They aren't common, but enormously interesting. How can it be that you've been together that long and you're still intensely in love with them?

The basic issue about being too close is being closer than you're comfortable with.

Our findings show that the brain areas activated when someone looks at a photo of their beloved only partially overlap with the brain regions associated with sexual arousal. Sex and romantic love involve quite different brain systems.

Four minutes of eye contact brings people closer to each other better than everything else.

The basic issue about being too close is being closer than you're comfortable with. For some people, even slightly close is too much and for other people being enormously close is great.

There's this general craving-and-desire system that's engaged, only in this case the desire isn't for money or a drug or power or freedom. The desire is for merging with another person.