Does apparent size capture attention in visual search? Evidence from the Muller-Lyer illusion

Is perceived size a crucial factor for the bottom-up guidance of attention? Here, a visual search experiment was used to examine whether an irrelevantly longer object can capture attention when participants were to detect a vertical target item. The longer object was created by an apparent size manipulation, the Muller-Lyer illusion; however, all objects contained the same number of pixels. The vertical target was detected more efficiently when it was also perceived as the longer item that was defined by apparent size. Further analysis revealed that the longer Muller-Lyer object received a greater degree of attentional priority than published results for other features such as retinal size, luminance contrast, and the abrupt onset of a new object. The present experiment has demonstrated for the first time that apparent size can capture attention and, thus, provide bottom-up guidance on the basis of perceived salience.