The Success of Sinister Right-Handers in Baseball

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Supporting data from Left-handedness and time pressure in elite interactive ball games

Excel file that contains raw data on rankings, handedness and time interval

Left preference for sport tasks does not necessarily indicate left-handedness: sport-specific lateral preferences, relationship with handedness and implications for laterality research in behavioural sciences.

In the elite domain of interactive sports, athletes who demonstrate a left preference (e.g., holding a weapon with the left hand in fencing or boxing in a 'southpaw' stance) seem overrepresented. Such excess indicates a performance advantage and was also interpreted as evidence in favour of frequency-dependent selection mechanisms to explain the maintenance of left-handedness in humans. To test for an overrepresentation, the incidence of athletes' lateral preferences is typically compared with an expected ratio of left- to right-handedness in the normal population. However, the normal population reference values did not always relate to the sport-specific tasks of interest, which may limit the validity of reports of an excess of 'left-oriented' athletes. Here we sought to determine lateral preferences for various sport-specific tasks (e.g., baseball batting, boxing) in the normal population and to examine the relationship between these preferences and handedness. To this end, we asked 903 participants to indicate their lateral preferences for sport-specific and common tasks using a paper-based questionnaire. Lateral preferences varied considerably across the different sport tasks and we found high variation in the relationship between those preferences and handedness. In contrast to unimanual tasks (e.g., fencing or throwing), for bimanually controlled actions such as baseball batting, shooting in ice hockey or boxing the incidence of left preferences was considerably higher than expected from the proportion of left-handedness in the normal population and the relationship with handedness was relatively low. We conclude that (i) task-specific reference values are mandatory for reliably testing for an excess of athletes with a left preference, (ii) the term 'handedness' should be more cautiously used within the context of sport-related laterality research and (iii) observation of lateral preferences in sports may be of limited suitability for the verification of evolutionary theories of handedness

Directionality in Aesthetic Judgments and Performance Evaluation: Sport Judges and Laypeople Compared

Left-to-right readers are assumed to demonstrate a left-to-right bias in aesthetic preferences and performance evaluation. Here we tested the hypothesis that such bias occurs in left-to-right reading laypeople and gymnastic judges (n = 48 each) when asked to select the more beautiful image from a picture pair showing gymnastic or non-gymnastic actions (Experiment 1) and to evaluate videos of gymnasts’ balance beam performances (Experiment 2). Overall, laypeople demonstrated a stronger left-to-right bias than judges. Unlike judges, laypeople rated images with left-to-right trajectory as more beautiful than content-wise identical images with right-to-left trajectory (Experiment 1). Also, laypeople tended to award slightly more points to videos showing left-to-right as opposed to right-to-left oriented actions (Experiment 2); however, in contrast to initial predictions the effect was weak and statistically unreliable. Collectively, judges, when considered as a group, seem less prone to directional bias than laypeople, thus tentatively suggesting that directionality may be an issue for unskilled but not for skilled judging. Possible mechanisms underlying the skill effect in Experiment 1 and the absence of clear bias in Experiment 2 are discussed alongside propositions for a broadening of perspectives in future research

Relationship between sport-specific lateral preferences and handedness.

<p><i>Note:</i> For the calculation of <i>r</i>_pb we excluded ‘no preference’ responses for the sport-specific tasks. The majority of relationships were significant with <i>p</i><.001. To facilitate reading the table, only non-significant relationships or significant relationships with <i>p</i>-values larger than.001 are indicated as follows: ^ns<i>p></i>.05, ^a<i>p</i><.01, ^b<i>p</i><.05. Please also note that we additionally clustered the participants into left- (LS <0) and right-handers (LS ≥0) and that we used these classifications to determine the relationship between handedness and sport-specific lateral preferences based on the calculation of phi coefficients Φ. In two calculation scenarios, once with inclusion and once with exclusion of ‘no preference’ responses, similar relationships as those reported above were found (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105800#pone.0105800.s003" target="_blank">Table S3</a> for a summary of the results).</p

Left preferences for sport-specific tasks overall and differentiated by sex.

<p>Left preferences for sport-specific tasks overall and differentiated by sex.</p

Left- and right-handers' lateral preferences for sport-specific tasks.

<p><i>Note</i>: For each sport-specific task, ‘no preference’ responses are excluded. Participants were classified as left- and right-handers based on their individual LS values (i.e., left-hander if LS <0 and right-hander if LS ≥0). ‘L’ and ‘R’ indicate left and right preference for a sport task.</p

Left-Handedness in Professional and Amateur Tennis

<div><p>Negative frequency-dependent effects rather than innate predispositions may provide left-handers with an advantage in one-on-one fighting situations. Support mainly comes from cross-sectional studies which found significantly enhanced left-hander frequencies among elite athletes exclusively in interactive sports such as baseball, cricket, fencing and tennis. Since professional athletes’ training regimes continuously improve, however, an important unsolved question is whether the left-handers’ advantage in individual sports like tennis persists over time. To this end, we longitudinally tracked left-hander frequencies in year-end world rankings (men: 1973–2011, ladies: 1975–2011) and at Grand Slam tournaments (1968–2011) in male and female tennis professionals. Here we show that the positive impact of left-handed performance on high achievement in elite tennis was moderate and decreased in male professionals over time and was almost absent in female professionals. For both sexes, left-hander frequencies among year-end top 10 players linearly decreased over the period considered. Moreover, left-handedness was, however, no longer seems associated with higher probability of attaining high year-end world ranking position in male professionals. In contrast, cross-sectional data on left-hander frequencies in male and female amateur players suggest that a left-handers’ advantage may still occur on lower performance levels. Collectively, our data is in accordance with the frequency-dependent hypothesis since reduced experience with left-handers in tennis is likely to be compensated by players’ professionalism.</p> </div

Frequency of left-handed performers in amateur tennis.

<p>Left-hander frequencies in (A) male and (B) female amateur tennis depending on performance level (1 =  highest level, …, 23 =  lowest level). Data were fitted to logarithmic functions with <i>R</i>² = .48 (men) and <i>R</i>² = .34 (ladies), respectively (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049325#pone.0049325.s007" target="_blank">Table S7</a>).</p