「情けは人のためならず」は科学的にもおおむねホント。親切をした本人も少し幸せになる

A Japanese proverb says that kindness to others will come back to you. Science seems to agree. In one study, people did five kind acts in a week, such as helping a friend.

The people who did all five on one day felt happier. A review of many studies also found that being kind makes us a little happier. Even children under two looked happier when they gave treats away.

The Japanese proverb "Nasake wa hito no tame narazu" is often misunderstood. Its real meaning is that kindness to others eventually comes back to you, and psychology largely supports it. In a study by Sonja Lyubomirsky, participants performed five acts of kindness in a week, such as giving blood or writing a thank-you letter.

Only those who did all five on a single day showed a clear rise in happiness. In 2018, a team at Oxford University combined the results of many experiments and found that acts of kindness do increase the happiness of the people who perform them, although the effect is small to medium. Even toddlers seem to enjoy giving. Children under two looked happiest when they shared their own treats.

The Japanese proverb "Nasake wa hito no tame narazu" is often misread as a warning that kindness spoils people. Its original meaning is that kindness eventually comes back to the giver, and psychological research mostly supports that reading. In work reported by Sonja Lyubomirsky and colleagues, students who did five acts of kindness each week became clearly happier only when they did all five on a single day, not when they spread them across the week, perhaps because small deeds scattered over several days blend into routine. That one-day finding, however, comes from a small study.

A 2018 meta-analysis led by researchers at Oxford University pooled experimental studies and concluded that kind acts do raise the actor's well-being, but only to a small-to-medium degree, and found no sign of publication bias among the included studies. Motive matters too. Kindness performed out of obligation may be exhausting rather than rewarding.

The reward of giving seems to appear early in life. In a Canadian study, researchers coded the facial expressions of toddlers under two years old as they gave treats to a puppet or received treats themselves. The children looked happier giving than receiving, especially when they gave away their own.