Abbreviated Reaction Time

Reaction time, in its basic definition, is the amount of time it takes to respond to a stimulus.

Abbreviated reaction time (also known as reduced reaction time or central reaction time) as defined in 1868 by the Dutch ophthalmologist Franciscus Cornelius Donders (1818–89), is "the fraction of reaction time that remains after subtracting the time taken up by the passage of a nerve impulse from the sensory receptor to the brain and for another nerve impulse from the brain to the muscle."

Simply put, this is the reaction time minus the few fractions of a second that it takes for the body to send a message to the brain and then receive the physical answer such as the amount of time involved in touching a hot stove and pulling your hand away.