  In this paper, we explore the effectiveness of tactile data encodings using
swell paper in comparison to visual encodings displayed with SVGs for data
perception tasks. By replicating and adapting Cleveland and McGill's graphical
perception study for the tactile modality, we establish a novel tactile
encoding hierarchy. In a study with 12 university students, we found that
participants perceived visual encodings more accurately when comparing values,
judging their ratios with lower cognitive load, and better self-evaluated
performance than tactile encodings. However, tactile encodings differed from
their visual counterparts in terms of how accurately values could be decoded
from them. This suggests that data physicalizations will require different
design guidance than that developed for visual encodings. By providing
empirical evidence for the perceptual accuracy of tactile encodings, our work
contributes to foundational research on forms of data representation that
prioritize tactile perception such as tactile graphics.
