Metaphors present a problem for anybody trying to explain language, or anybody trying to teach a computer to understand language. It is clear that nobody is supposed to take the statement, “Sarah Palin is a barracuda” literally.
However, we can imagine that such phrases are memorized like any other idiom or, for that matter, any word. Granted, we aren’t sure how word-learning works, but at least metaphor doesn’t present any new problems.
At least, not as long as it’s a well-known metaphor. The problem is that the most entertaining and inventive language often involves novel metaphors.
So suppose someone says “Sarah Palin is the new Harriet Miers.” It’s pretty clear what this means, but it seems to require some very complicated processing. Sarah Palin and Harriet Miers have many things in common. They are white. They are female. They are Republican. They are American. They were born in the 20th Century. What are the common characteristics that matter?
This is especially difficult, since in a typical metaphor, the common characteristics are often abstract and only metaphorically common.
Alzheimer’s and Metaphor
Some clever new research just published in Brain and Language looked at comprehension of novel metaphors in Alzheimer’s Disease patients.
It is already known that AD patients do reasonably well on comprehending well-known metaphors. But what about new metaphors?
Before I get to the data, a note about why anybody would bother troubling AD patients with novel metaphors: neurological patients can often help discriminate between theories that are otherwise difficult to distinguish. In this case, one theory is that something called executive function is important in interpreting new metaphors.
Executive function is hard to explain and much about it is poorly understood, but what is important here is that AD patients are impaired in terms of executive function. So they provide a natural test case for the theory that executive function is necessary to understand novel metaphors.
In this study, AD patients were as good as controls at understanding popular metaphors. While control participants were also very good at novel metaphors, AD patients had a marked difficulty. This may suggest that executive function is important in understanding novel metaphors and gives some credence to theories based around that notion.
This still leaves us a long way from understanding how humans so easily draw abstract connections between largely unrelated objects to produce and understand metaphorical language. But it’s another step in that direction.
M AMANZIO, G GEMINIANI, D LEOTTA, S CAPPA (2008). Metaphor comprehension in Alzheimer’s disease: Novelty matters Brain and Language, 107 (1), 1-10 DOI: 10.1016/j.bandl.2007.08.003