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They may not be able to talk, but babies as young as seven months are able to subconsciously recognise fear in someone's eyes, new research claims.

Infants can read human expressions by looking at the whites of the eyes - or sclerae - in split seconds.

And they seem to react more in response to fear, than happiness, according to the study.

Infants can read human expressions by looking at the whites of the eyes - or sclerae –in split seconds, according to a new study. And they seem to react more (stock image) in response to fear, than happiness

Scientists from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig conducted EEG (electroencephalography) tests, which involved babies wearing a skull cap fitted with electrodes.

In the first experiment, 24 babies undergoing the tests were shown images of eyes without any other facial features, either reacting fearfully or showing happiness.

The activity in the babies' brains changed more in response to fear than happiness. 

A pair of fearful or surprised eyes (stock image) has larger whites than eyes showing other emotions, such as happiness, when they tend to show the smallest amount of white. The study claims that babies read this cue in just 50 milliseconds and react to fear stronger than happiness

The same result was seen in a second experiment when 22 babies were shown sclerae when the gaze was direct rather than averted.

In each experiment, the images were presented for just 50 milliseconds, which is beyond the threshold of conscious perception, according to the study published in the journal Proceedings of the National Academy of Sciences.

A pair of fearful or surprised eyes has larger whites than eyes showing other emotions, such as happiness, when they tend to show the smallest amount of white.

It is thought that the human eye's prominent white sclera is important in social interactions.

While scientists have previously found evidence for brain mechanisms that allow for the unconscious detection of eye cues in adults, they didn't know how early in development this ability emerges - until now.

'The current study provides neural evidence for the unconscious detection of emotion and gaze cues from the sclera in seven month-old infants,' said Dr Sarah Jessen, of the Max Planck Institute for Human Cognitive and Brain Sciences. 

'Our findings demonstrate the existence of fast, efficient and reliable social cue detection mechanisms in the human infant brain that likely provide a vital foundation for the development of social interactive skills.'

Scientists from of the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig conducted EEG (electroencephalography) tests, which involved babies wearing a skull cap fitted with electrodes. This stock image shows a four-year-old girl having an EEG test, with her brain activity shown on the screen

Humans are the only primates that have sclerae. For example, apes' are completely dark.

Experts believe that the white of the eye evolved as a communication aid to allow humans to see where other people were looking, because direction is linked to emotional states.

Women's brains have more hardwiring than men's to read emotions and one consequence of this is that women have more white in their eyes than men.

While apes may miss out on this extra communication tool, their lack of sclerae mean that their prey doesn't know where they are looking or whether they have been spotted - giving the creatures a greater chance of hunting success.

Humans are the only primates that have sclerae. For example, apes'are completely dark. This means that their prey doesn't know where they are looking or whether they have been spotted - giving the creatures a greater chance of hunting success.