Humans are the only creatures on Earth that shed tears. Whether it's tears of joy, laughter, anger, pain, sadness, or fatigue, the emotions that bring about crying are diverse. You might be familiar with these emotional triggers, but have you ever wondered about the physiological explanations behind them?

Let's start by categorising tears into three types. There are "basal" tears that maintain a continuous lubrication of the cornea, "reflex" tears that emerge when you're chopping onions, have dust in your eye, or encounter too much light, and then there are the emotional tears – and they’re the ones we're delving into today.

What happens in our eyes when we're sad? What about tears of joy then? But why does witnessing someone else cry make us want to do the same?

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A podcast written and realised by Joseph Chance.

In partnership with upday UK.

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