When it came to buckling up, pretty and ugly children were treated in starkly different ways, with seat belt use increasing in direct proportion to attractiveness. When a woman was in charge, 4 percent of the homeliest children were strapped in compared with 13.3 percent of the most attractive children. The difference was even more acute when fathers led the shopping expedition -- in those cases, none of the least attractive children were secured with seat belts, while 12.5 percent of the prettiest children were.

Homely children were also more often out of sight of their parents, and they were more often allowed to wander more than 10 feet away.

Age -- of parent and child -- also played a role. Younger adults were more likely to buckle their children into the seat, and younger children were more often buckled in. Older adults, in contrast, were inclined to let children wander out of sight and more likely to allow them to engage in physically dangerous activities.

Although the researchers were unsure why, good-looking boys were usually kept in closer proximity to the adults taking care of them than were pretty girls. The researchers speculated that girls might be considered more competent and better able to act independently than boys of the same age. The researchers made more than 400 observations of child-parent interactions in 14 supermarkets.

Dr. W. Andrew Harrell, executive director of the Population Research Laboratory at the University of Alberta and the leader of the research team, sees an evolutionary reason for the findings: pretty children, he says, represent the best genetic legacy, and therefore they get more care.