Simon and Garner effects with color and location: Evidence for two independent routes by which irrelevant location influences performance

Classic theories of attention assume that the processing of a target’s featural dimension (e.g., color) is contingent on the processing of its spatial location. The present study challenges this maxim. Three experiments evaluated the dimensional independence of spatial location and color using a combined Simon (Simon & Rudell Journal of Applied Psychology: 51, 300−304, 1967) and Garner (Garner, 1974) design. The results showed that when the stimulus’s spatial location was rendered more discriminable than its color (Experiment 1 and 2), both Simon and Garner effects were obtained, and location interfered with color judgments to a larger extent than color intruded on location. However, when baseline discriminabilities of location and color were matched (Experiment 3), no Garner interference was obtained from location to color, yet Simon effects still emerged, proving resilient to manipulations of discriminability. Further correlational and distributional analyses showed that Garner and Simon effects have dissociable effects. A triple-route model is proposed to account for the results, according to which irrelevant location can influence performance via two independent location routes/codes.