Anderson was able to derive a power law for relating performance to the
amount of practice.
It is clear that the learning mechanisms that mediate increasing improve-
ments from repeated practice trials must play important roles in the acquisition
of expertise. It may even be useful to consider such mechanisms with an eye to
identifying some limits to their applicability.
First, it is important to distinguish between practice and mere exposure or
experience. It is well known that learning requires feedback in order to be ef-
fective. Hence, in environments with poor or even delayed feedback, learning
may be slow or even nonexistent. Making predictions and forecasts for complex
environments that are dynamically changing can present difficult information-
extraction problems, which may, at least in part, account for the poor perfor-
mance of expert consultants and decision-makers (Camerer & Johnson, 1991).
In addition, merely performing a task does not ensure that subsequent perfor-
mance will be improved. From everyday experience, anyone can cite countless
examples of individuals whose performance never appears to improve in spite
of more than 10 years of daily activity at a task. These observations deserve to
be considered in more detail, but we shall limit ourselves to one issue relevant
to research on expertise: On the basis of the foregoing considerations, one
should be particularly careful about accepting one’s number of years of experi-
ence as an accurate measure of one’s level of expertise.
Second, the learning mechanisms discussed can account only for making the
initial cognitive processes more efficient and ultimately automatic. In real-life
perceptual motor skills, there exist a wide range of motor movements that can
allow realization of a given goal. There is good evidence from sports that the
beginner’s spontaneously adopted baseline strokes in tennis or basic strokes in
swimming are nonoptimal and that it is impossible to improve their efficiency
by iterative refinement. Hence, the first thing a coach will do when beginners
start training is to have them relearn their basic strokes to achieve correct form.
Only then can the basic motor patterns be perfected through further training. It
is thus possible that the final performance levels may reflect differences in the
initial representations used by different subjects.
Third, once we are willing to consider the effects that result from weeks,
months, and years of daily practice, it is likely that we cannot limit the consid-
eration to purely cognitive effects on the central nervous system. Research on
sports performance shows that extensive and intensive training is associated
with a full range of changes related to the blood supply and the efficiency of
muscles (Ericsson, 1990). Such changes will influence the speed of performance.
It is possible that the correlations concerning speed of movements, as measured
by maximum rate of tapping and speed of typewriting (Keele & Hawkins, 1982;
Salthouse, 1984), should be considered not only as reflections of inherited char-
acteristics but also as adaptations of the motor system during years of practice.
Finally, and most important, these types of learning mechanisms focus only
on how performance can be made faster and more efficient; they do not take
into account the acquisition of new cognitive structures, processes that are
prerequisites for the unique ability of experts to plan and reason about problem
situations.
Prospects and Limits of the Empirical Study of Expertise 541