Makes the concept map easier to read and interpret

Parents

Helps to identify and distinguish a thought type from other types and tie type to its related tags. May supersede colors associated with type.
Indicates that the thought is an organizational container and not a member of a schema / semantic structure
Reinforces visual distinction between tags
Visually distinguishes tags from each other and aligns sets of tags with sets of types for easy correlation
Visually identifies thought type and distinguishes from other types. This enables pattern recognition and visual filtering.
Visually reinforces type and may contain additional information.