Frequency-dependent performance and handedness in professional baseball players (Homo sapiens)

I used data on handedness and pitching and hitting performance in annual cohorts of professional baseball players (1957-2005) to test the hypothesis that handedness among pitchers was subject to negative frequency-dependent selection. As predicted by this hypothesis, right-handed pitchers were more successful (i.e., opposing batters hit more poorly against them) when they were relatively rare in the population. Contrary to the predictions of this hypothesis, however, left-handed pitchers were more successful when they were relatively common. Both right- and left-handed batters performed better in years dominated by right-handed pitchers, despite the fact that right-handed batters perform relatively poorly against right-handed pitchers. I suggest that batters form cognitive representations based on pitcher handedness, and that these representations are strengthened by repeated exposure or priming. When the pitcher handedness polymorphism is more balanced (e.g., 67% right-handed, 33% left-handed), these cognitive representations are less effective, which leads to decreased batting averages and improved performance by all pitchers. Furthermore, these cognitive representations are likely to be more critical to the success of right-handed hitters, who have reduced visuomotor skills relative to left-handed hitters.     

Visual on- and off-latencies and handedness

Ten Ss served in this experiment, five right-handed and five left-handed. Every S was tested in a perceived-order situation and by the up-and-down method to determine the relative on-latency for a visual test stimulus. i.e, (ON-Lat for lest stimulus involving right hemisphere- ON-Lat for standard stimulus involving left hemisphere) and to determine a similarly defined relative off-latency for the same test stimulus. The algebraic difference between the relative on-latency measure and the relative off-latency measure was then found. Data from a previous study had suggested that this “on-off difference” was characteristically positive for left-handed Ss and negative for right-handed Ss. The present data agree. The left-handed Ss were found to differ significantly from the right-handed Ss in the magnitude of the on-off difference. This outcome appears important as a possible clue to functional interhemispheric differences related to handedness.     

The time course for language acquisition in biologically distinct populations: evidence from deaf individuals

The present study provides evidence that individuals who have different patterns of cerebral lateralization and who develop along different maturational time courses can attain comparable levels of language proficiency. Right-handed individuals with left-handed family members (left-handed familials, LHFs) showed a shorter sensitive period for language acquisition than did right-handed individuals with only right-handed family members (right-handed familials, RHFs). The shorter sensitive period for LHFs may be due to a focus on non-linguistic, word-based conceptual information during language acquisition. RHFs may focus on grammatical relations during language acquisition, which matures later than lexical knowledge. This suggests that there may be different patterns of cerebral lateralization for language in all normal populations as a function of familial handedness.     

Handedness and spatial ability in children: further support for Geschwind's hypothesis of "pathology of superiority" and for Annett's theory of intelligence.

Spatial ability of 60 left-handed and 60 right-handed school children was investigated using a battery of nine tasks. The results do not agree with Levy's (1969, 1976) theory predicting spatial inferiority of left-handed individuals. Instead, higher performance by left-handed children provided further support for Annett's (Annett & Manning, 1989) theory on intelligence and for Geschwind's (Geschwind & Galaburda, 1985) hypothesis of "pathology of superiority." The distinction of left-handed and right-handed individuals into familial and nonfamilial groups appeared to be psychologically equivocal according to our results.     

On the advantage of being left-handed in volleyball: further evidence of the specificity of skilled visual perception

High ball speeds and close distances between competitors require athletes in interactive sports to correctly anticipate an opponent's intentions in order to render appropriate reactions. Although it is considered crucial for successful performance, such skill appears impaired when athletes are confronted with a left-handed opponent, possibly because of athletes' reduced perceptual familiarity with rarely encountered left-handed actions. To test this negative perceptual frequency effect hypothesis, we invited 18 skilled and 18 novice volleyball players to predict shot directions of left- and right-handed attacks in a video-based visual anticipation task. In accordance with our predictions, and with recent reports on laterality differences in visual perception, the outcome of left-handed actions was significantly less accurately predicted than the outcome of right-handed attacks. In addition, this left-right bias was most distinct when predictions had to be based on preimpact (i.e., before hand-ball contact) kinematic cues, and skilled players were generally more affected by the opponents' handedness than were novices. The study's findings corroborate the assumption that skilled visual perception is attuned to more frequently encountered actions.     

Generalizing everyday memory: Signs and handedness

Memory for frequently encountered road signs was investigated. In Experiment 1, the average level of recall of road sign features was found to be only 47%. In Experiment 2, more left-handed than righthanded people recalled that a walking figure faces right on one sign, whereas more right-handed than left-handed people recalled that a digging figure faces left on another sign. Performance thus reflected not a difference in level of mnemonic ability between left-handed and right-handed groups but instead the compatibility between group and task. In Experiment 3, participants were asked to draw any figure walking and any figure digging, with a pattern of results similar to that of Experiment 2. It is suggested that handedness effects in recall are mediated by motor imagery.     

Spatial ability and handedness

The relationship between preferred handedness and spatial visualization was examined for 124 female and 229 male undergraduate students. Handedness and spatial ability were used in the design as continuous variables. Other variables examined were sex of subject and family history of sinistrality. Spatial ability was found to be systematically related to measured handedness, familial left-handedness, and sex of subject. Males outperformed females at all levels of handedness. The lowest performance was obtained by subjects who were either extremely left-handed or extremely right-handed. The highest scores were obtained by individuals with left-handed relatives and whose handedness scores were in the range considered mixed or slightly right-handed. The results suggest that decreased hemispheric specialization is associated with increased spatial ability.     

The German Adaptation and Standardization of the Personality Assessment Inventory (PAI)

An attempt was made to evaluate the relationship between left-handedness and oppositional tendencies through the use of the White Space (S) response on the Rorschach. Right and left-handed males were administered the Rorschach, and it was found that the left-handed subjects gave significantly more S responses than did the right-handed males. It was felt that the results of this study indicated the existence of a relationship between hand-preference and oppositional tendency. Caution was raised concerning the assumption that oppositional tendencies foster left-handedness. It was pointed out that opposition could also be produced by being left-handed.     

Sensitivity to laterality as a function of handedness

This study tested the hypothesis that left-handed individuals are more aware than right-handed individuals of others' handedness. 18 left-handed and 18 right-handed college students were shown a drawing of 8 children at a party. Seven children held objects in the left hand, while one held an object in the right hand. After 2 1/2 min. the drawing was removed and subjects answered 15 questions about its contents. Included were 2 questions asking how many children were holding something in the right or left hand. Compared with right-handed subjects, left-handed subjects reported significantly more children holding something in the left hand and significantly fewer holding something in the right hand. The two groups did not differ on any other questions.     

Manual asymmetry in weight discrimination: hand or spatial-field advantage?

Sixty subjects who were either left-handed or right-handed performed one-handed weight discrimination using their left and right hands in the left and right spatial fields. Differential thresholds, for the left and right hands of both left-handed and right-handed subjects, were found to be lower in the spatial field contralateral to the ear which proved superior in a dichotic listening test. It is concluded that manual asymmetry for weight discrimination results primarily from the mapping of sensorimotor events in the spatial fields onto contralateral cerebral cortex, with an advantage in the spatial field contralateral to the nonlanguage cerebral hemisphere.     

Right hemisphere specialization for color detection

Three experiments were carried out to investigate hemispheric asymmetry in color processing among normal participants. In Experiment 1, it was shown that the reaction times (RTs) of the dominant and non-dominant hands assessed using a visual target presented at the central visual field, were not significantly different. In Experiment 2, RTs of ipsilateral hands to lateralized chromatic stimuli revealed that the processing time was 17 ms shorter in the right hemisphere (RH) than that in the left hemisphere among the right-handed participants, whereas no significant difference was found among the left-handed participants. On the other hand, RTs to lateralized achromatic stimuli showed no such asymmetry among both the right- and left-handed participants (Experiment 3). These findings strongly suggest RH superiority for detection of color among right-handed individuals.     

Hemispheric differences in a letter classification task

The experiment examined hemispheric differences in same-different judgments for unilaterally presented letter pairs which could be classified as “same” on the basis of name identity (NI, e.g., Aa) or physical identity (PI, e.g., AA). Two groups of Ss were tested, a right-handed group and a predominantly left-handed group. The experiment employed a reaction time measure, and fixed the duration of brief exposures to yield an overall performance level of 90% correct. Analysis of the results focused on the difference between RTs for the NI matches and for the PI matches in each hemisphere. The method allowed differences in cognitive processing to be assessed while sensory and response factors were minimized. The right-handed group all showed a smaller mean NI-PI difference in the left hemisphere (84 msec) than in the right hemisphere (181 msec). The left-handed group showed smaller and less consistent differences, but the group as a whole had a reversed asymmetry, with a mean NI-PI difference of 128 msee in the left hemisphere and 90 msec in the right hemisphere.     

Right-left discrimination: effects of handedness and educational background

The present study investigated right left discrimination, with a paper-and-pen test with cartoon figures. The test consisted of line drawings of a person with no, one, or both arms crossing the vertical axis of the body in the figure. The subjects' task was to mark with a pencil, as fast as possible, which was the right or left hand in the figure. The line drawings were viewed from the back, from the front, or randomly alternating between the back and front views. Two studies were conducted. The first consisted of 393 adults: 153 males and 240 females; 338 right-handers and 55 left-handers. The results showed that the males performed better than the females. The left-handers and the right-handers performed equally well. However, the left-handed males performed better than the right-handed males. There was no difference in performance between the right-handed and the left-handed females. The second study consisted of 175 right-handed college students: 63 psychology students. 54 medical students, and 58 law students. The main finding was that the medical students performed better than the psychology students for all figure orientation subtests and for all arm positions. In comparison with the law students, the medical students performed at the same level on the back view subtest, but they performed better on the front view subtest and on two out of three arm positions on the alternating view subtest.     

Asymmetrical Body Perception: A Possible Role for Neural Body Representations

ABSTRACT— Perception of one's body is related not only to the physical appearance of the body, but also to the neural representation of the body. The brain contains many body maps that systematically differ between right- and left-handed people. In general, the cortical representations of the right arm and right hand tend to be of greater area in the left hemisphere than in the right hemisphere for right-handed people, whereas these cortical representations tend to be symmetrical across hemispheres for left-handers. We took advantage of these naturally occurring differences and examined perceived arm length in right- and left-handed people. When looking at each arm and hand individually, right-handed participants perceived their right arms and right hands to be longer than their left arms and left hands, whereas left-handed participants perceived both arms accurately. These experiments reveal a possible relationship between implicit body maps in the brain and conscious perception of the body.     

Selective activation effects of concurrent verbal and spatial memory loads in left-handed and right-handed adults

Thirty-two left-handed subjects, divided into four groups according to sex and familial sinistrality, and 16 right-handed subjects without familial sinistrality (8 male, 8 female) participated in a tachistoscopic unilateral letter-identification task with concurrent verbal- and spatial-memory loads. Across groups, a significant right visual field advantage for letter-identification was found. In the majority of both left-handed and right-handed subjects, the concurrent verbal-memory load resulted in a selective activation, with the right visual field performance showing improvement. However, the group of left-handed males with a positive family history of sinistrality gave less evidence of selective left-hemispheric activation as a consequence of the verbal-memory load. The concurrent spatial-memory load did not result in a consistent pattern of selective activation.     

Hemifield independence in the left handed

Tachistoscopically presented arrays containing either a single word or two words in different configurations were given to left- and right-handed subjects. Several measures indicated hemifield, and by implication, hemispheric independence for word recognition was more likely to be found among left- than right-handers. Differences within the left-handed group associated with the presence of family sinistrality and writing posture were also found. Results were discussed with respect to the view that bilateral representation of language frequently occurs in left-handed adults.     

Evaluation of some tasks used for specifying handedness and footedness

Healthy men (n = 42) and women (n = 45) who were right-handed and men (n = 21) and women (n = 20) who were left-handed were studied. Men's mean age was 21.1 +/- 3.5 yr. and women's 20.7 +/- 3.1 yr. These students in various faculties reported they were right- or left-handed. Then their hand and foot preferences (handedness and footedness) were ascertained by asking each of the subjects to perform 11 tasks for handedness and 9 tasks for footedness. A discriminate function analysis test showed that each of the 11 tasks used for assessing their self-reported handedness was significant, but, of the 9 tasks used for assessing self-reported footedness, only 7 were significant. Strength of the hand or foot played no role in reports of handedness or footedness. A combination of four tasks, such as pulling a door, pushing a door, holding an object, and hammering a nail, on which the maximum number of subjects performed with the right or left hand, depending upon their self-reported handedness, would be ideal for ascertaining handedness. A combination of three tasks, namely, kicking a football, pushing an object with the foot, and stamping on the ground, would be ideal for ascertaining footedness.     

Laterality, hand preference, and human spatial ability.

6 left-handed females scored significantly below 60 right-handed females on a test of spatial visualization (p less than .005). 13 left-handed males showed a higher mean score than 33 right-handed males on the spatial test, although this difference was not statistically significant. These results are consistent with the hypothesis that the left cerebral hemisphere is of greater relative importance to spatial functioning in females than males.     

Intrahemispheric response competition between vocal and unimanual performances in normam adult human males.

Subjects balanced a dowel rod vertically on the left and right index finger singly and while simultaneously repeating phrases. With right-handed subjects who had no left-handed relatives, concurrent verbalization shortened right- but not left-handed balancing. Increased phonetic difficulty of the phrases produced an increased decrement on right-handed balancing, but left-handed balancing was unchanged; it also produced more verbalization errors on trials with the right hand, but not with the left. Concurrent verbalization shortened balancing duration with both hands of left-handers. Right-handers with left-handed relatives produced variable results. Concurrent humming also selectively interfered with right-handed balancing. It was concluded that the results conform to an interpretation based on intrahemispheric interference between incompatible, simultaneously produced sets of responses.     

Visual — motor organization and memory in the right-handed and the left-handed child: A comparative neuropsychological approach

The visual-motor organization of the child was investigated with the primary aim of defining the relationships between the cognitive changes taking place during problem solving (mnemonic reproduction of a complex figure) and the structural functional elements involved. The sample consisted of 840 right-handed and left-handed children aged 5.5 to 12.5 years, who were group-matched on the basis of age, sex, and hand preference. Statistical evaluation revealed significant differences for boys and girls across the various age groups. Statistically significant differences also appeared between right- and left-handed children. The differences in performance can be attributed to neuropsychological functional differences between right-and left-handed children.