Enhancing Human Performance Issues, Theories, and Techniques, Background Papers (Complete Set) (1988) / Chapter Skim
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PART III. Improving Motor Performance
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Becker Michigan State Univers ity Running hesd: MENTAL PRACTICE Send correspondence to Deborah L .
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learning effects by means of effect sizes for pretest-to-posttest differences, (2) mental practice effects compared to no practice, physical practice, and mental and physical practice, and (3)
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The specific research question addressed in these studies has been whether a given amount of mental practice prior to performing a motor skill will enhance one's subsequent motor performance. Unfortunately, definitive answers to this question have not been readily forthcoming.
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of sub jects who had previous mental practice to a control group that had not received mental ins tractions . In the mental practice group the time intervening between pre and posttest was usually occupied in sitting or standing and rehearsing the skill in imagination for a set amount of time.
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By contrast, the present review included only single or multiple group studies having pre and posttest scores. The use of pre-post designs permitted a determination of a change-score effect size for each group examined in this set of mental practice studies.
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physical practice is better than mental practice; and (b) mental practice combined and alternated with physical practice is more effective than either p by s i ca 1 p ra c t i ce or me nt a 1 p ra ct i c e a 1 o n e .
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were helpful. In the above reviews, however, the conclusions about mental practice effects may have been distorted for one or more of the following reasons: (a)
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, is next introduced: this measure serves as an index of the effectiveness of mental practice training in our review. A Overview of hypotheses tested by statistical method designed specifically for analyzing effect-size data (e.g., Hedges & Olkin, 1985)
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Ment al Pra ct ice 9 (e.g., Birge' 1932; Fisher, 1932) , used to summarize research results Glass ( 1976)
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Problem Formulation At this first stage of the review, the researcher must outline the research questions f or the review and the kinds of evidence that should be sought in order to address those questions. Here the reviewer deals with the conceptualization and operationalization of constructs, the specificity versus generality of conclusions to be drawn, and the question of whether to conduct a review which tests hypotheses on the basis of "s tudy-generated evidence ~ or a review which proposes hypotheses on the basis of "review-generated evidence." Studygenerated evidence comprises information about effects examined within studies, such as treatment effects or the relationships of critical sub ject characteristics to treatment effects.
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The threats-to-validity approach involves determining whether each study in the review is sub ject to any of a number of threats to validity (such as those listed by Campbell
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Mental Practice 12 a n d S t a n l ey , 1 9 6 3 ) a n d th e me th o ds -d e s c r i p t i on app r oa ch i n vo 1 ve s the description of the features of study design via coding of the primary researchers' descriptions of the methodology of the studies .
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Glass ~ s popularization of the effect size, or standardized mean difference, as a measure of treatment effect that could be compared across studies using nonidentical instruments or measures, was the breakthrough that allowed the broad application of quantitative research synthesis techniques in the social and behavior sciences. The effect size for a comparison between the experimental and control groups in a study is the standardized mean difference yE ye where yE and yC are the _ _ respectively' and S is the common populat ion Glass proposed using t Hedges ( 1981)
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Thus, an effect size of 0.75 indicates that the means of the experimental and control groups differ by three fourths of one standard deviation. Another way to interpret the effect size is in terms of the performance of any average sub ject in the control group.
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When the reviewer considers a set of k studies, the parameters ol, ..., Ok are the population values about which inferences are made when sample effect sizes are analyzed.
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Statistical analyses designed specifically for effect sizes not only avoid the statistical problems of traditional analysis methods, but also provide tests of the adequacy of proposed models for the effect sizes which are not available from traditional methods. Rather than detail the statistical theory for the effect-size analyses, which is presented clearly by Hedges (e.g., Hedges, 1982a,b; Hedges & Olkin, 1985)
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Similarly, methods for identifying outliers provide ways to assess the impact of the omission of the outliers on the data analysis. effect sizes (model 3)
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In this approach tests of model 'adequacy' are often accompanied or replaced by estimates of residual variation in effects. Another approach to the analysis of effect sizes, which is often combined with those mentioned above, involves the identification of outliers, or unusual effect-size estimates.
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examined only the comparison of mental practice to no practice at all. Second, our present study will improve upon the earlier review by Feltz and Landers (1983)
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used the typical experimental versus control effect size, contrasting motor-skill performance between mental-practice and control groups. In our reanalysis, we will use separate effect sizes for the mental practice and control groups (as well as for combined mental and physical practice groups)
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From this search we identified 60 unpublished sources, 48 of which were obtainable and 48 published sources, all of which were obtainable. This resulted in a total of 96 distinct sources that were retrieved and identified as having examined the effects of some form of mental practice on motor performance.
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, respectively, for the 1th person in the With sample of the ith study. If a study examines the pretest and posttest motor-skill performance of sub jects in mentalpractice and control groups, it has two independent samples .
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Thus a difference-score effect size of 0.75 for a mental practice group indicates that the average subject in that group increased his or her performance by three-fourths of one standard deviation. If the skill in question were basketball jump shots, and the standard deviation of the number of pretreatment shots made was 10, then the average change is easily seen to be 7.5 additional shots made.
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The Wills (1966) study measured 8 outcomes for 12 independent samples of sub jects.
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. The values of r used f or the f our treatment groups were r = +.69 for control groups, r = +.64 for the mental practice groups, r = +.20 for the physical practice groups, and r = +.16 for the combined mental/physical groups.
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We also computed some effect sizes by approximating the value of Sg with the pooled within-groups mean square from a gain-score analysis of variance. Thus, with this method, we used the same standard deviation f or all groups resulting from one art icle or s tudy .
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Sub ject's sex was not found to be important in moderating the effect of mental practice and was, therefore, not coded in our review. Because difference-score effect sizes were computed in our analysis, the design characteristics used by Feltz and Landers were not appropriate.
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Comparisons that had not been made previously were between studies using different types of dependent measures and between studies using sub jects with different levels of imagery ability. The continuous predictor variables that were investigated were number of practice sessions and number of practice trials per session or length of each practice session in seconds.
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study was eliminated because it was the only study that measured muscular endurance. Consequently the physical practice sample in this study had extremely high effect sizes.
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The test for differences among mean effect sizes for the treatment groups is given by HB · which is also a chi-square variable, with 3 degrees of f reedom. We conclude that the f our
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. The average weighted change-score effect size for mental practice groups (0.47)
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For the length of practice per session variable which was measured in terms of number of practice trials, the overall models were significant for control, mental practice and physical practice groups with the control group having the only nonsignificant chi square for model fit. Although the control group regression analysis was significant and showed good fit, none of the individual polynomial predictors were significant using a Z test.
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. The overall learning, as indicated by the magnitude of the difference in pretest to posttest effect sizes, is of similar magnitude to the overall mental practice effect size (0.48)
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These results support the general findings in the literature that physical practice is a more effective learning strategy than mental practice (Weinberg, 1982)
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study, only one of the three tasks examined showed differences among the following ratios of physical practice to mental practice trials: 8:0, 6:2, 4:4, and 2:6. The 8:0 and 6:2 ratios had the greatest improvement in time-on-target scores with means of 4.37 and 4 .43, 2 For task measures of time-on-target/in balance, combined practice actually had a larger difference score effect size than either physical or mental practice.
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may be valid, but only if the ratio of the physical to mental practice trials is at least 75:25 .
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Mental Pract ice 37 Table 1 Features of Studies Study Feature C at e g 0 ri e s Treatment (Type of Practice Task Types Type of Dependent Measure Time of Posttes t Sub je c t Age Gr oup s Sub je ct Expe rience Sub ject Imagery Ability Control Ment al Pra ct ice Physical Practice Ment al/Phy s ice 1 Pra ct ice M ot 0 r Cogn i t ive St rength Endu ra nce Ac cu ra cy Speed St rength Power Form D i s t a n ce Time on Target Time in Balance En du ran ce Imme di ate ly Delayed Elementsry High School College A du 1 t Novice Expe ri ence d Low High after practice
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Table 1 Feature s _ Studie s M e nt a 1 P ra c t i c e 38 ( C on t i nu e d ) Study Feature C a t e g 0 ri e s Effect Size Computation Study Date Numbe r of Pra ct ice Ses s ions Length of Practice (Trials or Secs.
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- ~ Id a: ~ o P4 o ~ v Id so us · ~ v o In : A)
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In us ~ 0 a o ~ v bo In 0 · v a Id 0 In v: · ~ v x o ~ at u]
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Mental Practice 41 ~ In ~ ox 0 v to u: · ~ 0 u, In ~ oh · x 0 z co v: v c; ct so :~ a v u' ~ v u s 0 c' can a u: to ~5 In c: 0 so u: In In 0 an u, c: ct c: _ c; ~ ~ ~ can ct ~ ~ ~ ~ co ~ ~ ~ ~ ~ In ~ u' ~ £ £ ~ E E E ~ ~ 0 c~ L~ ~ 0 0 _ ~ t_ _ ~ 1— C~ ~ C~ u~ C - )
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M en t a 1 P r a c t i c e 42 In 0 ~ 0 P4 0 ~ to ~ so us · ~ ~ 0 ct so u: us u, · ~ cow x 0 0 u: u v c: so so a 0 c; cn cam c: 0 can cam a u' in ~ 0 in A, in ct cam ~ ~ ~ ~ 0 ~ ~ ~ ~ ~ ~ 0 0 ~ ~ ~ ~ ~ c: E ~ E ~ ~ ~ ~ E ~ E 0 0 ~ 0 s" ~ ~ u~ _ C~ '' C~ ~ Z ~ U^' ~ _ _ _ 'l oo ~ o0 \0 ~ ~ ~n ~ 0 ~t _ ~ _ C~ O O X O O Z; Z ~1 Z Z E s" E~ s" Ct o X o o o Z ~ :~ Z .
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Mental Pract ice 43 ct us a' ~ 0 ~ 0 0 ~ cat v cat us · ~ c; 0 ~ us p4 co In · x 0 Lo Z In u: cat cat so c: o c, In so 0 ~ cay o ~ cat ED us on At: E cat EN a, a, E ~ cot x us It cat cat so ~ Jo 0 oo cot LO 0 x 0 z ~ z u, :e ~ o o ~ ~ o o ~: ~ ~: c~ ~ ~ ~ P4 c~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~o ~ ~ 0 - - - - - ~c .
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Mental Pract ice 44 u so u' :: sac 0 ~ N · U: Ct ~ V C)
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Mental Pract ice 45 so al en tic 0 ~ N · U: Cal al C: Cal U: V U]
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M en t ~ 1 P r a c t i c e 46 in Hi: tic 0 ~ N · U: ~ V V C
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Mental Practice 47 .
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Mental Practice 48 a Hi: Tic 0 ~ N U]
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Table 3 Treatment Group Differences Among Effect Sizes Mental Practice 49 Test of Mean effect-size Source df Homogeneity p estimate (s.e. Total 221 788.32 .001 0.43 (0.02~*
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M e n t a 1 P ra c t i c e 50 Table 4 Analysis of Change in Type of Task by Treatment Group Test of Mean effect-size Source df Homogeneity p estimate (s.e.
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M e nt a 1 P ra c t i ce 51 Tab le 5 Analysis of Change in Type of Measure by Treatment Group for Motor Type Tasks Test of Mean effect-size Source df Homogeneity p estimate (s.e.
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Tab le S M e nt a 1 P ra c t i ce 52 Analsis of Change ~n Type of Measure by Treatment Group for Motor Type Tssks ( t;ontinueu ) Tes t of Mean ef f e ct -s i ze Source df Homogeneity ~ estimate (s.e.
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of Practice Trials ~ _ Cont rol Mental Practice P by s i ca 1 P ra c t i ce Me ntal/Phys i Cal 4 2.13 23 47.79*
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1962 The effect of physical practice, mental practice, and ~ . _ ~ mental-physical practice on the development of a motor skill.
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Crank, J.M. 1967 The effect of physical practice, mental practice, and physical-mental practice on the development of arm strength.
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1983 The ef f ects of mental practice on motor skill learning a n d p e rf or ma n c e : A met a -a na ly s i s . Jo u rna 1 0 f Sp 0 r t Psychology, _, 25-57 .
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1982b Fitting categorical models to effect sizes from a series of expe riments . Journal of Educational Statistics, 7, 119-137.
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1961 Effects of mental practice and physical practice upon muscular endurance. Research Quarterly, 32, 47-54.
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LaLance, R.C., Jr. 1974 A comparison of traditional instruction, mental practice, and combined physical-mental practice upon ~ .
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G.E. Negative and positive mental practice in motor skill acquisition.
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Ri ch a r ds on, A . 1967a Mental practice: A review and discussion.
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1966 The effect of mental practice and physical practice in ~ _ . ~ _ S ei de r ma n 1 9 8 3 Sheldon, 1 9 6 3
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1968 A comparison of the effects of physical and mental practice in learning 8 motor skill. Research Quarterly, 39, 714-720.
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1978 Learning a complex skill: Effects of mental practice, physical practice, and imagery ability. International Journal of Sport Psychology, 10, 71-78.
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1965 The effect of mental practice and physical practice on learning a motor skill. Unpublished master's thesis' Arkansas State College.
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