I agree with previous posts that the contiguity principle is a bit hard to understand, but David’s example makes it clearer, thank you. @david, maybe one of the reason for violating the multimedia principle is that it can often be hard and time-consuming to find useful images? Also, I feel like it depends quite a lot on the discipline as Georgina says. Some disciplines probably lend themselves to images more than others.
I also struggle a bit with the signalling principle and how this works in practice – I guess it means using lots of diagrams with arrows to show the relationships between concepts?