When presented with written data, audiences will read. They can’t help themselves. This is due to complex neural issues of having to make sense of images. Whilst a picture can be examined at the same time as listening, this is what you do by simply having your eyes open, interpretation of text requires engagement of a further part of the brain at the same time. This requires increased concentration particularly if some idiot is talking in the background.
Something I like to do to highlight this issue is to present a slide full of text whilst talking, then “hide” the slide and watch all the faces turn to look at me. Then “unhide” the text again and watch the faces as one turn to look back to the slide. And repeat. This tennis spectator movement is fun two or three times but proves the point. Audiences are hypnotised, like a chicken, by what is written on the screen.
(no chickens were harmed in the production of this blog post)