Reader 1: At my annual review, management told me they were already paying top dollar for my position and that I would have to move to a new position to earn more, so I did. I have since discovered that the person hired to fill my prior position is making a significantly higher salary than I make now. I am currently training her, and I can barely look her in the eye because of my anger and sense of unfairness.

Reader 2: I recently found out that my colleague is making about 25 percent more than I am. We have the same title, but she has a professional certificate; I have more experience and deliver better results. I’d like to negotiate for more money when our contracts come up for renewal.

A: I recently stumbled across a video about a study involving capuchin monkeys trained to exchange small rocks for treats. Monkey 1 was content to receive a piece of cucumber for each rock until she saw Monkey 2 next door being awarded a coveted grape for doing the same job. In response to this unfair setup, Monkey 1 threw a fit, rattling her cage and flinging her cucumber at the researcher.

Pay inequity among humans isn’t always a cucumbers-to-grapes comparison. So don’t go flinging anything in your boss’ face just yet.

First, take a hard look at what you and your co-worker bring to the table: education, experience, results. Is it possible your co-worker offers more value to the company? Or did he or she ask for more up front or do a better job of calling raise-worthy accomplishments to management’s attention? Try to see things from management’s perspective so you’re not blindsided.

Then forget about your co-worker (unless you honestly suspect an illegal bias based on race, sex, age, etc.). Build a case for a raise for yourself based on quantifiables: additional responsibilities, training that has boosted your performance or contributions you’ve made to the bottom line. Spelling out your value to the company is more likely to generate positive results than displaying grape envy.

If the boss insists the money isn’t there, consider asking for nonmonetary compensation such as permission to telecommute, flexible hours or additional leave.