Why do we fall in love? Speed-dating zebra finches offer clues.

Pairing off is an expensive process, and not just because the price of red roses spikes around Valentine's Day. Humans idealize an enchanted meeting, romantic courtship, and happily ever after. Rarely do lovers think about the impact that their blind dates, summer flings, and friend zones could have on the species.

Researchers have wondered why the sticky process of "falling in love" has been allowed to continue. While most animals streamline courtship practices, humans keep updating their dating profiles without regard for evolutionary fitness.

Researchers with the Max Planck Institute for Ornithology in Germany have offered a few answers in an article published Monday by the online journal PLOS Biology. Researchers Malika Ihle, Bart Kempenaers, and Wolfgang Forstmeier used zebra finches, a species of bird that – like humans – chooses mates based on characteristics known only to themselves, mate for life, and raise their children together. 

"Here, one original point of the study is to focus only on this 'idiosyncrasy' in mate preference, i.e. on individual-specific preferences," Dr. Ihle told The Monitor. 

Their experiment involved 160 birds, who were chosen in groups of 20 males and 20 females for a "speed-dating" exercise. In the wild, the males would perform their courtship song to a smaller and smaller group of females, then pairs build a nest.

The researchers made one key change. According to a PLOS press release, "Once the birds had paired off, half of the couples were allowed to go off into a life of wedded bliss. For the other half, however, the authors intervened like overbearing Victorian parents, splitting up the happy pair, and forcibly pairing them with other broken-hearted individuals."

The study concluded that self-chosen birds had successful families at a 37 percent higher rate than the arranged couples. The birds who stayed with their mate of choice produced fewer unhatched eggs and healthier chicks. 

Moreover, the females appeared less interested in romance with an arranged partner, and the males in these pairs wanted less to do with newly hatched chicks. In the randomly arranged pairs, the males especially were prone to philandering in other nests. 

The human application – if there is one – is about choosing a partner who will pull his or her own weight when the children arrive. 

"Is it a matter of personality matching, synchronisation/coordination of activities, or a matter of stimulation/motivation by your partner in investing all the work it takes to raise a family, as our exploratory analyses tend to suggest?" Ihle asked. 

The innovative part of this experiment was the focus on behavioral compatibility, the fact that finches stuck in a "loveless marriage" were obviously less interested in each other, and it affected the chicks negatively. Ihle said the study suggests it is a matter of motivation, with each partner being willing to help out with the kids, but this could be more definitively tested with a twin study. She said she would next like to see a study that measures how one couple's behavioral compatibility can truly be better than another's.