The sound of a crying baby is almost impossible to ignore, no matter how hard you try.

Now scientists may have worked out why.

They’ve shown that an infant’s wails rapidly pull at the heart-strings, in a way that other cries don’t.

In fact, within just a blink of an eye, brain regions involved in processing emotions are hard at work.

It had been thought that the brain was incapable of processing such complex facets of sound in such a short time.

With other types of cry, including calls of animals in distress failing to elicit the same response, the finding suggests that the brain is programmed to see something special in a baby’s cry.

The idea comes from Oxford University scientists who scanned the brains of 28 men and women as they listened to a variety of calls and cries.

After 100 milliseconds, roughly the time taken to blink, two regions of the brain that respond to emotion lit up.

Their response to the baby’s cry was particularly strong, the Society for Neuroscience’s annual conference in New Orleans heard.

What is more, the response was seen in both men and women – and in people who had no children of their own.

Researcher Dr. Christine Parsons said: “You might read that men should barely notice a baby and step over it and not see any of them but it’s not true.

“There is a specialized processing in men and women which makes sense from an evolutionary perspective that both genders would be responding to these cues.

“The study was in people who were not parents, have no particular experience of looking after babies and yet they are all responding at 100 ms to these particular sound, so this might be a fundamental response present in all of us regardless of parental status.”

Colleague Katie Young added that it likely takes a bit longer for someone to recognize their own baby’s call.

“When it comes to differentiating your own baby’s sound, it might be that this happens much later in time because you will be doing much more fine-grained analysis.”

Previous work from the Oxford team showed that our reactions are also speeded up by the sound of a crying baby.

Adults did better on an arcade game that requires speed, accuracy and dexterity, when they heard the sound, than they did after being recordings of adults crying or high-pitched bird song.

Morten Kringelbach, who co-led that research and supervised the latest project, said then: “Few sounds provoke a visceral reaction quite like the cry of a baby.

“For example, it is almost impossible to ignore crying babies on planes and the discomfort it arouses, despite all the other noises and distractions around.”

The findings are not just of general interest, they also have a practical purpose.

Understanding out how the healthy brain responds to babies’ cries could shed light on post-natal depression, in which mothers struggle to bond with their newborn, and lead to new treatments.