Answer: Chatting with teammates at work is a good way to get to know each other. But we all have that certain someone who drops by with a cup of coffee in her hand and settles in for a solid 10 minutes while you stare at her with helpless, pleading eyes.

When your colleague isn’t reading your social cues, there’s a good chance that she’s not perceiving what you’re doing. To demonstrate, take this short awareness test for yourself. Go ahead, we’ll wait. It’s only one minute long. Did you pass? This test is based on a study in unconscious bias first conducted by psychologist Ulric Neisser in 1979.  79% of first-time participants in the study did not pass.

Later research expanded on Neisser’s work and found that unconscious biases also influence perception. The research suggests that, when people have a defined goal (like chatting with you), they can have tunnel vision that keeps them from noticing everything else. No matter if you have dozens of apps open on your computer, or that your desk is buried in stacks of paper. Consider, also, that your teammate may not be directly linked to or affected by the tasks you’re doing. That lack of connection to your job can make her perceive your work as not important, giving her even narrower tunnel vision.

The best way to take back control of your time is to be firm.  Point out the work you are trying to do to bring your tasks to your colleague’s conscious attention. Be blunt about the fact you can’t talk right now and what your deadlines are. You can diffuse the tension by adding a touch of tasteful humor, if you like, but be firm.

Remember, it’s not personal, it’s perception.