Human: What are the effects of caffeine? Assistant: 
The effects of caffeine vary from person to person, but in general, it can increase alertness, improve mood, improve focus and concentration, reduce feelings of fatigue, and increase energy levels. It may also have a positive effect on physical performance, appetite, and digestion. However, too much caffeine can lead to side effects such as anxiety, restlessness, insomnia, tremors, and rapid heartbeat.