Recently, we identified  20 key things the best bosses try to do every day. Here's another exercise: Think about the worst boss you've ever known.

New research suggests it's likely this boss had one  bad habit that made you dislike working for him or her. And frankly, that habit is a surprising one.

We're talking about two bodies of research, actually. First, a Harris Interactive poll last year asked employees to disclose things bosses did that drove them crazy--and they came up with nine bad behaviors. These make sense, and we'll go through them below. 

But an even more recent study came up with an even worse behavior--and it's something employees didn't even identify on their own.

First off, here are the top-nine bad boss behaviors that employees complained about in the Harris poll (in reverse order of how many of the employees complained about them). Then, we'll get to the most surprising one.

Bonus content: 7 Things Great Leaders Always Do (infographic).

1. My boss doesn't ask about my life outside of work. (23 percent)

This bad behavior suggests a failure to recognize that employees are actually people--rather than just names on an org chart.

2. My boss won't talk on the phone (or in person). (34 percent)

Bad behavior suggests either a lack of interest or a lack of flexibility.

3. My boss doesn't know my name. (36 percent)

Bad behavior is almost self-explanatory, reflects a lack of caring.

4. My boss doesn't offer constructive criticism. (39 percent)

Bad behavior here could mean either a lack of any feedback, or a lack of tact in providing neutral or negative feedback.

5. My boss takes credit for others' ideas. (47 percent)

Bad behavior suggests either complete lack of leadership and ethics or inability to communicate effectively.

6. They refuse to talk to subordinates. (51 percent)

Bad behavior suggests hubris, potentially disorganization.

7. They don't take time to meet with employees. (52 percent)

Bad behavior suggests lack of caring, inability to communicate well.

8. They don't give clear directions. (57 percent)

Bad behavior suggests either lack of communication ability or lack of vision.

9. They don't recognize employee achievements. (63 percent)

Bad behavior here is obvious--nobody likes to be unappreciated.

These all make sense, even if some are a bit similar to others.  But there's another behavior that a more recent body of research found--and it's one that employees themselves didn't really identify. Instead, it became apparent only when independent observers looked at their situations and realized what was going on.

It was this: My boss is inconsistent.

If you're going to be bad, be consistently bad.

Employees suffered a greater negative effect on their happiness and productivity when their boss inconsistently displayed bad behavior than when the boss was consistently bad.

"Intuitively, you would think the more fairness you get, the better. But that's not what we demonstrated. It's better if supervisors are a consistent jerk than if they're fair sometimes and not fair other times. People want to know what they can expect when they come into work," the lead researcher on the study out of Michigan State University, Fadel Matta, told The Washington Post.

"All I can say is that I wish I was working with someone else."

The research was comprised of two studies. The first was a lab experiment, in which college students who were hooked up to heart monitors were told to perform a cognitive task (estimating a hypothetical company's stock price).

One third of the students were given positive feedback. A second third was told that they were doing poorly (I found the examples of negative phrases amusing: "All I can say is that I wish I was working with someone else," and "It sucks to work with an unmotivated person.")

The final third heard a mix of the two--some positive reinforcement, combined with negative feedback. The employees who received positive feedback did best, but it wasn't the ones who received negative feedback who did worst--it was instead the ones who got the mixed messages.

At least let me know what to expect.

Separately, about 100 workers and their bosses were asked to complete surveys over a three-week period. The employees were being tested for their perception of fairness while bosses were being tested for their ability to maintain self control.

"Again," the Post reported, "employees who had unpredictable managers were more likely to be stressed, dissatisfied with their jobs and emotionally exhausted than those who said they were always treated unfairly."

What do you think? Is inconsistency really the hidden cardinal sin of leadership and management? Let us know in the comments below, or contact me directly. Also, don't forget to check out the free bonus infographic: 7 Things Great Leaders Always Do.