Tactile diagrams: worth ten thousand words?

The properties that make diagrams more effective than text in certain circumstances have been investigated by researchers for over 20 years. However, this research has focused on visual diagrams. To the best of our knowledge, no research has yet investigated whether the same benefits and properties hold for tactile diagrams, which are blind people's primary means of access to diagrams. We present a consideration of similarities and differences in the properties and potential benefits of visual and tactile diagrams; and suggest where experimental investigation would be useful.