The speaker is the source of information not the visual aids

In any kind of instruction, visual aids add to the message, but they should not be the message.

The focus of the teaching, influence or persuasion should be the speaker or teacher, not the medium
Powerpoint slides do not by themselves do a good job of transmitting information.
A talk with just someone reading a series of slides is very boring.
sometimes effects on visual aids may take the concentration of the main point and detract from the teaching.

"It’s primarily the group that produces, that brings out meaning. It’s not arrows, diagrams, circles, triangles. The tool sends you back to a question—where is the focus, on the speaker or the medium?—whether it involves teaching, influence, or persuasion. Is it the tool? Is it the speaker? If the speaker takes the central position, the tool can be used well. If the central place is left to the tool, it will seize it and the speaker will no longer be aware that the tool is managing the meeting. If the tool is in the center, the speaker is sending a clear message: he is letting the tool do the job. You measure the consequences when you’re on the other side of the stage. On the pretext of being sure to transmit the message, a manager makes you swallow a series of slides. He reassures himself and you think he’s hiding behind the tool. Managers see very clearly how the mistake happens. Once the tool contains the information, people think displaying it is all you need to do to transmit "