Why does caffeine not improve reaction time?

Caffeine can enhance alertness and focus, but it doesn't necessarily improve reaction time because the speed of a reaction depends on various factors, including neural processing speed and motor response. While caffeine may increase arousal and reduce fatigue, it doesn't directly accelerate the physiological processes involved in reaction times. Additionally, excessive caffeine can lead to jitteriness or anxiety, which may actually hinder performance. Thus, its effects on reaction time can be inconsistent and context-dependent.