Reproducing the end location of a positioning movement: the long and short of it

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of the starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

Reproducing the End Location of a Positioning Movement

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

The handedness of Leonardo da Vinci: a tale of the complexities of lateralisation

The handedness of Leonardo da Vinci is controversial. Although there is little doubt that many of his well-attributed drawings were drawn with the left hand, the hatch marks of the shading going downwards from left to right, it is not clear that he was a natural left-hander, there being some suggestion that he may have become left-handed as the result of an injury to his right hand in early adulthood. Leonardo's lateralisation may be illuminated by an obscure passage in his notebooks in which he describes crouching down to look into a dark cave, putting his left hand on his knee, and shading his eyes with his right hand. We carried out a questionnaire survey, using 33 written and photographic items, to find whether this behaviour was typical of right handers or left handers. In fact the 'Leonardo task' showed almost no direct association with handedness, meaning that it contributes little to the immediate problem of elucidating Leonardo's handedness. However, the lateralisation of the task did relate to other aspects of behavioural laterality in surprisingly complex ways. This suggests that individual differences in handedness, and behavioural laterality in general, have a structural complexity which is not fully encompassed by simple measures of direction or degree of handedness.     

基诺族左右利手分布的再调查

1981年,全国利手研究协作组对基诺族的左右利手分布作了首次调查。这次调查的结果是,基诺族全部是强右利手。这是一个非常特殊的结论。为此,一九八九年我们对基诺族的左右利手分布又作了一次调查。调查发现,基诺族并不都是强右利手,他们当中既有一般的右利手,也有混合利手,还有左利手,甚至有1.79％的强左利手。基诺族的左利率高于汉族,但与其他少数民族接近。基诺族的左利率偏高占其传统文化有关。全国利手研究协作组的调查结果应该修正。     

利手与语言功能偏侧化的遗传模型

利手与语言功能偏侧化现象不仅具有跨文化一致性和发生、发展上的关联性, 还具有明显的生态学优势, 从遗传角度探讨它们的成因是必要的。早期遗传模型认为, 存在一对等位基因分别决定左、右利手。当代单基因模型则将语言功能偏侧化也纳入进来, 认为等位基因不仅可以决定具有方向性的偏侧化, 而且可以使偏侧化有一定几率向左或向右。在这个框架下形成了方向-随机等位基因模型、X-连锁隐性基因模型和右侧位移理论, 它们对等位基因的位置和功能有不同表述, 对利手的划分标准、性别差异以及遗传和环境的关系也有不同阐释。今后需加强对语言偏侧化的数据验证, 进一步阐明语言感知、理解与利手的关系, 并注重基因怎样决定表型、基因多效性和多基因合作等问题的研究。     

Conditional handedness: Handedness changes in multiple personality disordered subject reflect shift in hemispheric dominance

This study investigates whether the host personality (Pe) and the primary alterpersonality (Pa) of a woman with multiple personality disorder are controlled by the left and right hemispheres, respectively. Results support the hypothesis. Behavioral and preference measures indicate that Pe is strongly right handed and Pa is left handed. Verbal and musical dichotic tests show significantly greater accuracy for stimuli presented to the left ear for Pa and to the right ear for Pe. It is concluded that shifts in hemisphericity involve redistribution of attentional resources and callosal suppression. “Conditional handedness” is proposed as a handedness subtype, characterizing persons who alternate personalities and consistently display alternate hand preferences linked to specific personality characteristics.     

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.     

Do Unilateral Right and Left Face Contractions Induce Positive and Negative Emotions? A Further Test of Schiff and Lamon's (1989) Hypothesis

Schiff and Lamon (1989) proposed that unilateral face contractions induce positive or negative changes in emotion depending on the side of contraction; support for this proposal, however, has been mixed. In a new test, 40 right-handed and 38 left-handed men performed four alternating face contractions (LRLR or RLRL) and, after each one, completed a different version of the Depression Adjective Checklist (Lubin, 1994). A repeated-measures ANCOVA failed to reveal any significant effect of side of face contraction or handedness on direction of emotion change. Instead, regardless of side of contraction, the subjects' negative emotional state increased significantly across the four contractions with the degree of change being significantly related to the subjects' reported level of difficulty in holding the contraction irrespective of whether the more difficult side was the left or the right.     

Mixed-sided individuals with neuroticism sustain more unintentional injuries in India

Previous research has shown a positive association between unintentional injury liability and non‐right‐handedness (especially mixed‐handedness). Research has also shown neuroticism to be one of the main predictors of unintentional injuries. In the present study we investigated the relationship of the three variables—frequency of unintentional injuries, side bias, and neuroticism. Further, the study aimed at extending the findings of previous studies establishing a relationship between non‐right‐handedness and unintentional injuries to a similar pattern in other domains of side bias—footedness, eyedness, and earedness. Data were collected from a large sample (N = 3474) using the side bias questionnaire, the shorter version of Maudsley's Personality Inventory, and an unintentional injury checklist. Results revealed positive correlations between the frequency of unintentional injuries and mixed‐sidedness, followed by left‐sidedness and right‐sidedness in each of the four domains of side bias. Furthermore, an increase in the frequency of unintentional injuries was observed for mixed‐sided and left‐sided individuals with higher levels of neuroticism.     

Comparative analysis of proprioception in left and right arms

Using the “kinaesthetic memory for the target” technique, differences in the accuracy of pointing to a target with the right and left arms are analysed. The effect of rotation of the head to left and right upon this process is also studied.

With the head normally orientated, it was found that pointing with the right arm is significantly better than with the left. Accuracy of pointing is greater with the target directly in front of the body than when it lies to either left or right side.

When the head is rotated, the direction of the pointing error is inversely related to the direction of rotation.

The study suggests that the precision of control over arm (in the absence of vision) is related to the varying ability of individual subjects to correlate limb movements with the prevailing orientation of the body, especially of the head and neck. This is additional to the influences of genetically-determined handedness and of the sensory input from the moving limb.     

Handedness and Reach-to-Place Kinematics in Adults: Left-Handers Are Not Reversed Right-Handers

The primary goal of this study was to examine the relations between limb control and handedness in adults. Participants were categorized as left or right handed for analyses using the Edinburgh Handedness Inventory. Three-dimensional recordings were made of each arm on two reach-to-place tasks: adults reached to a ball and placed it into the opening of a toy (fitting task), or reached to a Cheerio inside a cup, which they placed on a designated mark after each trial (cup task). We hypothesized that limb control and handedness were related, and we predicted that we would observe side differences favoring the dominant limb based on the dynamic dominance hypothesis of motor lateralization. Specifically, we predicted that the dominant limb would be straighter and smoother on both tasks compared with the nondominant limb (i.e., right arm in right-handers and left arm in left-handers). Our results only partially supported these predictions for right-handers, but not for left-handers. When differences between hands were observed, the right hand was favored regardless of handedness group. Our findings suggest that left-handers are not reversed right-handers when compared on interlimb kinematics for reach-to-place tasks, and reaffirm that task selection is critical when evaluating manual asymmetries.     

Bilateral tachistoscopic perception,handedness, and laterality: II. Nonverbal stimuli

Thirty-two Subjects were assigned to four groups on the basis of handedness (left or right) and familial sinistrality (absent or present). Their laterality patterns were investigated with a cued order-of-report paradigm. On each trial, Subjects saw a tachistoscopic presentation of two outline drawings of common objects, one drawing on the left of a central fixation point, one on the right. A centered arrowhead appeared with the pictures; the arrowhead pointed either left or right, and its direction indicated the order of report. The results for each group were discussed in terms of asymmetry for rate of processing and rate of decay, and in comparison with our earlier study of word recognition.     

Visuospatial reaching preferences of common marmosets (Callithrix jacchus): an assessment of individual biases across a variety of tasks

Using multiple measures of hand preference, the authors investigated lateralization at an individual level in 21 common marmosets. Despite showing group biases for sensory and communication functions, these same marmosets did not show a group bias in direction of lateralized hand use. Hand preferences were recorded on four novel reaching tasks requiring different levels of visual guidance and postural control. As found for simple food holding (with the same subjects), they displayed strong individual hand preferences but no group bias indicative of handedness. The strength of hand preference was influenced by task demands: stronger preferences were expressed when subjects adopted a suspended posture, and when "successful" versus "unsuccessful" foraging strategies were compared. Comparisons between visuospatial reaching and simple food holding preferences also revealed that half of the subjects displayed a division of function between the hands/hemispheres; subjects displayed opposing preferences in simple and visuospatial reaching, which would be beneficial for the performance of coordinated bimanual tasks. Given the apparent absence of a selective advantage for handedness, the authors suggest that hand preferences may reflect hemispheric dominance of other cognitive domains (i.e., temperament).     

The Body in Religion: The Spatial Mapping of Valence in Tibetan Practitioners of Bön

According to the Body‐Specificity Hypothesis (BSH), people implicitly associate positive ideas with the side of space on which they are able to act more fluently with their dominant hand. Though this hypothesis has been rigorously tested across a variety of populations and tasks, the studies thus far have only been conducted in linguistic and cultural communities which favor the right over the left. Here, we tested the effect of handedness on implicit space‐valence mappings in Tibetan practitioners of Bön who show a strong religious preference for the left, in comparison to an English group. Results showed that Bön right‐handers tended to implicitly associate positive valence more strongly with their dominant side of space despite strong explicit associations between the left and goodness in their religion. This pattern of results found in Bön participants was indistinguishable from that found in English speakers. The findings of the present study support the BSH, demonstrating that space‐valence mappings in people's minds are shaped by their bodily experience, which appears to be independent of space‐valence mappings enshrined in cultural conventions.     

Asymmetries in a unilateral flanker task depend on the direction of the response: the role of attentional shift and perceptual grouping

Four experiments were conducted using a flanker task with 1 distractor appearing either on the left or right side of a central target. Responses were made on a keyboard aligned parallel to the displays. A larger flanker effect was obtained when the distractor was on the same side as the response. Two factors account for this asymmetry. First, when the flanker and target are identical, the 2 form a group that is assigned a spatial tag, creating a form of the Simon effect on the basis of the compatibility between the response keys and the group. Second, preparation of a lateralized response appears to entail a shift of visual attention in the corresponding direction, thus enhancing processing of the flanker on the response side. Consistent with the 2nd hypothesis, participants were more likely to correctly recognize letters that were briefly presented at the distractor position on the same side as the response.     

左利手及其形成机制:生理、病理及心理学的视角

与右利手相比,左利手在人口中占少数,并且具有明显的性别差异,男性比女性多。左利手有时会表现出认知缺陷,同时在某些领域也具有优势。左利手形成机制比较复杂,既有遗传影响,也有生理、病理方面的原因,可能的因素包括早期脑损伤,各种出生风险因素,以及孕期激素水平等,还具有深刻的心理、社会根源。     

Aesthetic preference and lateral dominance

Aesthetic preferences for photographs with the main focal content either to the left or right of the photograph's center were examined in right- and left-handed subjects. Verbal responses or manual responses were required. In one experiment with 261 introductory psychology student-subjects, left-handers more often preferred photographs with the more important part on the left ("left-geared") than did right-handers. Exp. 2, involving 84 right-handed student subjects, showed that left-geared photographs presented on the left side were preferred more often than left-geared photographs presented on the right side, and left-geared photographs presented on the left side were more often chosen when a left-handed manual response was required. Interactions between handedness, position of the stimulus, language hemisphere, and response mode make it extremely difficult to ascertain whether the right hemisphere is really more involved in aesthetic decisions.     

Protective inhibition: A central factor in auditory fatigue

Summary A signal detection experiment was performed to investigate the sensitivity shift after stimulation with discontinuous octave-band noise of 95 dB (A). The influence of psychological factors on the sensitivity shift in the stimulated and the unstimulated ear was investigated in a two-factorial experimental design. In four independent groups of 12 Ss each, the psychological meaning of the noise and the side of sensitivity measurement were varied. Half of the Ss listened passively to the noise stimuli (control groups), the other half was made to believe that the noise signaled errors in a tracking task (experimental groups). After exposure of noise stimuli to the right ear the sensitivity of either the right or the left ear was determined. After exposure to noise the sensitivity of the stimulated ear was shown to be significantly more reduced in the experimental than in the control group. Thus, depending on the meaning of the noise physically identical stimuli produce sensitivity shifts of different amounts. After stimulation of the right ear with noise the sensitivity of the left ear remained completely unaffected. The sensitivity shift of the right ear did not persist as long as a threshold shift would have done. The hypothesis is that intensive auditory stimuli will produce negative feedback which protects — within certain limits — the stimulated ear from the fatiguing after-effects of overstimulation. The effectiveness of this protective inhibition depends on psychological factors.We are grateful to S. Jörg-Wagner for his competent handling of the experiment.     

Consistency of handedness, regardless of direction, predicts baseline memory accuracy and potential for memory enhancement

Research has shown that consistently right-handed individuals have poorer memory than do inconsistently right- or left-handed individuals under baseline conditions but more reliably exhibit enhanced memory retrieval after making a series of saccadic eye movements. From this it could be that consistent versus inconsistent handedness, regardless of left/right direction, is an important individual difference factor in memory. Or, more specifically, it could be the presence or absence of consistent right-handedness that matters for memory. To resolve this ambiguity, we compared consistent and inconsistent left- and right-handers on associative recognition tests taken after saccades or a no-saccades control activity. Consistent-handers exhibited poorer memory than did inconsistent-handers following the control activity, and saccades enhanced retrieval for consistent-handers only. Saccades impaired retrieval for inconsistent-handers. None of these effects depended on left/right direction. Hence, this study establishes handedness consistency, regardless of direction, as an important individual difference factor in memory.     

What the experimenter’s prime tells the observer’s brain

The presentation of a stimulus below the threshold of conscious awareness can exert an influence on the processing of a subsequent target. One such consequence of briefly presented “primes” is seen in the negative compatibility effect. The response time (RT) to determine the left—right orientation of an arrow (i.e., the target) is relatively slow if a prime is also an arrow whose direction corresponds to that of the target. When the direction of the arrow is opposite that of the prime, RTs are relatively fast. In four experiments, we examined whether the prime shifts attention from the location of the subsequent target and whether this attention shift influences target processing. Results showed that the prime does indeed move attention. The consequence of this attention movement is that the representation of direction is affected. Specifically, RTs to process an arrow are shorter if the arrow’s direction is compatible with the last shift of attention. Furthermore, this interference occurs at a conceptual level concerning the representation of left and right rather than at the motor planning level. We argue that a shift in attention brought about by the prime can create a negative compatibility-like effect.