40. Multiple Sensory Channels Compete

Imagine that you are driving while listening to the radio and talking to a passenger sitting next to you. You are processing multiple sensory channels simultaneously. You are watching (the road), listening (to the radio and your friend), and thinking and talking. This doesn’t sound too difficult. People process multiple sensory channels all the time. But there is a limit. The more channels you try to process at the same time, the trickier multichannel processing becomes. If one of the channels becomes complicated or difficult to process, then processing more than one channel can get very challenging. For example, what if there is a sudden storm while you are driving, and torrential rain makes it hard to see the road? It will start to get hard to pay attention to, or remember, what your friend is saying.

Listening and Reading Don’t Mix Well

During a presentation, there are two sensory channels that are most active: visual and auditory. Your audience might be looking at you while also looking at your slides. They are also listening to what you’re saying. If the slides are visuals that are easy to understand—such as photos, or diagrams that add extra context and meaning to the presentation—then the multiple channels are a positive experience for them. But if, instead, the slides are hard to read or complicated, then your audience will be distracted.

In particular, the sensory combination of slides that are filled with text and a speaker who is talking is simply a bad combination. In order to understand the slides, your audience has to read. As soon as they are reading, they are not listening. Listening and reading are two sensory channels that compete with each other. Figure 40.1 shows an example of a slide with just brief summary text. Figure 40.2 is a version of the slide that requires too much reading.

Figure 40.1. Less to read

Figure 40.2. Too much for people to read