by Robert L. Woolfolk, Shane M. Murphy, David Gottesfeld, and David Aitken
“The findings of this study suggest that briefly imagining the outcome of athletic
activity immediately prior to performing that activity has greater influence on subsequent performance than does brief mental rehearsal, again prior to performance, of the motor movements that make up the task itself. Although this investigation was the first to employ a design that allowed a controlled comparison between the mental rehearsal of a task immediately prior to performance and the imaginal depiction of its outcome, its results are consistent with those of previous research that found a significant effect for preparational imagery only when an outcome component was included (Gould et al., 1980; Woolfolk et al., in press).The main effect for outcome that emerged in the present investigation reflected a
degradation of performance by negative imagery rather than any enhancement over baseline levels due to the imagination of successful outcome. Our data suggest that picturing a poor result may be more powerful in its ability to damage skilled athletic performance than is positive imagery in its capacity to improve performance.”
http://www.humankinetics.com/acucustom/sitename/Documents/DocumentItem/8804.pdf