From Scientific American:
Metaphors make for colorful sayings, but can be confusing when taken literally. A study of people who are unable to make sense of figures of speech has helped scientists identify a brain region they believe plays a key role in grasping metaphors.
Vilayanur S. Ramachandran of the University of California at San Diego and his colleagues tested four patients who had experienced damage to the left angular gyrus region of their brains. All of the volunteers were fluent in English and otherwise intelligent, mentally lucid and able to engage in normal conversations. But when the researchers presented them with common proverbs and metaphors such as “the grass is always greener on the other side” and “reaching for the stars,” the subjects interpreted the sayings literally almost all of the time. After being pressed by the interviewers to provide deeper meaning, “the patients often came up with elaborate, even ingenious interpretations, that were completely off the mark,” Ramachandran remarks.
More here.