Information capacity of the thumb and the index finger in communication.

Due to its large number of degrees of freedom and extensive connection to the brain, the human hand has been used to create channels of communication for a variety of human-machine systems. However, a fundamental question about the hand channel is still unanswered: what is its information capacity? This study aims to provide quantitative indication of effectiveness of the hand as a communication channel. We estimated that per gesture, the thumb and the index finger may deliver at most 10 and 7 bits of information, respectively. Based on this, we derived an upper bound for the information capacity of the hand in gesture-based communication: 150 b/s. Knowing this bound is critical to evaluating the potential and limitation of the hand channel for various forms of human-machine interactions.