Kissing releases masses of oxytocin, a "love potion" that helps couples bond and feel more attracted to each other.
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Two in five people in the world marry their first love.
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40% of people who are rejected in romantic love slip into clinical depression.
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Parents receive 1 out of every 5 Valentines.
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When dragonflies mate, their tails form a love heart.
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Falling in love raises levels of nerve growth in a person's brain for about a year and can improve their memory.
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Every year around 1 billion Valentine cards are sent. After Christmas it's a single largest seasonal card-sending occasion.
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