Box 10-1 discusses the Barnum effect in more
detail.
By moving toward quantification, the statistical
approach could eliminate much of the unreliability
in clinical judgment. Objectively derived formulas,
explicit norms, weighted predictors and regression
equations, and carefully stated descriptions and
predictions could combine to replace the fallibilities
of clinical judgment with a standardized procedure
that will minimize errors.
Why, then, do not more clinical psychologists
adopt the statistical approach? There are probably
many reasons some people find statistical approaches
distasteful. Dawes (1979) describes three such reasons.BOX10-1 Focus on Clinical Applications
An Example of a“Barnum Effect”: Purported Characteristics of Adult Children of
Alcoholics (ACOAs)Logue, Sher, and Frensch (1992) examined whether
the apparent widespread acceptance of personality
descriptions of ACOAs was due, at least in part, to a
Barnum effect (following Barnum’s edict:“A circus
should have a little something for everybody”).
Barnum-like statements apply to almost everyone and
therefore appear to be self-descriptive. In reality,
however, they are descriptive of people in general and
lack both a discriminative ability and clinical utility.
Authors of several popular books on ACOAs have
proposed that parental alcoholism produces negative
effects on the family, leading to a host of problems in
children of alcoholics once they become adults. These
include feelings of guilt, shame, insecurity, low self-
esteem, and powerlessness as well as problems coping
with emotions and intimate relationships. Logue et al.
hypothesized that these descriptors have gained pop-
ularity because they not only describe ACOAs but also
tend to be descriptive of people in general.
Two groups of undergraduates (ACOAs and non-
ACOAs) were asked to rate personality profiles as to how
self-descriptive they were. These profiles consisted of six
personality statements (e.g.,“In times of crisis, you need
to take care of others.”). There were two personality
profile types: (a) ACOA personality profile, consisting of
personality statements drawn from the ACOA literature,
and (b) Barnum personality profile, consisting of person-
ality statements drawn from several existing personality
inventories and used in previous Barnum research. These
profileswere matchedon overall levelof social desirability
(assessed through an independent sample). Briefly, results
of the Logue et al. study indicated that ACOA profiles
were rated as highly self-descriptive by both ACOA parti-
cipants and non-ACOA participants. The authors con-
cluded that these popular personality descriptors appear
to have a Barnum-like quality and, therefore, lack validity
as specific descriptors of ACOA individuals.
What are the clinical implications of these and
related findings? Clinicians (and consumers) should bewary of test interpretations and clinical interpretations
that are so general as to fit most anyone. If a single
interpretation (e.g.,“When under sufficient stress, you
get irritable”) fits many people, then it is probably not
going to be helpful in providing a specific characteri-
zation of any one client. Furthermore, it will probably
not be helpful in informing the appropriate treatment
choice or predicting response to treatment.P.T. BarnumArchive Pics/Alamy288 CHAPTER 10