Improving descriptions of single-subject experiments in research texts written for undergraduates

Many undergraduate research methods texts assume that single-subject experiments are (a) low in generality, (b) merely pilot studies, (c) unsuitable when treatment effects are gradual or irreversible, (d) only useful when multiple-treatment interference is low, and (e) questionable because tests of statistical significance are absent. We critically examine these misconceptions, with the goal of improving the single-subject experiment's description in these texts and increasing its use beyond the area of behavior analysis. We subsequently compare multi-subject and single-subject experimentation in terms of research process and the alignment of psychological research with theory and practice. We conclude that psychological science and practice will be enhanced by methods texts accurately describing single-subject experiments and these texts addressing the problem of "individual-subject validity": the extent causal relations between treatments and outcomes are assessed at the level of the single-subject.