Rats Seem to Sigh with Relief, Researchers Find 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 wouldn¹t 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. ³Sighs are also correlated with emotions,² they added, including anxiety, anger and resentment ³and obviously, judging from the expression‹sigh of relief‹in many languages, with relaxation or relief.² If sighs can be shown to occur particularly often in conjunction with a specific mood, this might mean they¹re 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. ³This 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,² they wrote. Source: Posted July 26, 2005 Special to World Science http://www.world-science.net