When visual attention is divided in the flash-lag effect

Abstract

The flash-lag effect (FLE) is the perceived lagging behind of a flash physically aligned to a continuously moving object. The illusion is attributed to a compensatory mechanism of motion extrapolation, which ensures that the perceived position of a moving object aligns with its real- time position despite neural processing delays. While several studies have demonstrated that attention can modulate the FLE, the precise role of attention in the extrapolation process remains elusive. Thus, in the current study, we sought to disentangle the influence of visual attention by manipulating the amount of attention allocated to moving stimuli in different locations. By directing attention to one, two, three, or four stimuli presented in different quadrants across trials, we measured the trial-wise FLE to investigate potential FLE magnitude or variability modulations under different attention conditions. Our results showed that FLE magnitudes were significantly larger when attention was divided among two, three, or four stimuli than when attention was focused on one stimulus. Surprisingly, FLE variability showed no difference across attention conditions. These findings show that the compensatory mechanisms for neural processing delays in dynamic environments are modulated by attention to enable efficient processing of multiple objects simultaneously.