long line of research on the bystander effect and the diffusion of responsibility, it may also have directed researchers’ and students’ attention away from other equally interesting and important issues in the psychology of helping—including the conditions in which people do in fact respond collectively to emergency situations.

The research that Darley and Latané conducted was a particular kind of study called an experiment. Experiments are used to determine not only whether there is a meaningful relationship between two variables but also whether the relationship is a causal one that is supported by statistical analysis. For this reason, experiments are one of the most common and useful tools in the psychological researcher’s toolbox. In this chapter, we look at experiments in detail. We will first consider what sets experiments apart from other kinds of studies and why they support causal conclusions while other kinds of studies do not. We then look at two basic ways of designing an experiment—between-subjects designs and within-subjects designs—and discuss their pros and cons. Finally, we consider several important practical issues that arise when conducting experiments.

  1. Darley, J. M., & Latané, B. (1968). Bystander intervention in emergencies: Diffusion of responsibility. Journal of Personality and Social Psychology, 4, 377–383. ↵
  2. Manning, R., Levine, M., & Collins, A. (2007). The Kitty Genovese murder and the social psychology of helping: The parable of the 38 witnesses. American Psychologist, 62, 555–562. ↵

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Copyright © 2019

                                by Rajiv S. Jhangiani, I-Chant A. Chiang, Carrie Cuttler, & Dana C. Leighton

            Research Methods in Psychology by Rajiv S. Jhangiani, I-Chant A. Chiang, Carrie Cuttler, & Dana C. Leighton is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.
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