First, Chasserot took a series of portrait photos of each participant. Then, the photos were edited, feature by feature, to create new portraits that agreed with or defied accepted western beauty standards. While hooked up to a brain-activity monitor, participants were then shown each of the new photos. When each participant's brain reading hit a particular threshold of "engagement," this was noted as a silent preference for that particular face.
To get those readings, Chasserot used electroencephalography (EEG) measured by the Emotiv tool. This can track the timing and strength of different types of brain waves, which are then associated with different activities and states. Although we don't know exactly what the engagement reading is measuring, the activity has been described as a combination of concentration and attention, and some have suggested it's related to working memory. Also, EEG signals have been used before as markers of personal significance and preference, so this isn't that far of a stretch. But, Chasserot tells us he considers this just a pilot study; he's looking for a psychologist to collaborate with on future endeavors.
When the original photos were placed next to the idealized versions, the results were striking. Some participants clearly preferred their faces with dramatically larger eyes and more defined cheekbones, while others' ideal faces were almost replicas of their real-life portraits.