If you've ever started a sentence with, "If I were you . . . " or found yourself scratching your head at a colleague's agony over a decision when the answer is crystal-clear, there's a scientific reason behind it. Our own decision-making abilities can become depleted over the course of the day causing indecision or poor choices, but choosing on behalf of someone else is an enjoyable task that doesn't suffer the same pitfalls, according to a study published in Social Psychology and Personality Science.

The problem is "decision fatigue," a psychological phenomenon that takes a toll on the quality of your choices after a long day of decision making, says Evan Polman, assistant professor of marketing at the Wisconsin School of Business, and coauthor of the study.

Physicians who have been on the job for several hours, for example, are more likely to prescribe antibiotics to patients when it's unwise to do so, according to 2014 research published in the Journal of the American Medical Association. "Presumably it's because it is simple and easy to write a prescription and consider a patient case closed rather than investigate further," Polman says.

But decision fatigue goes away when you're making the decision for someone else. When people imagine themselves as advisers and imagine their own choices as belonging to someone else, they feel less tired and rely less on decision shortcuts to make those choices. "By taking upon the role of adviser rather than decision maker, one does not suffer the consequences of decision fatigue," he says. "It is as if there is something fun and liberating about making someone else's choice."

Getting the best advice, however, will rely on the personality of your adviser. Surprisingly, the worst person to ask is someone who loves to help others, says Polman. That's because a person who cares deeply about others can also suffer from decision fatigue when advising others, presenting the potential for bad advice, says Polman. "For example, research has found that nurses who are particularly high in empathy experience career burnout more often than nurses who are less empathetic," he says.

The best person to ask is someone relatively dispassionate to your circumstances; someone who doubts others and thinks highly of themselves, says Polman. "It may not be a coincidence that when it comes to offering advice, we might say, 'Here's my two cents,' yet when we ask for others' advice, we say, 'Penny for your thoughts,'" he says. "It is this kind of self-interested person who values her own opinion over others who is a good candidate to make choices for others and advise others. She is less drained by making those choices, and hence makes choices that are not susceptible to decision fatigue."

Getting input from others not only offers a fresh perspective and thought process, it often also includes riskier choices. While this sounds undesirable, it can be quite good, says Polman. "When people experience decision fatigue—when they are tired of making choices—they have a tendency to choose to go with the status quo," he says. "But the status quo can be problematic, since a change in course of action can sometimes be important and lead to a positive outcome."

In order to achieve a successful outcome or reward, some level of risk is almost always essential. "People who are susceptible to decision fatigue will likely choose to do nothing over something," he says. "That's not to say that risk is always good, but it is related to taking action, whereas decision fatigue assuredly leads to inaction and the possible chagrin of a decision maker who might otherwise prefer a new course but is unfortunately stymied."

Just because you can make good choices for others doesn't mean you'll do the same for yourself, Polman cautions. "Research has found that women negotiate higher salaries for others than they do for themselves," he says, adding that people slip in and out of decision roles.

"Despite the extensive experience that people have making choices for themselves and others, they struggle to transfer information gained from one role, choosing for others, and applying it to another, complementary role choosing for themselves."