Determinants of right-left and top-bottom prevalence for two-dimensional spatial compatibility

When stimulus and response sets vary along horizontal and vertical dimensio ns, the horizontal dimension is more dominant than the vertical one, an eff ect called right-left prevalence. Three accounts have been proposed that at tribute the effect to a reduced ability to code vertical locations when hor izontal codes are also present, the use of right-left effectors, or a diffe rence in salience of the 2 dimensions. The accounts differ in terms of whet her the ability to code and process the 2 dimensions is of limited capacity and whether the prevalence effect is a consequence of the effectors used f or responding. The authors report 4 experiments that evaluated these issues . Results indicate that use of right-left effectors is important to the rig ht-left prevalence effect because it increases the salience of the horizont al dimension, However, a top-bottom prevalence effect can be obtained if th e vertical dimension is made more salient.