That the preference for the average is biological rather than cultural has been supported by studies on babies, who gaze longer at attractive faces than at unattractive ones. Furthermore, Mark Stauss reported that 10-month-old children respond to average faces in the same way as they respond to attractive faces, and that these infants can extract the average from simply drawn faces consisting of only 4 features. Adam Rubenstein and coworkers showed that already at six months of age, children not only treat average faces the same as they treat attractive faces, but they are also able to extract the central tendency (i.e. the average) from a set of complex, naturalistic faces presented to them (i.e. not just the very simple 4-features faces used by Strauss). Thus the ability to extract the average from a set of realistic facial images operates from an early age, and is therefore almost certainly instinctive.