The McGurk effect

[pne]

Have a look at, and listen to, this video; the video is someone pronouncing one sound, while the audio is the person pronouncing another sound, and apparently most people hear something that's a blend of the two—showing that the visual influences your perception. (For comparison, close your eyes and listen again, and you'll likely hear what he said.)

FWIW, I "heard" a retroflex sound rather than the dental/alveolar that the page predicted! But certainly, it was a type of "d" to me.