Prof Digby Tantum, Clinical Professor of Psychotherapy, at the University of Sheffield, believes that language plays only a part of in how humans communicate and that actually the brain is working hard to pick up tiny micro-signals that communicate what a person is thinking.

It explains how people often have a 'gut feeling' or intuition about a person or situation even if they cannot logically determine why.

And it may be the reason why commuters find it so difficult to maintain eye contact on a busy train. Too many people overloads the brain with too much subliminal information. In addition, it may also explain why laughter is infectious.