A person's tendency to be a night owl, early bird or some place in between is known as their chronotype. Depending on their chronotype, people are likely to be more awake and alert during certain times of the day and sleepier during others. Genetics play a big part in whether you're a lark or an owl, but the environment also has a role. "People tend to participate in daily activities that reinforce their chronotype," added Ms Drerup. "For example, night owls feel more productive and alert at night, so they tend to exercise and socialize in the evening. These activities are stimulating and reinforce the person’s tendency to stay up late"