As the end of 2013 approaches, performance reviews are on the agenda at many companies. Before you start conducting them, though, you may want to know how criticism affects your employees' brains.

Daniel Goleman, the co-director of the Consortium for Research on Emotional Intelligence in Organizations at Rutgers University, explains in the Harvard Business Review how criticism triggers anxiety and negative emotions. When we're told about things that we're doing wrong, Goleman says, it "shuts us down, puts us on the defensive, and narrows our possibilities to rescue operations."

On the flip side, when you ask employees about their dreams and how to achieve them, they open up, think creatively, and feel good.

Goleman notes that for his book Focus: The Hidden Driver of Excellence, he interviewed Richard Boyatzis, a professor at the Weatherhead School of Management at Case Western Reserve University who tracked brain activity to find the best coaching practices. "Talking about your positive goals and dreams activates brain centers that open you up to new possibilities. But if you change the conversation to what you should do to fix yourself, it closes you down," Boyatzis says in the book.

Boyatzis's research, Goleman writes, found that positive interviews about goals triggered peoples' reward center and released dopamine, the chemical responsible for feeling pleasure. But negative interviews that focused on problems and criticism did the exact opposite, releasing anxiety and making the interviewees defensive and unable to focus on how to improve themselves.

Performance reviews are not a time you coddle your employees, Goleman says. They are an opportunity for you as a leader to give honest feedback and try to help members of your team improve in areas they are struggling. To do that effectively, there needs to be a balance of positive and negative, he says, citing Boyatzis's words: "You need the negative focus to survive, but a positive one to thrive. You need both, but in the right ratio."

What do you think? How do you use reviews to help your employees improve their performance at your company? Let us know in the comments below.