What is dual coding and does it help learning?
Dual coding is combining words and visuals so that information is processed through two channels rather than one. It has reasonable evidence behind it and is frequently confused with the discredited idea of learning styles.
The underlying theory. Allan Paivio's dual coding theory proposes that we have separate systems for processing verbal and visual information, which can operate simultaneously. Presenting material through both creates two complementary representations and two routes to retrieval.
Richard Mayer's work on multimedia learning built on this, finding that people generally learn better from words and pictures together than from words alone — the multimedia effect.
Crucially, this is not learning styles. The learning styles claim is that individuals have a fixed preferred channel and should be taught through it, which has been tested repeatedly and not supported. Dual coding is the opposite claim: everyone benefits from both channels, because working memory has separate capacity for each and using both increases total capacity available.
What works in practice:
Diagrams and labelled illustrations alongside explanation.
Timelines, process flows and concept maps for sequences and relationships.
Drawing it yourself, which has stronger evidence than viewing someone else's — the drawing effect appears in several studies.
Dual-coded notes, combining text with sketches, which is one reason note-taking methods that reserve space for diagrams perform well.
The important caveats from Mayer's research:
Coherence. Decorative images unrelated to the content harm learning by consuming attention. Clip art is worse than nothing.
Redundancy. Narrating text that is also on screen word-for-word is worse than either alone, because it overloads the verbal channel.
Spatial contiguity. Labels should be adjacent to what they describe, not in a separate key.
Split attention hurts — requiring the learner to hold one element in mind while looking elsewhere.
Combine it with retrieval practice rather than using it as a substitute.