Attention shifts that precede goal-directed eye and hand movements are regarded as markers of motor target selection. Whether effectors compete for a single, shared attentional resource during simultaneous eye-hand movements or whether attentional resources can be allocated independently towards multiple target locations is controversially debated. Independent, effector-specific target selection mechanisms underlying parallel allocation of visuospatial attention to saccade and reach targets would predict an increase of the overall attention capacity with the number of active effectors. We test this hypothesis in a modified Theory of Visual Attention (TVA; Bundesen, 1990) paradigm. Participants reported briefly presented letters during eye, hand, or combined eye-hand movement preparation to centrally cued locations. Modeling the data according to TVA allowed us to assess both the overall attention capacity and the deployment of visual attention to individual locations in the visual work space. In two experiments, we show that attention is predominantly allocated to the motor targets–without pronounced competition between effectors. The parallel benefits at eye and hand targets, however, have concomitant costs at non-motor locations, and the overall attention capacity does not increase by the simultaneous recruitment of both effector systems. Moreover, premotor shifts of attention dominate over voluntary deployment of processing resources, yielding severe impairments of voluntary attention allocation. We conclude that attention shifts to multiple effector targets without mutual competition given that sufficient processing resources can be withdrawn from movement-irrelevant locations.

目标定向的眼睛和手部运动之前的注意力转移被视为运动目标选择的标志。效应器是否会在同时进行的手眼运动中竞争单个共享的注意力资源，还是注意力资源是否可以独立分配给多个目标位置，一直存在争议。独立的，特定于效应器的目标选择机制是视觉空间对扫视和到达目标并行分配的基础，可以预测整体注意力能力随活动效应器数量的增加而增加。我们在修改后的视觉注意理论（TVA; Bundesen，1990）范式中验证了这一假设。参与者报告了在准备眼睛，手或组合的眼手动作过程中向中心提示位置简要介绍的字母。根据TVA对数据进行建模，使我们能够评估整体注意力能力和视觉注意力在视觉工作空间中各个位置的部署。在两个实验中，我们表明注意力主要集中在运动目标上，而效应器之间没有明显的竞争。但是，在眼部和手部目标上获得的并行效益在非运动场所会带来相应的成本，并且通过同时使用两个效应器系统，总注意力不会增加。此外，运动前注意转移在自愿分配处理资源方面占主导地位，严重损害了自愿注意分配。