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The researchers put
of paper under the dogs' eyes. They used the
to check if the dogs cried. The scientists found that when dogs saw their
after five to seven hours of
, they shed tears. A researcher said he had never heard of
crying tears of joy, when reuniting with their owners. He said: "Tears might play a
in the deepening of mutual
." He thinks dogs' tears may make humans love their dogs
. He said: "It's
that dogs who show
eyes during human interaction would be cared for more."
