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Rats seem to sigh with relief, researchers find
Posted July 26, 2005
Special to World Science
Rats seem to sigh with relief when an expected electrical shock fails to come, a
study has found.
Scientists trained rats to expect a shock after a signal, by repeatedly administering a shock after the
signal.
But during part of the training, the researchers also sometimes gave a second
signal, which meant that the expected shock wouldn’t come. Thus the rats were
trained to associate this signal with a reprieve.
After that second signal, the researchers found, the rats often took a deep breath—an act that in humans is correlated with
relief.
The researchers, with the Nencki Institute of Experimental Biology in Warsaw, wrote a paper on their findings
published in the July 20 advance online issue of the research journal
Physiology & Behavior.
They described the shocks
they gave as mild.
A deep breath, or a sigh, is a common action in many mammals that provides extra air to under-ventilated parts of the lungs,
wrote the researchers, Stefan Soltysik and Piotr Jelen.
“Sighs are also correlated with emotions,” they added, including anxiety, anger and resentment “and obviously, judging from the expression—sigh of relief—in many languages, with relaxation or relief.”
If sighs can be shown to occur particularly often in conjunction with a specific
mood, this might mean
they’re a sign of that mood, they added.
The researchers found that rats sighed more than seven times as often during the situation of relief, after the second
signal, than during a
situation of fear. They also sighed 20 times as often during relief as between trials, they added.
“This clear correlation of sighs with relief (from fear of the tail shock) supports our hypothesis that sighs in social mammals may function as signals of safety,” they
wrote.
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