Social scientists think race is a misleading concept. ??? ??? ??? reaction time The time it takes to respond to a stimulus, either physically (with a reflexive movement such as an eyeblink) or cognitively (with a thought). ??? ??? ??? reactive aggression An impulsive retaliation for another person's intentional or accidental action, verbal or physical. ??? ??? ??? reflex An unlearned, involuntary