Narrowing of the audio-visual temporal binding window due to perceptual training is specific to high visual intensity stimuli

The temporal binding window (TBW), which reflects the range of temporal offsets in which audio-visual stimuli are combined to form a singular percept, can be reduced through training. Our research aimed to investigate whether training-induced reductions in TBW size transfer across stimulus intensities.
32 observers performed simultaneity judgements at two visual intensities with a fixed auditory intensity, before and after receiving audio-visual TBW training at just one of these two intensities.
We show that training individuals with a high visual intensity reduces the size of the TBW for bright stimuli, but this improvement did not transfer to dim stimuli. The reduction in TBW can be explained by shifts in decision criteria. Those trained with the dim visual stimuli, however, showed no reduction in TBW.
Our main finding that perceptual improvements following training are specific for high-intensity stimuli, potentially highlighting limitations of proposed TBW training procedures.