Have you ever tried to hear a fellow diner talking in a noisy restaurant and noticed that you were watching their lips to try and understand what they were saying?
Your brain often combines sensory clues to work out what’s going on.
In a noisy restaurant for example, you often combine two senses (hearing and vision) to work out what’s being said (language processing).
Usually, this works out well. Sometimes, it doesn’t work out so well, as you’ll discover if you try this test and see what other people think they heard too.
Watch the video and listen to what the person is saying.
If you think (like most people) that you heard “da-da” while watching the video, you experienced the McGurk-MacDonald Effect.
If you don’t believe us, play the video again, but close your eyes to check whether you can hear “da-da” or “ba-ba”.
Sometimes, what you hear can be affected by what you see, but usually when we watch someone speaking, the sounds they make match their lip movements.
For this test however, the woman’s mouth was filmed saying "ga-ga" but the video was accompanied by a "ba-ba" soundtrack.
When the two sensory signals differ (like seeing “ga-ga” lip movements but hearing “ba-ba”), your brain fuses the signals together as best as it can and assumes you’re hearing “da-da”.
The McGurk-MacDonald Effect only works for certain phonemes including “ba-ga” and “pa-ka”, (which you hear as “ta”). When the effect occurs for these phonemes, sensory information is combined or integrated preconsciously before language processing occurs in your brain.