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External validity and experimental investigation of individual behaviour

Birnbrauer, J.S. (1981) External validity and experimental investigation of individual behaviour. Analysis and Intervention in Developmental Disabilities, 1 (2). pp. 117-132.

Link to Published Version: http://dx.doi.org/10.1016/0270-4684(81)90026-4
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Abstract

Guidance in conducting internally valid single-subject experiments is now readily available, but there appears to be much doubt and confusion about the issue of external validity, i.e., generality of single-subject research. In the present article, it is argued that rules and conventions for generalizing in group-statistical research are different from those applying to single-subject research. In the absence of such rules, several myths relating to individual analysis have evolved. These are: (1) experiments have external validity; (2) only socially (clinically) significant results are beautiful; (3) classrooms (clinics) are better places to conduct educational (clinical) research than laboratories; (4) the most relevant research is that done with clients similar to mine; (5) knowledge of basic behavioural theory is unnecessary; and (6) baselines are nuisances to be omitted whenever possible. These prevalent misconceptions are discussed and several conclusions drawn. Specifically: (1) studies do not have external validity. Generalization is an active process conducted by consumers, requiring consumers to know the basic literature and theory from which a study stems. To facilitate this process authors should, in their introductions and discussions, place their investigation in a systematic context. (2) Single-subject studies cannot yield predictions about client populations and are not intended to do so. Instead, single-subject studies yield predictions about the effectiveness of an intervention given functional similarity between pretreatment (baseline) conditions and behaviour. (3) For single-subject studies to be used most effectively, investigators should observe, describe, and report baseline conditions in greater detail than presently is the rule.

“To be worthy of the name, an experimenter must be at once theorist and practitioner. While he must completely master the art of establishing experimental facts, which are the materials of science, he must also clearly understand the scientific principles which guide his reasoning through the varied experimental study of natural phenomena. We cannot separate these two things: head and hand. An able hand, without a head to direct it, is a blind tool; the head is powerless without its executive hand” (Bernard, 1957).

In conclusion, (1) studies do not have external validity. Generalization is an active process conducted by consumers, requiring consumers to know the basic literature and theory from which a study stems. To facilitate this process authors should, in their introductions and discussions, place their investigation in a systematic context. (2) Single-subject studies cannot yield predictions about client populations and are not intended to do so. Instead single-subject studies yield predictions about the effectiveness of an intervention given functional similarity between pretreatment (baseline) conditions an behaviour. (3) For single-subject studies to be used most effectively, investigators should observe, describe, and report baseline conditions in greater detail than presently is the rule.

Publication Type: Journal Article
Murdoch Affiliation: School of Psychology
Publisher: Elsevier
Copyright: 1981 Pergamon Press Ltd
URI: http://researchrepository.murdoch.edu.au/id/eprint/20911
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