Study participants assessed cars based on a system known as geometric morphometrics (GM), which allowed the men and women to rate certain traits on a sliding scale (such as "infancy" to "adulthood"). The traits represented maturity, sex, attitudes, emotions, and personality — all things that people infer from human faces at a single glance.
After rating car traits, participants then answered the question of whether they saw a human face, animal face or no face at all on the cars. They drew facial features such as eyes, nose and mouth on the car images whenever they did see faces.
Lastly, the study participants answered whether they liked a car or not. The study restricted car choices to passenger cars, because hulking SUVs would have skewed the results.
People overwhelmingly preferred cars that rated highest on "power" traits." High "power" cars like the BMW 5 Series tended to be lower or wider, and have slit-like or angled headlights with a wider air intake.
Link -Thanks, Geekazoid!