Less is More: Why Psychologists Can Learn More About Functional Relations by Studying Fewer People

Psychology has been embroiled in a professional crisis as of late. The research methods commonly used by psychologists, especially the statistical analyses used to analyze experimental data, are under scrutiny. The lack of reproducible research findings in psychology and the paucity of published studies attempting to replicate psychology studies have been widely reported. Although it is encouraging that people are aware of problems evident in mainstream psychology research and taking actions to correct them, one problem has received little or no attention: the reliance on between-subjects research designs. The reliance on group comparisons is arguably the most fundamental problem at hand because such designs are what often necessitate the kinds of statistical analyses that have led to psychology’s professional crisis. Typically, functional relations are inferred rather than demonstrated. In contrast, single-case experiments yield data that can be interpreted using non-inferential statistics and visual analysis of graphed data, a strategy characteristic of other natural sciences. Single-case experimental designs are advantageous because they more readily permit the intensive investigation of each subject and they achieve replication, and thus demonstrate functional relations, within an experiment rather than across experiments. As a result, data from just a few subjects tells a story.