A deafening flash! Visual interference of auditory signal detection

- Some people claim to hear what they see: a visually-evoked auditory response (V-EAR).
- We assess the prevalence and perceptual reality of V-EAR for the first time.
- 22% of subjects confirmed they heard faint sounds accompanying silent visual flashes.
- V-EAR is perceptually real enough to interfere with detection of real sounds.
- V-EAR may be a normally-occurring precursor to visual-to-auditory synaesthesia.

In some people, visual stimulation evokes auditory sensations. How prevalent and how perceptually real is this? 22% of our neurotypical adult participants responded 'Yes' when asked whether they heard faint sounds accompanying flash stimuli, and showed significantly better ability to discriminate visual 'Morse-code' sequences. This benefit might arise from an ability to recode visual signals as sounds, thus taking advantage of superior temporal acuity of audition. In support of this, those who showed better visual relative to auditory sequence discrimination also had poorer auditory detection in the presence of uninformative visual flashes, though this was independent of awareness of visually-evoked sounds. Thus a visually-evoked auditory representation may occur subliminally and disrupt detection of real auditory signals. The frequent natural correlation between visual and auditory stimuli might explain the surprising prevalence of this phenomenon. Overall, our results suggest that learned correspondences between strongly correlated modalities may provide a precursor for some synaesthetic abilities.