Men and women make mating decisions very differently, he speculates.

Men tend to act like single-issue voters: If a prospect is not attractive enough, he or she usually doesn’t qualify for a first date, period.

Most people end up with someone who’s about as good-looking as they are.“People might prefer attractive people, but they often end up pairing off with people who are similar in attractiveness,” Leslie Zebrowitz, a psychology professor at Brandeis University and an expert on face perception, said.

“You might shoot for the moon, but you take what you can get.”Twenty years ago, Christina Bloom was in a committed relationship when she met someone who “knocked me off my heels.” The two embarked on a fiery romance, during which she noticed that friends and strangers were always telling them they looked alike.

As one columnist who used the service put it, “There’s a short bio, age, and mutual friends listed, but who’s really paying attention to that stuff when your Tinder flame is wearing next to nothing on the beach?

”Then there’s Hinge, which uses a similar interface, but is backed by recommendations from the user’s “social graph,” such as their school or career field.

Here, then, is how to date online like a social scientist.

Tinder offers a one-sentence tagline and a selection of five photos, including the all-important first photo, or “calling card,” as the writer Amanda Lewis put it.

She launched Face Mate in 2011, drawing on her opinion that people in happy relationships tend to resemble each other.

The site matches the photos of its users based on their faces’ bone structure using face-scanning techniques and a computer algorithm.

This trait game, along with Royzman’s review of the literature on attraction, hints at some of the endless quirks of the online dating marketplace.

You might like someone online, but they put 100 on income, and unfortunately you’re about a 10.

Grindr serves up a mosaic of gay bachelors’ head and body shots.