Fastest artificially-assisted reaction times
Pedro Lopes, Jun Nishida, Shunichi Kasahara
0.05 second(s)
United States (Chicago)

The fastest artificially-assisted reaction time is 50 miliseconds from stimulus to action, which was achieved using electro-muscular stimulation (EMS) by researchers from the University of Chicago (USA) and Sony CSL (JPN). A typical human reaction time is about 250 ms. The results of the study, which was named Preemptive Action, were presented at the CHI 2019 conference in May 2019.

The Preemptive Action experiments involved fitting volunteers with a set of electrical muscle stimulators (EMS; adhesive pads designed to send a small jolt of electricity through the skin), which were wired up to a computerized control mechanism. They would be asked to attempt a task that required very fast reactions (such as catching a falling object or knocking a flying ball out of the air), first using their own reactions and then with the assistance of the EMS. The EMS was controlled by sensors that triggered instantaneously when the object was dropped or launched, sending a command that activated the muscles in just 50 ms.

When stimulated in this way, participants were acutely aware that their muscles had been activated by a external force. However, the researchers discovered that by delaying the EMS slightly – activating within 180 ms of the stimulus instead – they could give people superhuman reaction times without them losing the sense that they were controlling their own body. This is because around 200 ms of a typical human reaction time is the formation of intent, while only the last 50 ms is the time involved in activating the muscles. Sending commands before people are aware of their intent to move leads to an unsettling phenomenon that has been termed "possessed hand" by researchers in the field.