What dual coding is
Your brain has partly separate channels for verbal and visual information. Encode a concept through both and you have two independent routes to retrieve it later — if the words fail you, the picture might not. That redundancy is the whole mechanism, and it is why a well-labelled diagram is worth a great deal more than either the diagram or the label alone.
Why 'learning styles' is a different claim, and a false one
The learning-styles claim is not that pictures help. It is that *matching* teaching to a student's preferred style improves their results — that a 'visual learner' learns more from a diagram than a 'verbal learner' does. When that specific prediction is tested, it fails. People have preferences; those preferences do not predict what they learn best from.
The practical damage is real: a student who has decided they are 'visual' avoids reading, which in most degrees is the material. You are not a visual learner. You are a person, and people remember things better with pictures attached.
Doing it properly
- Draw it yourself. A diagram you generate is worth far more than one you look at — looking at somebody else's is passive.
- Label everything, in words. A picture without language is half a code.
- Then reproduce it from memory, blank page, no source. This is the step that converts it from art into studying.
- Use images where the image is the content — anatomy, circuits, phase diagrams, timelines, anything spatial.
- Don't decorate. A pretty, irrelevant image next to a paragraph competes for attention rather than reinforcing it.