Two experiments were conducted to determine if typical right hand target aiming advantages could be reduced or eliminated by increasing the spatial demands of the aiming task. In Experiment 1, we found right hand advantages for both movement time and error regardless of spatial characteristics of the task. When we introduced a greater degree of spatial uncertainty in Experiment 2, subjects exhibited a left hand reaction time advantage. Taken together our results suggest that the right cerebral hemisphere may have a special role to play in preparing the spatial aspects of an aiming movement, while the left hemisphere is more important for movement execution.Resume Deux experiences ont et6 effectuees afin de determiner si l'augmentation des demandes spatiales de la tache de visee pouvait reduire ou eliminer les avantages typiquement reli6s a la main droite lorsque celle-ci s'oriente vers une cible. Dans Pexperience 1, nous avons observe des avantages relies a la main droite pour ce qui est de la duree du mouvement et de la marge d'erreur, peu importe les caracteristiques spatiales de la tSche. Dans Fexp6rience 2 ou le degre d'incertitude spatiale etait plus 61eve, nous avons observe chez les sujets un avantage relie a la main gauche et au temps de reaction. Mis ensemble, les resultats laissent supposer que l'hemisphere cerdbral droit pourrait jouer un role particulier dans la preparation des aspects spatiaux des mouvements dirig6s vers une cible, tandis que I'h6misphere gauche serait plus important pour l'execution des mouvements.Asymmetries in the performance of various manual tasks are often attributed to the proficiency of the contralateral cerebral hemisphere for specific types of processing (Todor & Smiley, 1985). For example, right-hand advantages for finger sequencing (Edwards & Elliott, 1987) and rapid finger tapping (Todor, Kyprie, & Price, 1982) have been ascribed to left hemisphere specialization for the organization and control of sequential movement. Left side superiority for tasks involving tactile discrimination (Benton, Varney, &

No abstract

cardiac autonomic modulation during provocative stress show similar physiologic responses in young and older adults.

Graded decreases in RT may reflect a summation-mediated reduction in audiomotor transmission time, whereas step-like decreases associated with startle may reflect a bypassing of specific cortical circuits. We suggest that procedures presently used to start the Olympic sprint events afford runners closer to the starter the advantage of hearing the "go" signal louder; consequently, they react sooner but not more strongly than their competitors.

No abstract