Deutsch: Einzelfallstudie / Español: Experimento de sujeto único / Português: Experimento de sujeito único / Français: Expérience sur sujet unique / Italiano: Esperimento su singolo soggetto

Single Subject Experiment, in the context of psychology, refers to a research design that focuses on closely observing and measuring the behavior of a single participant over time to determine the effects of a specific intervention or treatment. This approach contrasts with group studies, which compare outcomes across multiple participants. Single subject experiments are particularly useful in applied psychology fields, such as clinical psychology, educational psychology, and behavioral therapy, where individual variability and the effectiveness of personalized interventions are of interest.


Single subject experiments often employ a baseline measurement (A), followed by an intervention phase (B), and sometimes a return to baseline or a new intervention phase (A-B-A-B design). The key feature of this design is the repeated measurement of behavior over time, allowing for the observation of changes directly attributable to the intervention. This method is valuable for demonstrating cause-and-effect relationships within an individual, even without a large sample size.

Application Areas

  • Clinical Psychology: To evaluate the effectiveness of therapeutic interventions for disorders such as anxiety, depression, or specific phobias on an individual basis.
  • Educational Psychology: To assess the impact of educational interventions, teaching methods, or behavior management strategies on a single student.
  • Behavioral Therapy: To monitor and modify problematic behaviors in individuals with behavioral issues, developmental disorders, or special needs, using tailored interventions.

Well-Known Examples

A classic example of a single subject experiment is the application of a behavioral intervention to reduce disruptive behaviors in a classroom setting. By implementing a specific strategy (e.g., a reward system) for one student and measuring the frequency of disruptive behaviors before, during, and after the intervention, researchers can ascertain the effectiveness of the intervention for that individual.

Treatment and Risks

While single subject experiments can provide detailed insights into the effectiveness of interventions for individuals, one limitation is the challenge of generalizing findings to a broader population. However, when multiple single subject studies yield similar results across different individuals, these findings can contribute to the evidence base for specific treatments or interventions.

Similar Terms or Synonyms

  • N=1 study
  • Case study research (though it may not always involve an experimental intervention)


Single Subject Experiment designs in psychology are a powerful method for investigating the effects of interventions on individual behavior. By focusing on detailed observation and measurement of a single participant, these experiments can provide valuable insights into the effectiveness of specific therapeutic, educational, or behavioral interventions, tailored to individual needs and contexts.


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