New York, Jan 31 (IANS): Female rats often respond to fear by "darting" where they start running around like crazy when they sense threat, new research has found, suggesting that the findings could lead to better treatments for post-traumatic stress disorder (PTSD) in humans.

Till now it had been thought that in response to fear rats freeze in their tracks. That has been the consensus among scientists since 1899, when experimental psychologist Willard Stanton Small first noted the behaviour, the study said.

The new study suggests that response to fear may not be uniform among rats and that behaviour of male and female rats may differ.

In the study published in the online journal eLife, the researchers found that darting rats were more successful at integrating a process that suppressed the fear response.

"If we can harness whatever is going on when an animal becomes a darter, we could try to apply that to treatments in humans," said lead researcher Rebecca Shansky, assistant professor of psychology at the Northeastern University in Boston, US.

The researchers stumbled across the findings while performing a common behavioural test called "fear conditioning" in an effort to see how individual males and females differed in their fear responses, and to explore what brain changes related to those differences.

The test involved teaching the animals to associate a tone with a foot shock, and then -- with a video camera connected to a computer -- measuring the duration of their reaction as the training proceeded.

The researchers found that while some rats exhibited freezing, scores of the female rats not only did not freeze at the sound of the tone, they darted hither and yon, as if looking for an exit.