Full Episode
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are talking about time perception.
Our perception of time is perhaps the most important factor in how we gauge our life.
And the reason for that is that our perception of time is directly linked to the neurochemical states that control mood, stress, happiness, excitement, and of course, it frames the way in which we evaluate our past, it frames our present, whether or not we think we are on track or off track, and it frames our sense of the future. So let's talk about time perception.
And the most fundamental aspect of time perception is something called entrainment. Entrainment is the way in which your internal processes, your biology and your psychology are linked to some external thing. And the most basic form of entrainment that we are all a slave to all year round for our entire life are so-called circannual rhythms. We have neurons, nerve cells in our eye, in our brain,
and in our body that are marking off the passage of time throughout the year. Literally a calendar system in your brain and body. And the way this works is beautifully simple. Light seen by your eyes inhibits, meaning it reduces the amount of a hormone released in your brain called melatonin. Melatonin has two major functions.
One function is to make you sleepy at night, and the other is to regulate some of the other hormones of the body, in particular, testosterone and estrogen. Throughout the year, depending on where you live, day length varies. And as a consequence, the amount of light from the sun that is available to you varies.
So when days are long, the amount of melatonin in your brain and body that's released tends to be less. When days are very short, the amount of melatonin that's released and the duration that that melatonin exists in your brain and body tends to be much longer. So melatonin correlates with day length. And if we are viewing more light, we have less melatonin.
We view less light, we have more melatonin. You see different amounts of light each day, but we have a process in our brain and body that averages the amount of light that you're seeing both from artificial sources and from sunlight and measures that off.
And it's so exquisitely precise that for a given say eight hour day in the spring, because spring in the Northern hemisphere or elsewhere, you know, days are getting longer. That means that the amount of melatonin is getting progressively less and less, and that signal is conveyed to all the systems of your brain and body.
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