Humans are attracted to those who they feel they can understand the emotions of, scientists have discovered. Using brain scans and experiments relating to emotion and attractiveness, a team from the Universität zu Lübeck in Germany say they have potentially found a neural basis of human relationships.

Being able to understand another person's emotional state is important for social interactions. Humans need to be able to discern between a hostile, sad or happy person in order to react appropriately.

When it comes to romantic partners, this is all the more important. A couple must be able to anticipate the other person's behaviour and adapt their own accordingly. In a study published in the journal PNAS, researchers say evolutionary theory would expect we would tend to select people whose behaviour and communication signals are easy for them to decode. However, the brain functions relating to interpersonal attraction and selection are not yet well understood.

To investigate, researchers asked male and female volunteers to view video clips of a woman expressing either fear or sadness. The volunteers' brain activity was measured through MRI. After each clip, they were asked to say if the woman felt fear or sadness and then rated how confident they were about each answer. How much they were attracted to each picture was assessed through self-reporting and the option of increasing the size of each picture.

Reward centre of brain

Researchers found that the more certain the participant was about a woman's emotional state, the more attracted they were towards her. Higher confidence and attraction were also found to be associated with increased activity in the area of the brain relating to reward.

"The greater the match, the larger the brain's intrinsic reward signal," the researchers wrote. "Taken together, these findings provide evidence that reward-related neural activity during social encounters signals how well an individual's 'neural vocabulary' is suited to infer another person's affective state, and that this intrinsic reward might be a source of changes in interpersonal attraction."

They said the findings indicate mutual understanding "is an important factor in interpersonal attraction" and further research into the common neural vocabulary of suitors will provide a better understanding of the neurobiological factors influencing social relationships.