Opposites attract, but only sometimes: study

Dr. Helen Fisher, a biological anthropologist, suggests that the answer lies in your brain chemistry, LiveScience reports. She discussed her research recently at the Being Human conference in New Jersey.

For that feel-good romantic feeling and sexual drive, we can thank brain chemicals such as dopamine and testosterone, she said. But a specific balance of chemicals shapes our personalities and affects the type of people we are drawn to romantically, the report said. Some of us like people who are more like us. For others, opposites attract.

LiveScience reports that Fisher scoured scientific literature to determine the brain chemicals associated with certain physiological traits and then formulated a personality assessment to determine which combination of chemicals is dominant in a given person. She administered the test to 28,000 people on a dating website and then watched to see whom they selected in their matches.

Findings showed that people with "active dopamine systems tended to be reward-driven and impulsive, seeking out novelty and experience and getting bored easily," LiveScience writes. They also "tended to be curious, energetic, and mentally flexible, but not particularly introspective." "They like their own type," Fisher said.

Serotonin also plays a role and is linked with personality types that are less anxious and more social. These types also tend to be more conscientious, religious, and drawn to people more like themselves.

But those with testosterone-dominant personalities -- often highly analytical and competitive -- tended to be drawn to people with personalities associated with high estrogen and oxytocin levels, who are more nurturing and introspective, the report said. The effect worked both ways, with the estrogen/oxytocin group being drawn to people who were more testosterone dominant.