Correlation versus causation in multisensory perception.

Events are often perceived in multiple modalities. The co-occurring proximal visual and auditory stimuli events are mostly also causally linked to the distal event, which makes it difficult to evaluate whether learned correlation or perceived causation guides binding in multisensory perception. Piano tones are an interesting exception: They are associated with the act of the pianist striking keys, an event that is visible to the perceiver, but directly results from hammers hitting strings, an event that typically is not visible to the perceiver. We examined the influence of seeing the hammer or the keystroke on auditory temporal order judgments (TOJs). Participants judged the temporal order of a dog bark and a piano tone, while seeing the piano stroke shifted temporally relative to its audio signal. Visual lead increased "piano-first" responses in auditory TOJ, but more so if the associated keystroke was visible than if the sound-producing hammer was visible, even though both were equally visually salient. This provides evidence for a learning account of audiovisual perception.