The present study extended recent research revealing that illusions can influence performance in golf putting (Witt, Linkenauger, & Proffitt Psychological Science, 23, 397-399, 2012), by exploring the potential mediating roles of attention and action planning. Glover and Dixon's (Journal of Experimental Psychology. Human Perception and Performance, 27, 560-572, 2001) planning-control model suggests that both perceptual and movement-planning processes are prone to illusion-based bias. We therefore predicted that both the perception of target size and a measure of attentional control related to movement planning in golf putting (the quiet eye) would be influenced by the illusion. Moreover, as performance could not be corrected using online control (once the ball was struck), we predicted that these biases would also influence performance. We therefore proposed a three-stage process by which illusory context biases perceptual processes, which in turn bias subsequent attentional control related to movement planning, which in turn biases motor performance. Forty novice golfers completed an Ebbinghaus illusion putting task that was designed to manipulate their perceptions of target size, while quiet eye duration and performance (mean radial error) were measured. The results indicated that the illusion was effective in facilitating differences in perceived target size, with perceptually bigger holes promoting longer quiet eye durations and more accurate putting. Follow-up mediation analyses revealed that illusion-based differences in size perception partially mediated illusion-based differences in both quiet eye duration and performance. Moreover, the relationship between illusion-based differences in quiet eye duration and performance was also significant. Future research should further test this three-stage process of bias in other far-aiming tasks in which online control cannot be used.Keywords Titchener circles . Quiet eye . Size perception . Movement planning . Online control Illusions provide an interesting means to examine the larger issue of how the central nervous system codes and uses visual information for different types of cognitive and motor tasks (Mendoza, Hansen, Glazebrook, Keetch, & Elliott, 2005). Recently, Witt and colleagues explored the impact of an illusory visual context on golf-putting performance (Witt, Linkenhauger, & Proffitt, 2012). Specifically, an Ebbinghaus illusion around the target hole (see Fig. 1) was effective at inducing significant differences in perceptions of target size and in subsequent putting performance: Participants holed significantly more putts when they were putting to a perceptually bigger hole. The aim of the present study was to elucidate potential mechanisms underpinning the illusion effect shown by Witt et al., using Glover and Dixon's (2001) planning-control model as a theoretical framework. We hoped that such research might help further our understanding of how perceptual and attentional processes mediate performance variability in far-aiming tasks like...