Don’t fill slides with additional information.

Viewers have about ten to twenty seconds to take everything in, while also listening to what you are saying.

Compare the two videos below. The first has a slide with too much (additional) information on it; it doesn’t reflect exactly what the speaker is saying. It’s confusing reading one thing and listening to the speaker saying another thing, all at the same time.

The slide in the second video is more streamlined and echoes exactly what is being said.