Having another person help you with a simple physical task often seems to be more trouble than it's worth. In such dyadic tasks each person's limb motion responds to the output of the other's motor control system as well as his own, which might well be expected to complicate motor planning and efficient task execution.
To investigate kinesthetic (also called haptic) dyadic interaction, we set up a target acquisition experiment in which two subjects moved opposite ends of a rigid two-handled crank. Many subjects found their partner to be an annoyance, but they completed the tasks faster than either subject could when working individually. Furthermore, dyads tended to adopt a specialization of roles which must have been negotiated through this channel of communication, since there was no other.
Many other kinds of pair interaction have been heavily studied, including facial expression, gesture, spoken language, and visually observing each other's actions. Kinesthetic interaction has been little studied; I'll describe the most related prior work, which was done in 1956. I speculate that haptic interaction is a form of human communication that may be used to develop a cooperative strategy for motor tasks requiring coordination with another person.
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