Happy accidents — coincidences — are among the more joyful phenomena out there. Take this one, for example. Girl is photographed while taking a photo. Boy posts aforementioned photo on Flickr, which girl stumbles upon, also being a Flickr member. Boy and girl meet and start dating and are still dating two years later.

These sorts of coincidences happen every day, and yet they give us a soaring sense of joy, even when they’re happening to someone else. I think this is because of the phenomenon of improbability, which makes unlikely events seem meaningful. Coincidences are actually statistically more likely than we would guess them to be, a gap between belief and reality which leads to many opportunities for wonder and joy. Our desire for our world to have meaning and for our own lives to be special trumps our brain’s ability to calculate accurately, one of many examples where emotion trumps reason in the way we perceive the world.

Witnessing a happy coincidence in someone else’s life gives us hope for that same random, unlikely joy in our own lives. It is a case where joy comes not from the memory of a prior pleasurable event but from the hope and anticipation of a future one. As the many comments for the photo attest, people are uplifted by the narrative, and it brings out warm feelings.

Of course, not all coincidences are happy ones. Dick Cavett recently wrote in the New York Times about a particularly horrifying one. But with the grace of an irrepressible optimism, we seem more able to chalk these negative coincidences up to chance. Perhaps this means we’re wired to seek and find joy, whatever the odds?