Interpretations of graphs seem to be rooted in principles of cognitive naturalness and
information processing rather than arbitrary correspondences. These predict that
people should more readily associate bars with discrete comparisons between data
points because bars are discrete entities and facilitate point estimates. They should
more readily associate lines with trends because lines connect discrete entities and
directly represent slope. The predictions were supported in three experiments, two
examining comprehension and one production. The correspondence does not seem to
depend on explicit knowledge of rules. It may reflect the influence of the
communicative situation as well as the perceptual properties of graphs.