A picture is worth a thousand words—or is it?

Stephan Lewandowsky

A picture is worth a thousand words—or is it?

How does a pulley work? What about a block and tackle? According to Wikipedia, “A pulley is a wheel on an axle that is designed to support movement and change of direction of a cable or belt along its circumference.” When multiple pulleys are combined together “so that they rotate independently on the same axle [they] form a block. Two blocks with a rope attached to one of the blocks and threaded through the two sets of pulleys form a block and tackle.”

Easy? Perhaps, but somehow I would prefer to see something like the figure below (also from Wikipedia), which tells me that the load required to lift weight W is now 1/3 of what it would be if one were to lift W directly.

Diagrams surely often simplify explanations, and statistical graphs have a long history of being superior to tabular representations in some circumstances.

So are pictures, diagrams, and graphs always worth the proverbial 1,000 words?

In a recent article in the Psychonomic Society’s journal Memory and Cognition, researchers Ortegren, Serra, and England argued that diagrams are not always worth 1,000 words—sometimes they may only be worth 1 repetition.

Ortegren and colleagues pitted a well-known cognitive fact against the proposition that diagrams confer a unique advantage on cognition. It is a fact that repetition of information helps memory. Sometimes it helps more than at other times, but we can at least expect a small benefit on memory by repeating information. So if a diagram accompanies a text, then arguably the diagram repeats the information. Perhaps the diagram aids comprehension or recall by mere repetition, rather than by some intrinsic pictorial attribute?

To test this idea, Ortegren and colleagues conducted two experiments that simultaneously examined the two variables of interest: Whether or not the information was repeated and whether or not diagrams were present. Thus the studies included a condition in which the diagrams were presented on their own (as was the text in a comparable textual condition); a condition in which the text was repeated by further text; plus the conventional condition in which the diagrams accompanied (and thereby repeated) the text.

Ortegren and colleagues argued that “if diagrams aid recall simply because they repeat text-based information, then any repetition of the information—including text-based repetitions—should produce similar effects on recall for that information.” The figure below contrasts that hypothesis (in the top left) with other possible outcomes. According to a visual hypothesis, the diagrams would always win and repetition would not matter (top right); according to an additive hypothesis the two modes of presentation would assist each other (bottom left); and the multi-modal hypothesis would argue that a diagram is worth a 1,000 words, but only if it is accompanying text.

The results turned out to be remarkably similar across their two studies: When people had to freely recall the information (i.e., without any prompts or cues other than “explain to me how lightning storms develop” after reading a passage on lightning), the only thing that mattered was repetition. People recalled the information better when it was shown a second time, but it didn’t matter whether the repetition involved a diagram or further text.

The results were different for “cued recall’, that is, when memory was tested by providing specific prompts (one for each of the diagrams or equivalent textual passages presented). For example, people might be asked “Why does lightning appear to flicker?” after studying a paragraph about lightning. The answer, by the way, is shown in the diagram below:

Lighting involves multiple so-called “dart leaders” that carry negative charges from the cloud down to the surface, and that are followed by return strokes. This process can occur anywhere up to 20 times or more during a lighting, which can give it its flickering appearance.

I trust you found the above diagram helpful, because with cued recall, Ortegren and colleagues found support for the additive hypothesis: Providing a diagram, rather than text, enhanced memory performance, and that boost was further increased by repetition of the information.

The combined take-home message is fairly straightforward: If you want someone to remember something, repeat the information. And in many situations, a diagram adds more than just a repetition to memory—it may not always be worth 1,000 words but, even at a few hundred words, a diagram still packs quite a bit of punch.

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