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The
, from Azabu University and Jichi Medical University, put
of paper under the dogs'
. They then checked to see if, and when, the dogs cried. The scientists found that when the humans and dogs were reunited after five to seven
of
, the dogs shed tears. Researcher Takefumi Kikusui said: "We had never heard of the
that animals shed tears in joyful
, such as reuniting with their owners." He added: "Their tears might play a
in the deepening of mutual relationships." He believes the tears may make humans love their dogs more. He said: "It's possible that dogs who show
eyes during human
would be cared for more."