Shedding tears of joy is something that would have happened to most of us, but the reason behind this occurring is now unraveled by the scientists.
Lead author of the work, Yale psychologist Oriana Aragon, who conducted a series of studies of the seemingly incongruous expressions, said that people may be restoring emotional equilibrium with these expressions. 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.
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 were most likely to cry at their child's graduation were most likely to want to pinch a cute baby's cheeks.
There was also some evidence that strong negative feelings might provoke positive expressions, like nervous laughter during confrontation of some difficult or frightening situations, and smiles have been found by other psychologists to occur during extreme sadness.
Aragon said that the insights advance the understanding of how people express and control their emotions, which was importantly related to mental and physical health, the quality of relationships with others, and even how well people worked together.
The study is due to be published in the journal Psychological Science.