The customer is always right.

That's just a phrase, not a law. So if during your last-minute holiday shopping you feel the need to lash out at a retail or customer-service worker, just know the response from the employee may not always be so professional.

A research study out of Rutgers University, published in the Journal of Applied Psychology, finds there's no shortage of store and restaurant employees that will "retaliate" or "sabotage" difficult customers, even if it results in lost business.

After running their own experiments with workers and customers, then corroborating their findings with a study of more than 100 customer service employees, the researchers discovered employees typically make snap judgments to get even with a mean or difficult customer — in the moment, many workers don't have the ability to evaluate the situation and determine what response is best for everyone.

"If it's a call center type of situation, you might put someone on hold much longer than they actually should be on hold, because you're angry with them." co-author Rebecca Greenbaum told New Jersey 101.5. "In the very worst situation, it would be spitting in a customer's food if you're in the restaurant industry."

Greenbaum, a professor of human resources management at Rutgers, said this type of reaction is obviously not in the best interest of the "service provider," but it happens. Rude behavior by a customer can trigger feelings of hostility in a worker, and force the worker to "dehumanize" the customer, the research said.

"It goes against the philosophy that the customer is always right," she said. "If you step back and objectively consider everything, from an employee point of view, it doesn't really make sense to retaliate against a customer, even if they're being a jerk."

The silver lining

These impulsive emotions and thoughts may be human nature, but the right game plan by a manager could help quell the desire for revenge, researchers said.

A "high ethical climate" in the workplace could make employees less likely to retaliate, according to the research.

"Especially during the holiday season, when patience is wearing thin, employees should be reminded of the organization's ethical expectations," Greenbaum said. "Discussing the importance of treating customers with dignity and respect may ground employees when they are tempted to strike back at an awful customer."

Greenbaum said it's important that a manager's ethics policy "is not just window dressing" — that it's actually being applied in everyday interactions with customers.

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Contact reporter Dino Flammia at dino.flammia@townsquaremedia.com.