WASHINGTON (AP) -- Puzzling new research suggests women have a harder time than men looking at babies with facial birth defects.

It's a surprise finding. Psychiatrists from the Harvard-affiliated McLean Hospital, who were studying perceptions of beauty, had expected women to spend more time than men cooing over pictures of extra-cute babies. Nope.

Instead, the small study being published Wednesday raises more questions than it can answer.

First the background: The McLean team already had studied men and women looking at photos of adults' faces on a computer screen. They rated facial beauty, and could do various keystrokes to watch the photos longer. A keystroke count showed men put three times more effort into watching beautiful women as women put into watching handsome men.

Lead researcher Dr. Igor Elman wondered what else might motivate women. Enter the new baby study.

This time 13 men and 14 women were shown 80 photos of babies, 30 of whom had abnormal facial features such as a cleft palate, Down syndrome or crossed eyes. Participants rated each baby's attractiveness on a scale of zero to 100, and used keystrokes to make the photo stay on the screen longer or disappear faster.

Women pressed the keys 2.5 times more than men to make photos of babies with the facial abnormalities disappear, researchers reported in PLoS One, a journal of the Public Library of Science. That's even though they rated those babies no less attractive than the men had.

"They had this subliminal motivation to get rid of the faces," said Elman, who questions whether "we're designed by nature to invest all the resources into healthy-looking kids."

Both genders spent equal time and effort looking at photos of the normal babies.

The study couldn't explain the gender disparity. Elman noted that previous work has linked child abandonment and neglect to abnormal appearance, and even asked if the finding might challenge the concept of unconditional maternal love.

That's too far-reaching a conclusion, cautioned Dr. Steven Grant of the National Institute on Drug Abuse, which funded the study.

The work is part of broader research into how we normally form attachments and what can make those attachments go awry, work that tests if what people say matches what they do.

"Common sense would tell you one thing," Grant said. "This doesn't fit with common sense. It raises a question."

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