This thesis presents an eclectic mix of studies which consider laterality in the context of previous findings of increased prevalence of Posttraumatic Stress Disorder (PTSD) in male combat veterans with non-consistent right hand preference. Two studies extend these findings not just to civilian populations and women, but to left handers and find that left, rather than mixed, handedness is associated with increased prevalence of PTSD in both general population and clinical samples, and to severity of symptoms in the former. To examine issues relevant to the fear response in healthy populations, a movie excerpt is shown to be theoretically likely to target the emotion of fear and to generate subjective and physiological (skin conductance) responses of fear. The film is used as a laboratory analogue of fear to examine possible differences in left and right handers in memory (for events of the film) and in an emotional Stroop paradigm known to produce a robust and large effect specifically in PTSD. According to predictions based on lateralisation of functions in the brain relevant to the fear response, left handers show a pattern of enhanced memory for visual items and poorer memory for verbal material compared to right handers. Immediately after viewing the film, left handers show an interference effect on the Stroop paradigm to general threat and film words and increased response latency compared to right handers, approaching performance of previously reported clinical samples with PTSD. A novel non-word Stroop task fails to show these effects, consistent both with accounts of interference as language processing effects and compromised verbal processing in PTSD. Unexpected inferior performance of females in memory for the film, contrary to previous literature, may also be amenable to explanations invoking compromised left hemisphere language functions in fear situations. In testing one theory of left handedness as due to increased levels of in utero testosterone, the 2D:4D (second to fourth digit ratio) provides mixed evidence in two samples. A possible association of more female-like digit ratios in males with PTSD is a tentative finding possibly relevant to sex differences in prevalence of PTSD. A critique of existing and inadequate theoretical accounts of handedness concludes the thesis and proposes a modification of the birth stress hypothesis to one specifically considering peri-natal trauma to account for the above findings. This hypothesis remains to be empirically tested.

Handedness is the most obvious expression of lateralized behaviour in humans. However, there is only limited knowledge about other forms of lateralized behaviour, e.g. preferential use of an eye and whether these may correlate with handedness. Thus to investigate this, 100 subjects (50 males and 50 females) between 11 and 80 years of age were assessed for their eye preference, eye dominance, visual acuity, and handedness. Eye preference was assessed by performing four different monocular tasks, eye dominance by performing the binocular Dolman test, visual acuity was assessed with a Snellen chart and handedness was surveyed using the Edinburgh Handedness Inventory. Regarding eye preference, the right eye was preferred by 69% of the subjects. 90 % of the subjects were consistent for their preferred eye across all four tasks. 66% of the subjects had a dominant right eye, 33% had left eye dominance and 1% could not be assessed using the Dolman test. 56% of the subjects differed in their visual acuity between both eyes, while 43% had the same visual acuity in both of their eyes. 86% of the subjects were right-handed while 4% were left handed and 10% were ambidextrous. Significant correlations were found between visual acuity and eye preference and between visual acuity and eye dominance. The study also found a positive correlation between handedness and eye preference. These results support the notion that there is a weak correlation between the different aspects of lateralized behaviour in humans.

Several studies have reported a strong bias in both human and non-human species for cradling their infants to the left side of the body. Most studies suggest that the main reason this phenomenon is the predominance of the right hemisphere of the brain for the processing of emotions and its transference, through brain laterality, to the left side of the body. Many other variables, including handedness, footedness, stress and depression have also been found to have some effect on cradling side. However, no study has been published for an Arab population. Given the strong religious and cultural belief of most Arabs that only the right hand should be used for most daily tasks, this study investigated the affect on cradling side of this habit, in addition to the factors named above. 369 Saudi citizens took part in this study. 234 lived in Saudi Arabia and 135 had lived in the UK for five or more years. 267 were women and 102 were men. Each answered a questionnaire which asked about their ‘preferred’ cradling side and then the 102 men were videotaped spontaneously cradling a real infant and an infant-like doll. Unfortunately, only the male sample could be videotaped due to restrictions on filming females in Saudi Arabia. The results confirmed those of previous studies by showing a very strong bias to leftside cradling. No difference was found between males and females in cradling a doll, or between the Saudi-based sample and the UK-based sample but the bias was significantly reduced in men. Apart from the influence of gender, the factors that reduced the cradling bias for a real infant were found to be lack of experience of parenthood, depression, stress and greater age of the infant. In cradling a doll, the most influential variables were handedness, footedness and depression. Further work is required on Arab samples, especially in examining spontaneous cradling by women and its relation to depression and stress. A mother’s mental state is known to affect the health of the infant and cradling side could be a useful filter for neonatal women who might require psychiatric treatment. Further research could also shed light on gender differences in the processing of emotion.

CiTonga speakers in Malawi describe dominant use of the left hand as distasteful and offensive in face-to-face multimodal interactions, communicative exchanges involving both oral-auditory and visual-gestural actions. They observe a left hand taboo on religious and social grounds, linking the right hand to "good" and the left hand to "bad". Despite this widespread perception, ciTonga speakers were often observed using their left hand and eschewing the taboo even in serious situations where politeness is a social imperative. In this study, I aim to resolve this paradox by arguing that the significance of left hand taboo is domain specific. To do this, I collected 101 multimodal interactions--over 50 hours of recording--through participant observation in Cifila and Kavuzi, where ciTonga is spoken as a native language. I analyzed the gestures in two domains of interaction: everyday rituals and ordinary talks. For both domains, flexibility of handedness is determined by a ranking of four different contextual constraints. I proposed a decision matrix to describe how the type and scale of a constraint can explain the permissiveness of left hand use. CiTonga kinesic signs can elevate to taboo status when they violate the handedness convention for interlocutors with distant social relationships, but over-producing deferential signs can create a social imbalance between close affiliates. Selecting an interaction-appropriate hand preference is therefore an integral part of ciTonga communicative competence. A study on taboo in multimodality shows the ways in which domain structure and purpose shape the application of large sociocultural ideologies to spontaneous interactions in daily life. / acase@tulane.edu

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-134). Also available for download via the World Wide Web; free to University of Oregon users.

This study explored how individuals categorized on handedness (being left or right hand dominant) reacted to having the vertical scroll bar of a web browser relocated to the left side of the screen. The relocation of the vertical scroll bar served as an alternative to the relocation of the prominent left aligned main navigation menu for most websites. Fifteen participants were recruited for the study. Each participant interacted with two versions of a web site in a modified browser to complete a set of ten short tasks. Participants completed tasks by interacting with a traditional and non-traditional vertical browser alignment. Left and right-handed participants were determined to be strikingly different in operation. Vertical scroll relocation produced some interesting results and responses.

Due to the common belief that language is unique to humans, great emphasis has been placed on the neocortex, while the role of the subcortical areas has been minimized. This project used event-related functional magnetic resonance imaging (fMRI) to study the linguistic involvement of the basal ganglia (BG). Previous research has demonstrated that the BG are implicated in building up sequences of behavior into meaningful, goal-directed repertoires This study developed the idea of motor sequencing into linguistic sequencing to test the BG's involvement in the abstract sequencing of language. Since past imaging studies failed to present a coherent picture of the BG laterality, which might be due to the absence of the control for subjects' familial handedness background, this subject factor was also investigated.Twenty-four right-handed, neurologically healthy English speakers were recruited. Half of them had left-handed blood relatives (FS+); the other half did not (FS-). Their tasks included 1) linguistic sequencing--reordering phrases into a sentence or reordering words along the general-specific dimension, 2) non-linguistic sequencing--swapping designated phrases/words and 3) repeat--repeating words in their original sequence. Voxel-wise analysis showed that both the BG and cortical areas were activated when subjects performed a reordering task. Region of interest (ROI) analysis demonstrated that the BG were involved in linguistic sequencing (reorder - repeat) and that Broca's area and the caudate head were co-opted in computing hierarchical structure (reorder - swap). Although familial sinistrality did not alter the activation pattern of Broca's area and the caudate head, it played a role in their activation asymmetry: both subject groups had left-lateralization in the inferior frontal gyrus, but they failed to show identical laterality in the BG. A possible explanation based on the direct and indirect pathways in the BG was offered and the laterality discrepancy was attributed to these two groups' different time course of language acquisition.To summarize, this study suggested that the BG, especially the head of the caudate nucleus, were involved in the abstract sequencing of language and that the distinct brain asymmetry associated with different familial sinistrality background might be rooted in the BG.

Tyrimo problema Mūsų visuomenėje neskiriama pakankamai dėmesio kairiarankiams, jų problemos yra ignoruojamos, apie ką kalbama ir užsienio autorių darbuose, tačiau iki šiol nėra pakankamai aiškios skirtingo abiejų žmonių rankų veiksnumo priežastys, sąsajos ir padariniai. Tyrimo tikslas. Ištirti, kaip priklauso dešiniarankiškumo/kairiarankiškumo laipsnis nuo fizinio aktyvumo lygio ir pobūdžio (t.y. ištirti dešiniarankiškumo ir kairiarankiškumo paplitimą tarp skirtingų sporto šakų atletų) ir nustatyti dešiniarankiškumo/kairiarankiškumo laipsnio sąsajas su rankų funkciniai ir anatominiais rodikliais. Darbo uždaviniai. 1. Anketavimo metodu nustatyti ir palyginti skirtingų sporto šakų atletų dešiniarankiškumo/kairiarankiškumo laipsnį. 2. Palyginti skirtingų sporto šakų atletų skirtingų rankų matmenų ir funkcinę asimetriją bei palyginti skirtingų sporto šakų ir grupių sportininkų rankų matmenų ir funkcinę asimetriją tarpusavyje. 3. Ištirti koreliacinę dešiniaranki���kumo/kairiarankiškumo laipsnio priklausomybę su rankų funkciniu ir matmenų asimetriškumu. Rezultatai. Iš visų tirtų 126 vyrų kairiarankių buvo 6,3 procento. Iš tirtų 33 kontrolinės grupės (nesportuojančiųjų) asmenų nė vieno pagal Bryden klausimyną nenustatėme esančio kairiarankiu. Tiek jėgos, tiek ištvermės sporto šakose buvo daugiau vyrų, kuriems dešinė ranka yra patogi rečiau/mažiau nei kairė (p<0,05). Tarp žaidėjų ir nesportuojančiųjų reikšmingas dešiniarankiškumo/kairiarankiškumo skirtumas nenustatytas (p>0,05)... [toliau žr. visą tekstą] / In the our days society, still not enough attention is paid at left-handed persons‘ problems, and we still lack the knowledge on the reasons and outcomes of the so-called hand preference, or handedness. Thus the aim of our study was to evaluate how the degree of handedness is dependent on the level and type of physical activity, and we studied three groups of athletes from different sports as well as sedentaries by standard questionnaire on hand preference as well as standard physical tests and anthropometry in order to determine the predilection of left/right-handedness among athletes from various different sports, and to obtain some better knowledge on the relationship of hand-preference with the functional and anthropometrical (a)symmetry of the hands. The results obtained revealed that among 126 of studied males 6.3 percent were clearly left-handed, but no one of the 33 control sedentaries was. Clear tendency was evident that among athletes of strength and endurance activities left-handedness was more expressed. This was not the case in ball-game athletes’ group. All groups when studies separately as well as one big group did not showed any signs of hand-size asymmetry, though some of the results of the tests for hand function were distinct between hands, the same in overall group and in four groups studied separately. These were handgrip strength, juggling with two baseballs, and maximal rate of hand and arm movements. The correlation between handedness score and... [to full text]

Since the face forms over the brain in the course of embryonic development, facial anthropometry may reflect brain structure. The motor functions of each side are controlled by the side of the brain opposite the body side. The purpose of this study was to establish whether a correlation exists between handedness and the location of the external auditory meatuses, as a possible consequence of brain asymmetry. Facial photographs were taken of 78 volunteers. Straws, placed in the external ear canals, were used to mark the external auditory meatuses. The level of the top of each meatus was measured from each volunteer's visual plane, as established by connecting the center of a point of reflected light in each pupil. Each volunteer was also given the Edinburgh Laterality Inventory (Durden-Smith and DeSimone, 1984:53) to determine "true" handedness (50 right-handers and 28 left-handers). Right-handers, as determined by either writing hand or laterality inventory, were found to exhibit a greater tendency for the left auditory meatus to be lower. Specifically, 68% of the right-handers, as opposed to 39% of the left-handers, exhibited a left external auditory meatus located at a lower position on the skull than the right meatus. This was significant at the 0.05 level. The differences in external auditory meatal distances from the visual plane were greater on the left in right-handers 68% of the time, equal 10%, and greater on the right 22% of the time. A reverse correlation for the right asymmetry for left-handers was not found. Instead, for the left-handed sample a nearly even distribution for meatal location was found: 39% left asymmetry, 29% symmetry, and 32% right asymmetry.The study strongly supported the hypothesis that right-handers have a significant tendency for left asymmetry in location of the external auditory meatuses. The study did not support the hypothesis that the meatal asymmetry correlates to the side opposite the handedness of the individual. Of-perhaps greater significance is the finding that the percentages of left asymmetry of both groups match the brain asymmetry percentages found by Galaburda (1984:15) for the planum temporale, an extension on the upper surface of the temporal lobe of the brain. The level of the external auditory meatuses, as a reflection of brain asymmetry, may serve as an external measurement of the location of Wernicke's area which is located near the planum temporale and has a major role in speaking and comprehension of the spoken word and in reading and writing. Simple techniques for locating the language centers of the brain would be an advantage in developing education plans and teaching strategies for students with each of the possible hemispheric dominance patterns. / Department of Anthropology

Thesis (Ph. D.)--University of Washington, 1990. / Vita. Includes bibliographical references (leaves [187]-208).