10 Things Your Boss Won't Tell You-II

4. "Your kid? Your problem."

By now it's common knowledge that women earn less than men about 81 cents for every dollar. Having a kid hurts women's earning potential even further. The so-called "mommy penalty" may manifest in many ways: A mother may get passed over for a promotion because the boss thinks she takes off too much time to care for her kids or that she's more concerned about the family than her career. A mom may get overlooked for high-profile projects because the boss fears she won't devote enough time and energy.

Those are hard slights to quantify. Not so for the penalty faced by women who take time off to raise a child even for a period as short as 18 months. Women with M.B.A.s who left the workforce for a year and a half to raise children make 41% less than men with the same degree; female Ph.D.'s make a third less; lawyers, 29% less, and doctors, 16%, according to a 2010 study by Harvard economics professors Claudia Goldin and Lawrence F. Katz. "Business occupations place heavy penalties on employees who deviate from the norm," Goldin and Katz write in the study.

5. "I'm your best friend "

For the six out of 10 workers who say they've considered a boss a friend, this won't come as a surprise: Being the boss's pal, or pet, comes with perks. Some bosses play favorites in obvious ways, like giving a particular subordinate the plum assignments or pushing upper management for his raise. Others are more subtle, seeming to treat all employees equally. But then they'll offer more guidance to a favored worker, or make sure she is introduced to the "right" people, says career and executive coach Roy Cohen. And as long as the relationship works, everyone can benefit: Good relationships tend to lead to higher worker engagement; compatibility can help a worker get a raise or a promotion; everyone likes to work with people they like and trust.

But the footing is never strictly equal when one friend can fire the other. "You have to be very careful," says Cohen. The boss is still evaluating your compensation and performance, and the minute there's a problem or a disagreement over either, feelings get hurt. To keep a relationship friendly, without crossing the line into friends territory, avoid talking about sensitive personal issues, he suggests: No matter how close you might feel, ultimately there is always the chance that your boss will use that information in a way that serves his purposes, not yours.

6. " And your worst enemy."

But sometimes, the boss is your worst enemy. Just as a good relationship with your boss can bolster your career, a lousy one can tank it. Or worse. One study found that, in incidences of "workplace bullying" -- "repeated and persistent attempts by one person to torment, wear down, frustrate or get a reaction from another," according to the Society for Human Resource Management the boss is the bully 72% of the time. Nearly half of people who were bullied at work suffered stress-related health problems, according to the Workplace Bullying Institute. Even if your relationship doesn't deteriorate to that level, your communication can be strained if your boss doesn't keep his word, gives you the silent treatment, invades your privacy or deflects blame from himself -- all of which lead workers to experience "more exhaustion, job tension, nervousness, depressed mood and mistrust," a Florida State University study found. Worst case, this kind of behavior from the boss can even kill you: A 2008 study published in the Journal of Occupational and Environmental Medicine found that employees who had worked for four years under a boss who was uncommunicative, inconsiderate or opaque were 60% more likely to have a heart attack.

7. "I don't promote based on performance."

Usually, workers have to do a good job to get promoted. But in many cases, that's not enough. Who rises (and who doesn't) is a mix of factors, most of which workers have no real control over, including supervisors' preferences, organizational rules and company culture. In some organizations, particularly larger, more traditional companies, seniority may be the main factor in promotion decisions, says Tony Deblauwe, founder of HR consulting firm HR4Change. Seniority-based promotions are more common in the U.S. than in other countries, according to a 2004 study in the Socio-Economic Review, and "more popular than economic explanations would allow." Compatibility with the boss is critical, too, Deblauwe says: "Who you know makes a big difference, particularly the higher up you go."

The reverse is also true: Being smart and capable doesn't even guarantee your job. One manager in a small Arizona investment planning firm, who declined to give his name to preserve company morale, fired a subordinate whom he says was "very smart," with good credentials and a degree from a prestigious university. But the manager also found him difficult and hard to supervise, and ultimately fired him: "His strained relationship with me was a big factor in this decision."