Data from two experiments investigating the impact of handedness and effector strength on a compatibility effect between physical stimulus size and left/right responses

Humans respond more quickly with the left hand to a small stimulus, and with the right hand to a large stimulus, as compared to the reverse mapping (SSARC effect). We investigated the hypothesis that strength differences between the hands contribute to the origin of this effect. Therefore, 80 left-handers and 80 right-handers participated in two experiments. In Experiment 1, participants performed a manual choice-response task where we manipulated the mapping between physical stimulus size and response hand. In addition, we measured the strengths of participants’ left and right effectors (i.e., finger, hand, arm). In Experiment 2, we measured the SSARC effect in vocal responses in the same sample. There were four main results. First, participants’ dominant effectors were stronger than their non-dominant effectors. Second, the SSARC effect occurred in manual and vocal responses with similar size. Third, in both modalities, the SSARC effect was larger in right-handers than in left-handers. Finally, strength differences between effectors (fingers, hands) correlated with the size of the SSARC effect. In sum, results support the hypothesis that functional differences between the hands contribute to the origin of the SSARC effect. In addition, the results suggest that multiple size-space assocations may exist in parallel, or that space-size associations have generalized across motor systems, and formed a modality-independent association.与反向映射相比，人类对小尺寸刺激会以左手做出更快反应，对大尺寸刺激则以右手做出更快反应，该现象即为大小-刺激-反应相容性效应（Size-Stimulus-Response Compatibility effect，SSARC）。本研究旨在验证“双手力量差异是该效应产生的根源”这一假说。为此，共招募80名左利手者与80名右利手者参与两项实验。实验1中，参与者完成一项手动选择反应任务，我们在此任务中操控物理刺激尺寸与反应手之间的映射关系。此外，我们还测量了参与者左右侧效应器（即手指、手部、手臂）的力量水平。实验2中，我们在同一批被试样本中，通过语音反应测量了SSARC效应。本研究共得到四项核心结果：其一，参与者的优势侧效应器力量显著强于非优势侧效应器；其二，手动反应与语音反应中均出现了SSARC效应，且二者的效应量相近；其三，在两种反应模态下，右利手者的SSARC效应量均大于左利手者；最后，效应器（手指、手部）间的力量差异与SSARC效应的大小呈显著相关。综上，本研究结果支持“双手功能差异是SSARC效应产生的根源”这一假说。此外，本研究结果还提示，大脑中可能并行存在多种大小-空间关联，或是空间-大小关联已在多个运动系统间实现泛化，进而形成了一种不依赖反应模态的跨模态关联。