■ Studies with judgment outcomes that wereless
valid had greater effect sizes. In contrast, the
studies that included judgment criteria with the
highest validity on average showed no rela-
tionship between clinical experience and
accuracy of judgment!
■ Finally, studies published in higher-quality
journals tended to higher associations between
experience and judgment.
So, what do we make of these findings? As noted
by Spengler et al. (2009), even though an overall
significant effect was found,“Training and experience
may only improve things modestly for the profes-
sional.”(p. 383) As noted above, the effect size was
quite small by any standards (e.g., typically an effect
size of .20–.30 is considered“small”). So, overall,
these results should be humbling to those that place
great value on clinical experience when making judg-
ments. Second, the finding that larger effects were
reported in studies with less valid criterion measures
of judgment is also disconcerting. Could it be that the
overall effect is primarily due to these lower-quality
studies? Finally, it is important to note that these stud-
ies did not compare clinical and statistical prediction.
Instead, they only addressed whether clinical experi-
ence improved clinical prediction. The general con-
clusion that statistical prediction outperforms clinical
prediction overall remains intact.
As for the virtue of receiving specific types of
professional training, there is not much evidence
to suggest that one profession is superior to an-
other in making accurate diagnostic judgments.
For example, even in differentiating psychological
symptoms that are masking medical disorders from
those without underlying medical disorders, medi-
cal and non-medical practitioners did not differ
in their accuracy (Garb, 2000; Grove et al., 2000;
Sanchez & Kahn, 1991).
All of this research is somewhat sobering for
the field of clinical psychology. However, it is our
professional responsibility to be aware of the limits
of our predictive ability and not to promote the
“myth of experience.”One thing is sure. Clinicians
will continue to make decisions because they have
no choice. The important point is to ensure that
clinical psychologists are as well prepared as they
can be, as well as to train clinical psychologists to
use the best available measures and techniques for a
given prediction situation.Conclusions
Given the current state of affairs, the following con-
clusions regarding the relative strengths of clinical
and actuarial methods seem warranted.
The clinical approach is especially valuable when:- Information is needed about areas or events for which
no adequate tests are available. In this case, the
research fails to offer any evidence that the
data-gathering function of the clinician can be
replaced by a machine. - Rare, unusual events of a highly individualized
nature are to be predicted or judged. Regression
equations or other formulas cannot be devel-
oped to handle such events, and clinical judg-
ment is the only recourse. - The clinical judgments involve instances for which no
statistical equations have been developed. The vast
majority of instances, in effect, fall into this
category (Garb, 2000). The day-to-day deci-
sions of the clinician are such that the avail-
ability of a useful equation would itself be a
rare and unusual event. - The role of unforeseen circumstances could negate the
efficiency of a formula. For example, a formula
might very easily outstrip the performance of a
clinician in predicting suitability for hospital
discharge. In the role of data gatherer, how-
ever, the clinician might unearth important
data from a patient that would negate an oth-
erwise perfectly logical statistical prediction.
The statistical approach is especially valuable
when: - The outcome to be predicted is objective and specific.
For example, the statistical approach will be
especially effective in predicting grades, suc-
cessful discharge, vocational success, and similar
objective outcomes.
296 CHAPTER 10