The purpose of this thesis was to investigate manual asymmetries in the reach-to-grasp movement based on two hypotheses: 1) manual asymmetries are resultant from asymmetries in the dorsal vision-for-action system; and 2) manual asymmetries are contingent on task difficulty. Participants grasped glasses of water under different visual-feedback conditions. Demand was manipulated by varying the level of the water contained in the glass. Hand asymmetries of the reach-to-grasp movement were studied through kinematic analyses. Visual feedback availability and task demand affected all kinematic measures. Manual asymmetries were found in peak velocity, movement time, and variability of maximum grip aperture. Consistent with reach-to-point literature, reach-to-grasp actions were faster and more accurate when performed with the right hand and when guided by the dorsal vision-for-action system. The results of the thesis provide support for a theory of left-hemisphere specialization for the visual control of actions. / xiv, 121 leaves : ill. ; 29 cm

M.A. (Psychology) / Research investigating the connection between Functional Hemispherical Asymmetry (FHA) and perception of affect in clinical as well as normal populations, is characterised by contradictory findings with regard to the role of the different hemispheres, especially as regards the perception of various valencies of emotions. Although a majority of studies indicates that the right hemisphere (RH) is superior in the perception of all valencies and emotions - positive as well as negative - there are numerous studies indicating a possible differential processing of positive and negative emotions by the hemispheres. Although various researchers try to lay the above contradictory findings and the general lack of consensus at the door of methodological problems/inequalities or error variances, the literature is increasingly pointing to the existence of evidently reliable individual differences between people as regards their hemispherical functioning. The problem investigated in the current study, is to determine the possible role of the organismic variables in FHA, i e variables seated in the individual who is making the observation. In this study, the focus is specifically on the role of sex and the temperament dimension of introversion-extraversion. The objectives of this study are to determine whether there are significant differences in the direction of these hemispherical differences, as well as the relative performance, of groups divided according to sex and temperament characteristics, and whether the relevant organismic variables offer a possible means of explaining the contradictions in research results on FHA and the perception of emotion. In this study, the measuring of FHA is operationalised in terms of the differential performance, measured in terms of accuracy and speed of observation (response latency) of the hemispheres in the perception of different valencies of emotional stimuli (positive versus negative, and approach versus avoidance emotions).. The subject population comprised a group of students selected in terms of sex and temperament (introversion-extraversion). Selection in terms of introversion-extraversion was done on the basis of subjects' performance in the Personality Questionnaire Form B (Schepers, 1991): persons falling in the lower and upper three stanines of the scale respectively were identified as introverts and extraverts. Only right-handed subjects with no history of brain injury were used for the study. Differential hemispherical performance in terms of response accuracy and latency was determined by means of the Divided Visual Field Technique (DVFT). Although the reliability data of this technique are generally not entirely satisfactory when measured in terms of psychometric test standards, an effort was made to enhance the reliability of the technique in this study by controlling specific stimulus and response variables (inter alia the exposure time and the use of both hands for a response) during the experimental design.