Back in the 1 870 s，Charles Darwin’s cousin Francis Gahon wanted to define the face of a criminal．He assembled photographs of men convicted of heinous crimes and made a composite by lining them up on a single photographic plae The surprise：everybody liked the villain，including Gahonhimself．He reasoned that the villainous irregularities he supposed belonged to criminal faces had disappeared in the averaging process．In the next century，scientists began to show reliably thatfaces combined digitally on computers were likable--more so than the individual faces from which they were composed Although people clearly admire the long legs of Brazilian model Ana Hickmann or Dolly Parton’s breasts，in general humans like averages． Researchers confirmed that humans judge real faces by their differences or similarities from anorm．But they also found that the norm can change quickly．When researchers showed 1 64 peoplesets of 100 computer—generated faces representing a slow transition from male to female and from Japanese to Caucasian--it turned out that the test subjects’idea of what constitute an“average”face shifted depending on the first face they saw．When they were flashed a supermasculine face first，more faces on the spectrum impressed them，by contrast，as female The masculine face had，in effect，set a standard From then on，other faces had to be more masculine in order to rate as be longing to the gender．the study note a similar shift using a Scale of faces moving from surprise to 1‘disgust． The authors，who published their results in the journal Nature，conclude that in real life we al so quickly change our perception of the midpoint--what’s normal--depending on what we see We may not be aware that our judgment has changed；we simply see differently，says Michael Wel)ster，a psychologist at the University of Nevada in Reno and coauthor of the study． One implication is that individual and social attitudes toward what’s acceptable，and what’s beautiful，change over time “If you look at plastic—surgery trends”，in the 1950s and 1960s you saw little upturned noses，notes Harvard psychologist Nancy Etcoff，author of the book Survival of the Prettiest：The Science of beauty．“Now the noses are broader and the lips are plumper．We’re seeing images from around the globe and its changing our idea of the average”So if you’re unhappy with some aspect of your face，take comfort：beauty，is a moving target．
Francis Gahon’s test shows that________．

A. people prefer average faces to those with conspicuous features
B. sometimes evil persons have more attractive appearance
C. it is hard to distinguish between criminals and ordinary people
D. the result of trying to read faces is a shock to average people