  Chord diagrams are widely used for visualizing data connectivity and flow
between nodes in a network. They are effective for representing complex
structures through an intuitive and visually appealing circular layout. While
previous work has focused on improving aesthetics and interactivity, the
influence of fundamental design elements on user perception and information
retrieval remains under-explored. In this study, we explored the three primary
components of chord diagram anatomy, namely the nodes, circular outline, and
arc connections, in three sequential experiment phases. In phase one, we
conducted a controlled experiment (N=90) to find the perceptually and
information optimized node widths (narrow, medium, wide) and quantities (low,
medium, high). This optimal set of node width and quantity sets the foundation
for subsequent evaluations and were kept fixed for consistency. In phase two of
the study, we conducted an expert design review for identifying the optimal
radial tick marks and color gradients. Then in phase three, we evaluated the
perceptual and information retrieval performance of the design choices in a
controlled experiment (N=24) by comparing four chord diagram designs (baseline,
radial tick marks, arc color gradients, both tick marks and color gradients).
Results indicated that node width and quantity significantly affected users'
information retrieval performance and subjective ratings, whereas the presence
of tick marks predominantly influenced subjective experiences. Based on these
findings, we discuss the design implications of these visual elements and offer
guidance and recommendations for optimizing chord diagram designs in network
visualization tasks.
