"People may be restoring emotional equilibrium with these expressions," said Yale University psychologist Oriana Aragon, lead author of research.
"They seem to take place when people are overwhelmed with strong positive emotions, and people who do this seem to recover better from those strong emotions," said Aragon.
There are many examples of responding to a positive experience with a negative emotion. A crying spouse is reunited with a soldier returning from war.
Teen girls scream at a Justin Bieber concert and so do soccer players as they score a winning goal. The baseball player who hits a winning home run is pounded at home plate by teammates. And when introduced to babies "too cute for words," some can't resist pinching their cheeks.
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Aragon and her colleagues at Yale ran subjects through some of these scenarios and measured their responses to cute babies or happy reunions.
They found that individuals who express negative reactions to positive news were able to moderate intense emotions more quickly.
They also found people who are most likely to cry at their child's graduation are most likely to want to pinch a cute baby's cheeks.
There is also some evidence that strong negative feelings may provoke positive expressions; for example nervous laughter appears when people are confronted with a difficult or frightening situations, and smiles have been found by other psychologists to occur during extreme sadness.
"These insights advance our understanding of how people express and control their emotions, which is importantly related to mental and physical health, the quality of relationships with others, and even how well people work together," she said.
The study was published in the journal Psychological Science.