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If a guy offers to carry a box for a female co-worker, help her with Google Analytics or compliments her for what a good mom she seems to be, she may be better off turning down the help and deflecting the compliments. These seemingly nice gestures and complimentary comments towards women may be a form of subtle sexism, experts say.

Chivalrous acts and compliments on female qualities, like mothering or nurturing, studies show, can be just as damaging to women as more blatant sexism and catcalls. Offering to assist women in traditionally male tasks, which experts call benevolent sexism, reinforces the notion that men are more competent than women, and women are weak and fragile.

One study found that when women were led to expect help from men, they became unsure of themselves, got distracted, and consequently performed poorly, creating a self-fulfilling prophesy. Women don’t usually recognize benevolent sexism, and they start to doubt their ability to do the job, which makes them less able to do the job, the study’s co-author Peter Glick said in a podcast.

“In benevolent sexism, you can genuinely cherish someone in the workplace, but you can help her too much,” said Glick, professor of psychology at Lawrence University in Appleton, Wis.  “It’s subjectively positive, but it’s bad for the woman."

The rate of benevolent sexism in the country correlates with how well women are doing at work, in education, and in health care, reported Glick and his co-author Susan Fiske, who is professor of psychology at Princeton.

New commentary, in which they cite their research, was in Psychology of Women Quarterly.

“Benevolent sexism is part of a system of control of women and does correlate with objective indicators of how well women were doing in the nation,” she said.

Moreover, benevolent sexism tends to justify hostile sexism.

“Scratch a benevolent sexist and you might find a hostile sexist underneath,” Glick said. Hostile sexism is the more blatant type of aggression and negative stereotyping of women.

Just how common is subtle sexism in the workplace?  Researchers from Pennsylvania State University and Philipps University in Marburg, Germany, conducted three studies asking 120 participants (82 women and 38 men ranging in age from 18 to 26) to keep diaries of a list of subtle sexist comments and actions for seven days. Participants observed an average of six sexist incidents during the week.

Researchers found when women were made aware of subtle sexism and how to spot it, they no longer had self doubts and their performance didn’t suffer.

Men, though appear to be slower at getting the message and had to be more actively educated that any kind of sexism harms women.

Laurie Tarkan is an award-winning health journalist whose work appears in the New York Times, among other national magazines and websites. She has authored several health books, including "Perfect Hormone Balance for Fertility." Follow her on Twitter and Facebook.