The “Flash-Lag” Effect Occurs in Audition and Cross-Modally

In 1958 MacKay showed that a rigidly moving object becomes visually fragmented when part of it is continuously visible but the rest is illuminated intermittently. For example, the glowing tip of a lit cigarette moving under stroboscopic illumination appeared to move ahead of the intermittently lit body. Latterly rediscovered as "the flash-lag effect" (FLE), this illusion now is typically demonstrated on a computer monitor showing two spots of light, one translating across the screen and another briefly flashed in vertical alignment with it. Despite being physically aligned, the brief flash is seen to lag behind the moving spot. This effect has recently motivated much fruitful research, prompting a variety of potential explanations, including those based on motion extrapolation, differential latency, attention, postdiction, and temporal integration (for review, see ). With no consensus on which theory is most plausible, we have broadened the scope of enquiry to include audition and have found that the FLE is not confined to vision. Whether the auditory motion stimulus is a frequency sweep or a translating sound source, briefly presented auditory stimuli lag behind auditory movement. In addition, when we used spatial motion, we found that the FLE can occur cross-modally. Together, these findings challenge several FLE theories and point to a discrepancy between internal brain timing and external stimulus timing.