Specifically, the findings reveal that eye patterns center on a stranger's face if the viewer regards that person as a potential romantic love partner, whereas the viewer focuses more on the other person's body when the feeling is one of sexual desire. Though this may seem like an obvious progression, researchers say that automatic judgment can happen as quickly as half a second, producing contrasting gaze patterns.
The research team, from the University of Chicago, have published their results in the journal Psychological Science.
Lead author Stephanie Cacioppo, director of the High-Performance Electrical NeuroImaging Laboratory at the University of Chicago, says:
"Although little is currently known about the science of love at first sight or how people fall in love, these patterns of response provide the first clues regarding how automatic attentional processes, such as eye gaze, may differentiate feelings of love from feelings of desire toward strangers."
Through previous research, Cacioppo showed that love and sexual desire activate different networks of brain regions.
Results could have 'theoretical and clinical importance'
For this latest research, Cacioppo and colleagues from the University of Geneva in Switzerland had male and female university students view a series of black-and-white photos of strangers.
The study found that people focus their attention on a person's face when the viewer regards that person as a potential romantic love partner, versus the body for sexual desire.
In one experiment, the participants examined photos of young, adult heterosexual couples who were interacting with each other. Then, in another part of the study, the participants looked at photos of attractive people of the opposite sex who were looking directly at the camera.
None of these photos contained nudity or erotic images, note the researchers.
For both parts of the study, the participants sat in front of a computer and were asked to decide as quickly as possible whether the people in the photos drew out feelings of sexual desire or romantic love.
The time it took for the subjects to identify romantic love versus sexual desire did not differ significantly, which the researchers say shows that the brain can quickly process both emotions.
However, after analyzing the eye-tracking data, the researchers found that people tended to fixate their eyes on the face when the image evoked a feeling of romantic love, whereas when the images elicited sexual desire, the viewers' eyes moved from the face to focus on the rest of the body.
And this result was the same for both male and female participants.
"By identifying eye patterns that are specific to love-related stimuli, the study may contribute to the development of a biomarker that differentiates feelings of romantic love versus sexual desire," says John Cacioppo, co-author and director of the Center for Cognitive and Social Neuroscience.
The researchers conclude their study by noting how their findings could be put to use in practical applications:
"Such identification of distinct visual patterns for love and lust could have theoretical and clinical importance in couples therapy when these two phenomena are difficult to disentangle from one another on the basis of patients' self-reports."
In other similar research from earlier this year, Medical News Today reported on a study that suggested eye movement speed is linked to impulsive decision making.