sense of it all [Music] it seems easy enough to separate the sounds we hear from the sites we see but there is one illusion the reveals this isn't always the case have a look at this what do you hear ba ba ba bi yes ba ba ba ba but look what happens when we change the picture and yet the sound hasn't changed in every clip you are only ever hearing bar with a bee ah it's an illusion known as the McGurk effect take another look ba concentrate first on the right of the screen ah now to the left of the screen ba the