There's a mutual attraction between this guy in my doctoral program and me, and we have great conversations. I'd date him, but he's in a long-distance relationship. Recently, he started giving driving lessons to earn extra cash. I need to learn to drive a stick shift, so I signed up. This has morphed into our spending time together on weekends, having lunch, etc. My friends say this is a bad idea. But I guess I'm just following my heart. Is that so wrong to do?

--Crushing

"Follow your heart!" is like that "forget about money; do what you love!" professional advice. And go right ahead with that career in lentil sculpture -- assuming you're looking forward to spending your golden years in a very nice retirement tent.

As for all this time the guy is spending with you, consider that we seem to have evolved to have the romantic version of a spare tire in the trunk -- a "backup mate" (to the partner we're with). Evolutionary psychologists David Buss and Joshua Duntley explain that "mates might cheat, defect" (run off with another), "leave, or die. They might suddenly drop in mate value." Their research finds that both men and women seem to maintain backup mates -- three on average -- and "try to keep their backup mates out of other relationships" (like by giving them false hope during automotive lurchings around the parking lots of closed superstores).

You might also consider that there's more to making yourself attractive to a potential boyfriend than a few swipes of MAC and Maybelline. Social psychologist Robert Cialdini, reflecting on what he calls "the scarcity principle," points out that we value is what seems out of reach (as opposed to what's all over us like orange "cheese product" on a kid's veggies): "Study after study shows that items and opportunities are seen to be more valuable as they become less available."

In other words, until a man is girlfriend-free, it's in your best interest to be about as accessible to him as the upholstery of my late Grandma Pauline's couch was to the rumps of most of humanity. There were people she would remove the plastic covering for -- visiting movie stars and members of the British royal family (a la "I'm bored with St. Barts. How about a slushy January in suburban Detroit?").