Observe whether two people use metaphors in conversation with each other if you want to guess how close they are as friends. Or sharpen your ability to tune into other people's emotional or mental states by observing the metaphors they use. Why is this? Because metaphors can in fact help one to 'mind read,' report Andrea Bowes and Albert Katz of the University of Ontario in Canada in Springer's journal Memory & Cognition.

Metaphor is a type of language that forms part of our daily conversations and communication. In this type of language, the literal or usual meaning of words and phrases is altered to convey some other, typically non-literal meaning. For instance, Juliet wasn't literally the sun -- Shakespeare had other intentions in mind. Although once considered an intentionally misleading and mentally taxing form of language, current research shows that metaphors are commonly used in conversation and are understood with relative ease.

Through three experiments, Bowes and Katz showed that people were better able to infer the mental and emotional state of others after reading metaphors, whether embedded in passages or just by themselves.

The ability to understand what another person might be feeling or thinking is called Theory of Mind by experts. It is found to differing degrees with each person, and is often impaired in autistic populations. One way that Theory of Mind is tested is through the Reading the Mind in the Eye Test (RMET), in which participants have to correctly identify the emotions or mental state displayed in black and white photographs of 36 pairs of eyes. Bowes and Katz showed that reading metaphors led to better performance on the RMET than reading literal sentence counterparts.

In one of the experiments, 39 participants first read either metaphorical or literal sentences as part of a story. They were then given a surprise Theory of Mind task. The participants who read the metaphorical sentences were significantly better at identifying the correct emotions in the sets of pictures they were presented with in the Reading the Mind in the Eye Test.

In another study, they were given short stories and asked to rate the speakers on a variety of interpersonal and social characteristics. Speakers who used metaphors in conversation with one another were also judged to be closer friends than those who did not use this figure of speech.

The evidence suggests that the mere act of reading metaphors activates embodied social experiences as part of the act of comprehension. This helps a person to be more sensitized to the mental states of others -- and to a greater extent than when they are reading literal sentences.

"The research explains why we speak differently with friends and family than with strangers, and shows how we make friends and meet partners simply with the style of language we use," says Bowes. "It provides novel evidence that metaphor plays a special role in orientating one to the mental state of others."

"Our findings, along with some others, also stress the importance of literature in fostering and understanding human empathy," adds Katz. "Reading fiction in general, and metaphors specifically, indeed promotes people's ability to identify the emotions or mental state of others."