The effect of the Müller-Lyer illusion on saccades is modulated by spatial predictability and saccadic latency

Abstract

Studies investigating the effect of visual illusions on saccadic eye movements have provided a wide variety of results. In this study, we test three factors that might explain this variability: the spatial predictability of the stimulus, the duration of the stimulus and the latency of the saccades. Participants made a saccade from one end of a Müller-Lyer figure to the other end. By changing the spatial predictability of the stimulus, we find that the illusion has a clear effect on saccades (16%) when the stimulus is at a highly predictable location. Even stronger effects of the illusion are found when the stimulus location becomes more unpredictable (19–23%). Conversely, manipulating the duration of the stimulus fails to reveal a clear difference in illusion effect. Finally, by computing the illusion effect for different saccadic latencies, we find a maximum illusion effect (about 30%) for very short latencies, which decreases by 7% with every 100 ms latency increase. We conclude that spatial predictability of the stimulus and saccadic latency influences the effect of the Müller-Lyer illusion on saccades.

Susceptibility to Optical Illusions Varies as a Function of the Autism-Spectrum Quotient but not in Ways Predicted by Local–Global Biases

“…This could have influenced the results. We know that eye movements have a strong influence on susceptibility to the Müller-Lyer illusion (e.g., de Grave & Bruno, 2010;van Zoest & Hunt, 2011) and that people with and without ASD differ in the way they scan visual scenes (Pelphrey et al, 2002). It then follows that perhaps the effects on the Müller-Lyer illusion observed by Chouinard et al (2013) Walter et al (2009) argued that greater levels of systemising meant a greater focus on details, which in turn reduced abilities in global integration and levels of susceptibility to some of their illusions.…”

Is Mislocalization during Saccades Related to the Position of the Saccade Target within the Image or to the Gaze Position at the End of the Saccade?

“…There is ample evidence that when we make a saccade from one endpoint of the shaft of a Müller-Lyer figure to the other, our eyes land further from the starting point for the fins-out configuration of the figure (>–<) than for the fins-in configuration of the figure (<–>) for the same length of the shaft [18]–[23]. The reason for this is that information about the distance that is to be moved is used to plan saccades [24]–[26], so since the misjudged distance between the two endpoints of the Müller-Lyer figure is used to plan the saccade, the illusion influences the saccade amplitude [27].…”

Fooling the Eyes: The Influence of a Sound-Induced Visual Motion Illusion on Eye Movements

“…Thus, the pattern of results found here might not hold for other sensory-motor systems such as those that subserve hand-related actions. Regarding the question of whether the oculo-motor effects found here are based entirely on attention shifts, it is notable that previous studies have shown reduced effects of visual illusions on saccade amplitudes with full attention [17]. In a study of Muller-Lyer illusion [17], it was reported that illusion effects on eye movement were largest for fast compared to longer saccadic latencies.…”

“…Regarding the question of whether the oculo-motor effects found here are based entirely on attention shifts, it is notable that previous studies have shown reduced effects of visual illusions on saccade amplitudes with full attention [17]. In a study of Muller-Lyer illusion [17], it was reported that illusion effects on eye movement were largest for fast compared to longer saccadic latencies. Longer latencies result in a smaller illusion, suggesting that with sufficient time the oculomotor system was able to determine an accurate position of the target.…”

“…In this case, the experimental paradigm can influence whether the illusion influences saccadic landing positions or not. It has been shown that the effect of the Muller-Lyer illusion on eye movements is modulated by saccadic latency [17], with longer latency saccades being less influenced by the visual illusion than shorter latency saccades. Moreover, the predictability of target stimuli modulated the effects of the ML on eye movement amplitude, with a stronger illusion effect for unpredictable stimuli locations [17].…”