As a Sociology Major, I am always intrigued by the functional reasons underlying people’s behaviour. I found these quotes from Daniel Goleman’s book, Working With Emotional Intelligence particularly interesting:

“Emotions Are Contagious

All these abilities take advantage of a primal fact: We influence each other’s moods. Influencing another person’s emotional state for the better or worse is perfectly natural; we do it constantly, “catching” emotions from one another like some kind of social virus. This emotional exchange constitutes an invisible interpersonal economy, part of every human interaction, but is usually too subtle to notice.

[…]

In a primitive human band, emotional contagion – the spread from person to person of fear – presumably acted as an alarm signal, quickly focussing everyone’s attention on an imminent danger, like a stalking tiger.

Today, that same collective mechanism operates whenever word spreads of an alarming drop in sales, a coming wave of layoffs, or a new threat from a competitor. Each person in the chain of communication activates the same underlying emotional state in the next, and so passes on the message to be alert.

[…]

The emotional economy is the sum total of the exchanges of feeling among us. In subtle (or not so subtle) ways, we all make each other feel a bit better (or a lot worse) as part of any contact we have; every encounter can be weighted along a scale from emotionally toxic or nourishing. While its operation is largely invisible, this economy can have immense benefits for a business or for the tone of organizational life.”