performance of the MP group exceeds that of the control group, a positive effect of
mental practice is reported.
Based on this experimental paradigm, a number of general conclusions about mental
practice have emerged. First, relative to not practising at all, MP appears to improve
skilled performance. However, MP is less effective than is physical practice. More
precisely, a meta-analytic review by Driskell et al. (1994) showed that physical practice
(PP) treatment conditions produced greater statistical effect sizes than was evident in
mental rehearsal conditions (recall from Chapter 2 that “meta-analysis” is a statistical
technique which combines the results of a large number of studies in order to determine
the overall size of a statistical effect). Statistically, the relative effect sizes of physical
practice and mental practice were estimated by these researchers as 0.382 and 0.261 (both
Fisher’s Z), respectively. These figures can be interpreted with reference to Cohen’s
(1992) suggestion that values of 0.20, 0.50 and 0.80 represent effect sizes that are small,
medium and large, respectively. The second general finding from the research literature is
that MP, when combined and alternated with physical practice, seems to produce superior
skill-learning to that resulting from either mental or physical practice conducted alone.
Third, research suggests that mental practice improves the performance of cognitive skills
(i.e., those that involve sequential processing activities; e.g., mirror drawing tasks) more
than it does for motor skills (e.g., as balancing on a stabilometer). Next, there seems to be
an interaction between the level of expertise of the performer and the type of task which
yields the best improvement from mental rehearsal (Driskell et al., 1994). Specifically,
expert athletes tend to benefit more from MP than do novices, regardless of the type of
skill being practised (either cognitive or physical). Fifth, the positive effects of MP on
task performance tend to decline sharply over time. Indeed, according to Driskell et al.
(1994), the beneficial effects of visualisation are reduced to half of their original value
after approximately two weeks of time has elapsed. A practical implication of this finding
is that in order to gain optimal benefits from mental practice, “refresher” training should
be implemented after this critical two-week period. Finally, there is evidence that
imagery ability mediates the relationship between MP and motor skill performance. More
precisely, athletes who display special skills in generating and controlling vivid images
tend to benefit more from visualisation than do counterparts who lack such abilities. In
summary, there is now considerable evidence (much of it experimental) to support the
efficacy of mental practice as a technique for improving the performance of a variety of
sport skills. These skills include not only “closed” actions (i.e., ones which are self-paced
and performed in a relatively static environment) such as golf putting or place-kicking in
rugby but also “open” or reactive skills. For example, the rugby tackle (McKenzie and
Howe, 1991) and the counter-attacking forehand in table-tennis (Lejeune, Decker and
Sanchez, 1994) have shown improvements under mental rehearsal training.
Critical evaluation of research on mental practiceAt first glance, the preceding evidence on the efficacy of mental practice conveys the
impression of a vibrant and well-established research field in cognitive sport psychology.
But closer inspection reveals a less satisfactory picture. Specifically, as I mentioned in
the previous section, MP research has encountered many conceptual and methodological
criticisms over its century-long history (see Moran, 1996; Murphy and Martin, 2002). Of
Sport and exercise psychology: A critical introduction 132