Think about the last time you swiped through a dating app or stood at a diner counter trying to choose between the burger and the salad. You probably found yourself looking back at one of them before you knew you'd made a choice. That’s no coincidence, according to the study, ‘Gaze bias both reflects and influences preference,’ published in the journal Nature Neuroscience by Caltech scientist Shinsuke Shimojo and colleagues. The 2003 study, with eye-tracking equipment, showed that gaze reliably shifts towards whatever option a person is about to select in the final seconds before the decision.
What the researchers actually did
In the study, researchers recorded eye movements while small groups of participants viewed pairs of human faces and selected which one they found more attractive, taking as long as they wanted before pressing a key to record their choice. No one spoke, and no response was required until the decision was final; the only thing that was measured was where each person's eyes lingered.
At the beginning of a trial, attention was distributed approximately equally between the two faces. But the study found that as the seconds passed, gaze was increasingly biased in the direction of whichever face the person ultimately chose. And in the toughest comparisons, when the two faces were rated equally attractive, that gaze bias was as high as 83% in the moments preceding the decision. They called this the gaze cascade effect because the bias grew over time, like a snowball rolling downhill, rather than staying flat.
