The farther a legend sits from the chart, the more every lookup costs the reader's eye

What it is

The farther the legend sits from the graphic, the more every matching round-trip costs: the gaze travels a longer path and re-focuses more often. Distance does not merely slow each lookup — it has a second-order consequence: when the legend is too far, readers give up on the trip altogether and guess the category from impression, upgrading the failure from "slow" to "wrong."

Why it happens

The round-trip cost has two components: the saccade itself (longer distances take longer) and the fixation switch (re-focusing at the landing point, rebuilding context). Both rise monotonically with legend-to-chart distance. The more critical factor is working-memory decay: the colour feature the reader memorised at the mark must still be usable on arrival at the legend — the longer the trip and the more interference along the way, the more the feature decays and the lower the comparison accuracy. Distance therefore taxes two things at once: speed and accuracy.

Where it stops holding

Interactive hover lets readers obtain the category name in place, bypassing the distance cost — at the price of an extra action that resolves one point at a time. On small screens the legend usually sits close to the plot, so distance cost is naturally low, though space compression introduces its own occlusion problems. The rule matters most for static charts and print — where distance is fixed and no interaction exists, legend distance is a pure cost variable.

Applying it

• Place the legend inside or adjacent to the plot area (an empty corner, near the line ends); never in a far canvas corner or the page footer.
• Measure the visual distance from legend to marks during layout review: shrink it wherever possible — legend size yields to distance.
• Verification: screen-record readers matching categories; a travel path visibly longer than the chart itself means the legend is too far — move it in.

Related

• Same group: U5.02.2 Legend arrangement direction should match the graphic's spatial order · U5.02.3 Above, right, and below placements carry different matching costs · U5.02.4 Too many legend entries degrade matching into a linear search · U5.02.5 Interactive legends double as filters, but clickability must be signalled
• Nearby: U5.01.1 Legends force eye round-trips between chart and key · U5.01.2 Direct labelling eliminates the round-trip
• Search terms: legend proximity · gaze transition cost · legend placement