Mental rehearsal has been shown to be effective in improving performance on psychomotor tasks. This study examined the effects of covert practice on accuracy in two different throwing tasks, using thirty undergraduate college students. Results indicate that mental rehearsal has a positive effect on performance, but that this effect is variable according to the task and amount of time spent rehearsing.
Mental rehearsal (mental practice) is defined as, "the cognitive rehearsal of a task in the absence of overt physical movement" (Driskell, Cooper, & Moran, 1994). Several studies have shown that mental rehearsal can improve psychomotor and sport performance. Doheny (1993) demonstrated in nursing students that mental practice can improve the technique of administering an intramuscular injection. Another study concluded that mental rehearsal is better than no practice at improving accuracy on a simple hand-eye coordination task (Smith & Harrison, 1962). Finally, table tennis performance was improved more by a combination of physical and mental practice than by physical practice alone (Lejeune, Decker, & Sanchez, 1994).
Both physical and mental rehearsal clearly can improve performance of some motor tasks. Comparatively, though, physical practice was shown to be more effective than mental practice alone in a meta-analysis done by Driskell et al., (1994). Therefore, we decided that another experiment on the relative effects of mental versus physical rehearsal was unnecessary. Instead, we chose to examine how much mental rehearsal would be necessary to produce an improvement in performance of throwing accuracy tasks.
Furthermore, this study examined the specificity of mental practice. Does mental practice of a particular motor task improve performance on only that task or does the effect generalize itself to other motor tasks? To examine this, the subjects performed two throwing tasks before and after their mental rehearsal or waiting period. This provided a type of control for examining the generalizability of mental rehearsal.
Thirty undergraduate students served as subjects, 12 males and 18 females, divided into 6 groups randomly. Groups 1 and 2 mentally rehearsed ball throwing and ring tossing, respectively, for 30 seconds. Groups 3 and 4 mentally rehearsed the same respective tasks as groups 1 and 2, but for 60 seconds. Group 5 was a control group that was asked to answer a bogus survey, consisting of three questions pertaining to gambling, timed for 10 seconds each. Group 6 was a second control group who answered another bogus survey on gambling, consisting of six questions for a total of 60 seconds. These time periods were chosen for the following reason: Driskell et al. (1994) argued that increasing the amount of mental practice that subjects perform can improve performance on motor tasks, but that too much practice will nullify the effect.
The ball toss used ten tennis balls and a rectangular shaped wastepaper basket measuring 18" x 9" x 18" (LxWxH). The ring toss used 10 rings cut from a 4 inch PVC pipe, each ring measuring one inch in thickness. A 3/8" dowel measuring 13" tall was affixed to a platform that was used as the ring target. A Macintosh computer with Superlab software was used during the rehearsal and waiting periods.
Subjects stood 88 inches away from the basket and threw the balls overhand with their non-dominant hand and 66 inches from the ring target and tossed the rings again with their non-dominant hand, frisbee style. After performing both of the throwing tasks once, the subjects were instructed to go into an isolation room and to either think about one of the throwing tasks or to complete the survey. The instructions were presented to them on the computer, which also served as a timer to tell them when they had finished. After the rehearsal or waiting period was over the subjects completed both throwing tasks again, with the mental rehearsal groups performing first whichever task they rehearsed.
The results of this experiment are summarized in Figures 1-4. Addressing the question of the specificity of mental task rehearsal, ring rehearsal did not seem to improve accuracy on the ring toss. Instead, it improved performance on the ball throwing task. Also, ball throwing improved as much in the absence of ring rehearsal as with rehearsal (see Fig. 1). Furthermore, mental ball throwing rehearsal improved ring tossing more than ball throwing. In fact, it had a detrimental effect on ball throwing accuracy. The greatest improvement in ball throwing accuracy was seen in the no rehearsal groups (see Fig. 2).
The other major question of this experiment was how the amount of time spent mentally rehearsing affected the amount of improvement on the tasks. In ring tossing, both of the no rehearsal groups (30 and 60 seconds) improved the same amount, while the 30 second rehearsal group had the greatest improvement and the 60 second group had the least (see Fig. 3). In ball throwing, both of the rehearsal groups improved the same amount, with the 30 second no rehearsal group improving more than either rehearsal group and the 60 second no rehearsal group improving the most of all (see Fig. 4).
It was expected that all groups would improve their performance on these throwing tasks since all the tasks were relatively new to the subjects. So, some practice effect was inevitable. Furthermore, mental rehearsal of throwing tasks should have improved accuracy on the specific task rehearsed more than from the practice effect alone. But this was not the case. Instead, the no rehearsal groups consistently improved more than the rehearsal groups. This could be due to two factors. First, the survey that was given to the no rehearsal group to occupy them while they waited asked questions about gambling. It is possible that the survey could have mentally excited the subjects to the point that they had an incentive to improve, based on stimulating their desire to win at gambling. Second, the mental rehearsal groups received little instruction in mental practice, and it is likely that many of them did not know how to mentally practice or were disinterested in doing it. It would have been helpful to administer a survey of mental imagery capability to the subjects and to correlate this with their improvements after rehearsal. Any further research on this specific topic should include an index of this type.
On the issue of the amount of practice required to produce an effect, previous research suggests that increasing the rehearsal time can improve the effects observed, but that increasing it too much can eliminate the effect. It is likely that subjects will become distracted or disinterested if the rehearsal time is too long. Possibly, 60 seconds is near the upper limit of the subjects' attention span for these specific tasks, which could explain why more improvement was seen in the groups rehearsing for 30 seconds than 60.
Finally, the largest finding of this study was that improvements in specific tasks were seen when subjects mentally rehearsed the other task. There are two possible explanations for this. First, the instructions given to the subjects may not have been followed correctly. Possibly, the subjects thought about both of the tasks together rather than the one task they were told to focus on. In fact, one subject actually did report having misread the instructions and mentally rehearsed both of the tasks. Looking at this subject's individual results, improvement was seen in both of the throwing tasks equally. In future experiments, instructions should be made more explicit to eliminate the subjects' personal preferences. Second, the effects of mental rehearsal may be more general than previously believed. Possibly, mental rehearsal of any throwing task will improve performance on all related throwing tasks. Although we tried to pick two tasks which would not exhibit this cross-effect, the two throwing tasks may be enough related that rehearsing one affects the other.
Doheny MO. (1993). Effects of Mental Practice on Performance of a Psychomotor Skill. Journal of Mental Imagery, 17(3&4), 111-18.
Driskell JE, Cooper C, Moran A. (1994). Does Mental Practice Enhance Performance? Journal of Applied Psychology, 79(4), 481-92.
Lejeune M, Decker C, Sanchez X. (1994). Mental Rehearsal in Table Tennis Performance. Perceptual and Motor Skills, 79, 627-41.
Smith LE, Harrison JS. (1962). Comparison of the Effects of Visual, Motor, Mental, and Guided Practice upon Speed and Accuracy of Performing a Simple Eye-Hand Coordination Task. The Research Quarterly, 33(2), 299-307.
SuperLab version 1.68 (1992). Cedrus Corp.
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