Long-term training reduces the responses to the sound-induced flash illusion.

The sound-induced flash illusion (SiFI) is a robust auditory-dominated multisensory integration phenomenon that is used as a reliable indicator to assess multisensory integration. Previous studies have indicated that the SiFI effect is correlated with perceptual sensitivity. However, to date, there is no consensus regarding how it corresponds to sensitivity with long-term training. The present study adopted the classic SiFI paradigm with feedback training to investigate the effect of a week of long-term training on the SiFI effect. Both the training group and control group completed a pretest and a posttest before and after the perceptual training; however, only the training group was required to complete 7-day behavioral training. The results showed that (1) long-term training could reduce the response of fission and fusion illusions by improving perceptual sensitivity and that (2) there was a "plateau effect" that emerged during the training stage, which tended to stabilize by the fifth day. These findings demonstrated that the SiFI effect could be modified with long-term training by ameliorating perceptual sensitivity, especially in terms of the fission illusion. Therefore, the present study supplements perceptual training in SiFI domains and provides evidence that the SiFI could be used as an assessment intervention to improve the efficiency of multisensory integration.