Explain unfamiliar concepts in captions or surrounding text

Add brief explanatory text outside the marks when a chart uses concepts that some viewers may not know, especially when that concept is not central to the main message. For example, define uncertainty ranges or future scenarios in a caption, and explain a non-obvious baseline period or reference timeframe in nearby text.

Brief nearby explanations help viewers interpret unfamiliar concepts without forcing extra explanation into the visual itself. This reduces confusion about what a range, scenario, or reference period means before viewers infer the chart’s message.

Mechanism: Explanatory text gives readers a plain-language meaning for unfamiliar constructs, so they are less likely to read them as errors, unreliability, or arbitrary chart setup.

Evidence: Studies of chart interpretation found that some lay viewers misread or distrusted unexplained uncertainty ranges, practitioners often preferred explaining uncertainty in accompanying text when it needed extra explanation, and unexplained baselines or timeframes caused confusion that captions or surrounding text could reduce (Schuster et al., 2024; Schuster et al., 2023).

Notes: This guidance is most directly supported for cases where the unfamiliar concept supports the chart rather than being the chart’s main message.

• User Goal: Help viewers understand the chart’s intended message without getting stuck on a technical concept.
• Task: Interpret a chart that includes uncertainty, future scenarios, or a reference period.
• Data: The display includes a less familiar construct such as a shaded uncertainty range, a future scenario, or a baseline timeframe.
• Chart Setting: You can add a caption or surrounding text, and the concept does not need to dominate the visual itself.
• Audience: Viewers may have low domain knowledge or limited familiarity with the concept.
• Success Criterion: Viewers can explain what the concept means without treating it as unreliability or misunderstanding the timeframe.

Break it when: The unfamiliar concept itself is central to what viewers must read directly from the chart. Why: The source only supports moving explanation into accompanying text when that concept is not central, so nearby text alone may not carry enough of the message here.

Sacrifice: You use some caption or surrounding-text space. Risk: A vague explanation can still leave viewers unsure what the range or reference period means. Mitigation: Name the specific concept directly in the text instead of using a generic note.

Mistake: Showing an uncertainty range, future scenario, or reference period without any nearby explanation. Why it fails: Viewers may confuse it with unreliability or fail to understand the timeframe or baseline used in the chart.

Failure Sign: Reviewers ask what a shaded band, scenario label, or baseline period means. Quick Check: Scan the chart and caption for any unfamiliar range, scenario, or reference period that appears without a plain-language explanation nearby. Stronger Test: Ask a non-expert viewer to explain what that element means; if they hesitate, misstate it, or call it unreliable, the explanation is not clear enough.

• Add one caption sentence that states what the uncertainty range or scenario represents.
• Add a short nearby explanation for any baseline period or reference timeframe.
• Move that explanation into the caption or surrounding text instead of squeezing it into the visual when the concept is not central to the message.