Text-dense pages show a horizontally decaying scanpath

What it is

A two-thousand-word help article: almost no cards, no hero, headings and paragraphs. Gaze heat often looks like this: the first paragraph is read well to the right; each later line is read less far; the left column is revisited; the right-hand middles and tails go nearly blank. That horizontally decaying scanpath is nicknamed an F-pattern. It describes sampling that has been observed on word-heavy, structure-poor pages. It is not a law of the web. Homepages, dashboards and tables do not take this shape. Forcing them into it invents a false problem.

Why it happens

In continuous reading, fixations walk the line and return to the next line’s start. Further down, readers shift from finishing lines to sampling them: just checking that the line is still the same topic. Horizontal span shortens and heat piles on the left. Headings in a help article offer a few docks, but paragraph interiors lack peaks that would pull gaze to mid-line or the end, so decay appears. It is a reading strategy plus missing lateral anchors, not an F-shaped template the visual system carries. A technical document with bold terms in every sentence grows second and third docks inside the line, and the F’s “bars” break.

Studying it

The material has to be long prose, not a card wall. Record fixation sequences, median horizontal span per line, and whether span falls with paragraph index; also report time in the left versus right thirds. Independent variables include genre (narrative, instructional, lists), inline emphasis, and measure. The dependent is the decay curve, not “does it look like an F.” Without an eye tracker, scroll and pointer traces are coarse proxies; a pointer is not gaze. Trying to replicate an F on a card-based marketing page is the wrong stimulus.

Where it stops holding

Left-to-right, horizontal type is the premise. In right-to-left scripts the decay sits on the right; vertical Chinese is a vertical sample, not a bar. The same reader in search mode (hunting an error code) jumps to keywords and the F vanishes. A first-screen image or a full-width button often takes the first landing, and only later body copy, if at all, enters decay. At most, then, the F is a descriptive statistic for “long prose, horizontal, browsing not searching.” It is not a layout prescription.

Applying it

• On long-prose UI, put the load-bearing clause at the paragraph start and on the start side. Do not leave exceptions, doses or prices only in the right half or at the sentence tail.
• When mid-line information must be read, plant docks: bold terms, inline code, short lists, so “further down, start-of-line only” is interrupted.
• Do not lay every home screen out as “important on the left, secondary on the right” because of an F you heard about. That copies a long-prose observation onto structured pages.
• Check: record a real reading (or eye track) on the target genre. Plot the rightmost position read on each line, by paragraph. If decay is clear, move any load-bearing fact that lives only in the decay zone to the paragraph start or onto its own short line. If decay is weak, do not redesign to make an F.

Related

• Same group: F3.04.2 Structured pages are scanned by jumping to visual weight · F3.04.3 Scan patterns change with reading direction and content type
• Nearby: F3.05 Visual flow · F3.09.1 The top and the start side are granted higher rank by default · F4.03 Line length
• Search terms: F-pattern · scanpath · reading saccade · text-heavy page