For the study, the researchers investigated how the brain recognizes that the first phrase means the same as the second, and have suggested that we use both hemispheres to understand idioms.
Dr. Alice Proverbio, from the University of Milano-Bicocca, used electrophysiological and LORETA source reconstruction analysis to investigate the role of the two cerebral hemispheres in idiom comprehension.
They analyzed the brain activity of 11 students, and found that idiomatic sentences activated the right middle temporal gyrus (after 350ms) and the right medial frontal gyrus (at 270-300 and 500-780ms).
They matched all phrases for length and familiarity, but the students still took longer to associate an idiomatic phrase with a linked word than to associate a literal phrase with its linked word.
Thus, they suggested that idioms are more difficult to understand, and denote superior levels of language use and processing.
The findings also shed light on whether the brain tries to understand a familiar idiom literally before it understands it as a metaphor.
The left inferior frontal gyrus, the part of the brain that apparently was used to suppress literal meaning, was not specifically activated by idiom comprehension.
But the limbic regions, which are involved in emotional responses, were at 400-450ms.
"Though the interpretation of language involves widespread activation bilaterally, the right hemisphere has a special role in the comprehension of idiomatic meaning," concluded Proverbio.
The study has been published in the open access journal BMC Neuroscience.