"Children may not understand political alliances or intellectual argumentation, but they surely understand rubber bands and fistfights."--Steven Pinker, from The Stuff of Thought: Language as a Window into Human Nature (Viking, 2007).
SOMETIMES A CIGAR is just a cigar. Then again, mischief is the hot smoke that curls off the end of a lit intellect. And sometimes a diamond in the rough is indeed just an ancient deposit of highly compressed carbon. But no facet of humanity's evolved "genius" as Aristotle put it more than 2,300 years ago, sparkles so brilliantly as our unique capacities for extra-literal description and comprehension.
Until recently, most professional sources have attributed our proficiency with language to a pair of knuckle-sized regions on the brain's left side called Broca's area and Wernicke's area. The former module was responsible for grammar, the latter for word meanings. But new technologies, featuring functional Magnetic Resonance Imaging (fMRI), have allowed scientists to probe non-invasively into the brains of healthy volunteers and to discover, first, that other parts of the brain share in these responsibilities and, second, that Broca's and Wernicke's regions contribute to other important tasks as well.
For some, such frustrating complexity spells the end of the "modularity" hypothesis that instructs the functional specialization of certain identifiable neural systems. For others, including psychologist Gary Marcus, author of The Birth of the Mind (Basic Books, 2004), new evidence suggests "not that we should abandon modules (the Swiss Army Knife view of the brain) but that we should rethink them--in light of evolution."
While he acknowledges that the brain's left hemisphere appears to be devoted to both language and problem solving, R. Grant Steen, psychologist, neurophysiologist, and author of The Evolving Brain (Prometheus, 2007), agrees with Marcus, defining language (as opposed to mere communication) in very practical, adaptive terms:
[L]anguage is a system of communication that enables one to understand, predict, and influence the action of others. Inherent in this definition is a concept of theory of mind: if communication is instinctual rather than having a purpose, then it should probably not be considered a language. If communication has a purpose, this assumes an awareness of other independent actors, whose actions can potentially be influenced.... [F]or communication to serve the needs of the listener as well as the needs of the speaker, the listener must be able to understand what the speaker is "really" saying. It is not enough to understand the literal meaning of speech.
Broadly stated, then, experts seek out the neural substrates and processes of figurative language comprehension in order to distinguish the biological bases of what makes humans most exceptional among animals. In the end, they hope as well to develop more effective means of restoring these extraordinary abilities to those who have lost them and, perhaps, to enhance such talents for the benefit of our collective future. Although the search has just begun, we have already learned a great deal.
Two intimately associated paradigms have suffered intense scrutiny in recent years. The standard model of figurative language processing--sometimes referred to as the "indirect" or "sequential" view--maintains that the brain initially analyzes passages for literal meaning and, if the literal interpretation makes no sense, then reprocesses the words for access to an appropriate figurative meaning. According to the related dichotomous model of "laterality," the brain's left hemisphere (LH) is responsible for processing literal language while its right hemisphere (RH) is enlisted only to decode figurative expressions.
Such paradigms were based on classic lesion …