The advice to be a nicer person assumes that niceness is a straightforward good, a dial you should turn up as far as it will go. The research is more interesting than that. Niceness carries real benefits and real costs, and the whole art of it lies in telling the useful kind apart from the kind that quietly works against you.
It helps to start with the good news, because there is plenty of it.
Niceness genuinely improves the parts of life people care about
Agreeableness, the personality trait that captures warmth, cooperativeness, and a tendency to trust and accommodate others, is the closest thing psychology has to a measure of niceness. And on the outcomes most people say matter most, it looks good. In the research of Timothy Judge and colleagues, agreeableness was associated with higher life satisfaction, stronger social networks, more involvement in one’s community, and lower levels of stress.
That is not a trivial list. It describes, more or less, the ingredients people name when they describe a good life. Whatever else niceness does, it appears to buy you a warmer and less stressful existence, which is a strong argument for the basic disposition before we get to its complications.
The bill that comes with it
The complications are real, though. In the same body of work, published in the Journal of Personality and Social Psychology in 2012, Judge and his co-authors also looked at earnings, and here niceness was a liability. Analyzing surveys of around 10,000 workers over roughly two decades, they found that more agreeable people earned less, with the least agreeable men out-earning the most agreeable ones by about 18 percent.
The likely reason is not mysterious. Agreeable people are less inclined to push hard for themselves, to negotiate aggressively, or to risk a confrontation over what they are owed, and others learn that they can be leaned on without much pushback. It is worth adding the usual cautions: this is correlational, the effect was tangled up with gender in ways that reflect bias as much as behavior, and it comes from one program of research. But the direction is a useful warning. In the specific situations that reward self-advocacy, undiluted niceness has a price.
When niceness turns on the nice person
There is a second cost, and it is the one that does the most quiet damage. It has to do with the difference between caring about others and erasing yourself in the process.
The psychologists Heidi Fritz and Vicki Helgeson drew this line carefully. They distinguished ordinary communion, a healthy, caring orientation toward other people, from what they called unmitigated communion, a focus on others so complete that the self drops out of the picture. The unmitigated version means neglecting your own needs, deriving your sense of worth from others’ approval, and finding it very hard to say no. Across their studies, this pattern was linked to psychological distress, including depressive symptoms.
The crucial finding is what was not to blame. Healthy caring was not associated with distress; the self-neglect was. Caring about people while remaining a person who also has needs is a different thing from caring as though having needs would cancel your value. The first is warmth. The second is a slow erosion, and it does not actually serve the people on the receiving end any better.
The art, then, is calibration
Put these findings together and the instruction that falls out is not be less nice. It is keep the warmth and detach it from its two failure modes.
The first failure mode is the inability to advocate for yourself, which turns niceness into a standing invitation to be overlooked. The second is the collapse of your own needs into everyone else’s, which the research suggests is not a purer form of kindness but a route to distress. Genuine niceness sits between them: warm by default, and firm when something actually matters, whether that is a salary, a boundary, or a no that needs saying.
A few limits are worth keeping in view. These are averages drawn from correlational studies, not laws that govern any single person, and the gendered patterns in particular say as much about how niceness is perceived and punished as about the trait itself. And niceness is not the same as goodness or kindness; a person can be pleasant and unkind, or blunt and deeply good.
Still, the shape of the evidence is clear enough to be useful. The nicest people, in the sense worth aspiring to, are not the most agreeable ones or the most self-sacrificing ones. They are the ones who stay warm without disappearing, which turns out to be better for them and no worse for anyone else.