If you’re single and looking to change that status, perhaps you have been pondering the mysteries of romantic attraction. It will come as no surprise to learn that research has established that physical appearance is one factor that predicts attraction. This is starkly evident in online dating. A study of thirty-somethings found that being rated in the top (versus bottom) ten percent on physical attractiveness roughly tripled the probability of receiving a “first-contact” message (Hi! How are you?). Like it or not, looks matter in the dating game.  

But do not despair if you don’t have movie-star good looks. Intelligence predicts attraction, too—and not only in humans, it turns out. In a study just published in Science, a team of scientists in China and the Netherlands showed that female parakeets showed greater preference for males that they observed demonstrating problem-solving skill. This finding provides the most direct support to date for the evolutionary hypothesis, first advanced by Charles Darwin himself, that mate selection is one way that human intelligence has evolved.

At the beginning of the experiment, male and female parakeets (also known as budgerigars) were randomly assigned to either a problem-solving group or a control group. In both groups, the birds were tested in a specially designed cage in triads consisting of a “focal” female and two “demonstrator” males. The cage was divided into three compartments by transparent screens: a main compartment, where the female was placed, and side compartments, where the males were placed. The female had perches in the middle of her compartment (the “neutral zone”) and on either end (the “preference zones”). Over four days of observation, the male near which she spent more of her time was identified as the “preferred” male and the other one as the “less-preferred” male.

Next, the birds were taken out of the testing cage. In the problem-solving group, over the course of a week, the less-preferred male was given training in two “puzzle box” tasks in which the goal was to access birdseed. The first puzzle box required the bird to open a petri dish; the second one required him to open the lid to the box, pull open a door, and pull out a drawer. (The preferred male received no training.) All three birds were then put back into the testing cage for an “observing phase” in which both males attempted to open the puzzle boxes in view of the female. In the control group, the focal female simply observed the less-preferred male eating out of a regular food dish. Finally, the scientists once again measured the female’s preference for the males.

The results supported Darwin’s hypothesis. In the problem-solving group, the females’ preferences shifted. Most of the females now preferred the skilled (and previously less-preferred) male, all but ignoring the unskilled (and previously preferred) male. (Intelligence was, to borrow from the psychologist Timothy Leary, the “ultimate aphrodisiac” for these lady birds.) By contrast, in the control group, the females’ preferences were unchanged. This finding indicates that it was the demonstration of problem-solving skill related to foraging, and not mere access to food, that caused females’ preferences to shift. As a follow-up, the researchers repeated the experiment with all female birds. There was no preference shift to the skilled female. Thus, the key result was specific to males and was presumably driven by mate selection.

Humans are obviously more complex creatures than parakeets, but mate selection may be a factor in the evolution of human intelligence, as well. Intelligence predicts people’s ability to survive and thrive in their environments. Smart people tend to live long, healthy, productive lives. Consequently, we may have evolved to become attracted to people whose behavior signals high intelligence. For the single among us, there’s practical message here for dating: make yourself look nice, but don’t forget about the intelligent conversation.