Fitts' Law for speed-accuracy trade-off is a diversity sweet spot in sensorimotor control

Abstract

Human sensorimotor control exhibits remarkable speed and accuracy, as celebrated in Fitts' law for reaching. Much less studied is how this is possible despite being implemented by neurons and muscle components with severe speed-accuracy tradeoffs (SATs). Here we develop a theory that connects the SATs at the system and hardware levels, and use it to explain Fitts' law for reaching and related laws. These results show that diversity between hardware components can be exploited to achieve both fast and accurate control performance using slow or inaccurate hardware. Such “diversity sweet spots'' (DSSs) are ubiquitous in biology and technology, and explain why large heterogeneities exist in biological and technical components and how both engineers and natural selection routinely evolve fast and accurate systems from imperfect hardware.