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Is human probability judgment really so poor? 265
1. Subjects in studies may be unrepresentative of real decision makers
Beach et al. 19 have pointed out that people who typically take part in
experiments designed to assess human judgment are undergraduate
students who may be unrepresentative of real decision makers. Real
decision makers may have acquired skills in probability estimation as a
result of regular experience of carrying out the task and they are also
likely to have expertise relevant to the decision problem. For example,
a sales manager is likely to have expertise on the market for a product
so that any probability judgments will be informed by this expertise.
Undergraduates will usually have no special knowledge which they can
bring to the estimation task and the task of estimating probabilities may
be unfamiliar to them.
2. Laboratory tasks may be untypical of real-world problems
The tasks used in psychological studies have often involved general
knowledge questions, or paper and pencil exercises, similar to some
of those in the questionnaire at the start of this chapter. The way that
subjects approach these tasks may be very different from the way they
tackle judgmental tasks in real-world decision problems. This criticism
is supported by the work of Payne, 20 Payne et al. 21 and Einhorn and
Hogarth 22 who suggest that judgment in laboratory tasks may not be
generalizable to real-world decision making. These researchers found
that even seemingly minor changes in the nature and context of a
judgmental task can have major changes in the way that a problem is
viewed and tackled.
3. Tasks may be misunderstood by subjects
Beach et al. 19 have argued that many of the tasks used in psychological
research are misunderstood by subjects or viewed in a different light than
those expected by the experimenter. For example, in a study designed to
assess the ability of judgmental forecasts to extrapolate an artificial sales
graph with an upward linear trend 23 it was found that subjects tended to
underestimate the extent to which the sales would grow. However, the
experimenters pointed out that subjects may have viewed this not as an
assessment of their ability to extrapolate trends in graphs, but as a test
of their knowledge of the way sales behave in the real world. In many