#3 BBC 6 minutes English listening - When do you feel sleepy

In this article, I'd like to summarize a listening practice article from http://www.bbc.co.uk/learningenglish/chinese/features/6-minute-english/ep-161215.

When do you feel sleepy?

Episode 161215 / 15 Dec 2016

This episode is talking about when do people feel like to sleep in a biological way.  

The reason is circadian rhythms, which means the rhythms of how day and night changes.  By this factor, we can know that human’s sleeping behavior is related to the changes of the light.  Due to this reason, blind people and some shift workers has different endogenous clocks than others.   

In addition, exercise, food, and caffeine, may also has some influence on circadian timing, but not as strongly as the light-dark cycle.