The research record and the practice record are kept apart, as in every topic (method). For figures, the best evidence is mostly about charts and interfaces.
Best evidence
Sub-question
Record holder
Measured how
Q11a Layout
Purchase 1997; Huang 2008b
experiments on comprehension of graph drawings; path tracing against crossing angle
Q11a Layout, the map of the field
Burch 2021
survey of 239 papers of user studies of graph visualisation
Q11b Visual channels for quantities
Cleveland 1984; Heer 2010
perception experiments, and their crowdsourced replication
Q11b Grouping
Palmer 1992
laboratory demonstrations of grouping by common region
Q11c Appeal and performance
Thielsch 2019; Schlamann 2026
meta-analyses, 25 and 31 studies, for interfaces
Q11c Embellishment
Bateman 2010; Borgo 2012
controlled experiments on charts, description and recall
Q11d Reaching a figure without sight
W3C 2023e; W3C 2023a
a standard; not tested with readers
Q11d Reading by a language model
Zhong 2024
500 random graphs, text against image, one model
Q11e Practice
none
no study of a style guide's rules was found
Most adopted
Practice
Holder
Sign of adoption
Ten rules for better figures
Rougier 2014
the reference most practice pages cite
A stated message, direct labels, little decoration