Scientists Find Brain's Irony-Detection Center!

OK, that headline is a bit hyperbolic, but not as hyperbolic as you might think. Using magnetic resonance imaging, scientists seem to have located a part of the brain centrally involved in grasping irony.

The IronyBrain2.JPGFrench research team that made the latest contribution to this effort presents its findings in the current issue of the journal NeuroImage. Referring to a part of the brain known as the "ToM network," the researchers write, "We demonstrate that the ToM network becomes active while a participant is understanding verbal irony."

This isn't just one of those "shot in the dark" MRI studies, where you see what brain regions happen to light up when people engage in a particular mental activity. The ToM network has been the focus of previous work on irony apprehension, and enough is known about it to give us some ideas about the particular role it could play in that apprehension.

Here's how the experiment worked. The researchers prepared short written stories, and each story came in two versions. Both versions contained a sentence that could be read either literally or ironically, with the correct reading depending on how the context had been set earlier in the story. In one story, for example, one opera singer says to another, "Tonight we gave a superb performance," and whether the sentence is ironic or literal depends on whether the performance had been described earlier in the story as a failure or as a success. The researchers had correctly predicted that the ToM network would show more activity when the sentence, read in context, was ironic than when it was literal.

ToM stands for "theory of mind," which in turn refers to the fact that we naturally attribute beliefs and intentions and emotions to people we interact with. That is, we develop a "theory"--though not necessarily a theory we're consciously aware of--about what's going on in their minds. (An inability to do this is thought to play a role in autism.) And this "theory" in turn shapes our interpretation of things people say. The "ToM network" is a brain region--or, really, a network of different brain regions--that seems to play an important role in the construction of these theories.

It makes sense that parts of the brain involved in theorizing about other people's minds would be involved in grasping irony. After all, detecting irony means departing sharply from the literal meaning of a sentence, something it's hard to do without having a "theory" about the intent behind the sentence.

Consider Twitter: I sometimes wonder, reading sarcastic tweets from someone I know, how they're interpreted by people less familiar with the tweeter's mind than I am. And it seems to me that people who don't know the tweeter but correctly sense the irony must, in the process, develop a kind theory about the tweeter's mindset.

As usual with scientific "breakthroughs," this experiment turns out to build on others. There have been (who knew?) a fair number of brain imaging studies about irony. And some had implicated one or more parts of the "ToM network." But this study, according to the authors, is the first to implicate the network so broadly, showing increased activation in four main ToM regions.

Of course, there may be parts of the brain outside of the ToM network that are involved in grasping irony. (For all I know there's a part of the brain involved in processing the concept of "opposite," and maybe that's also activated when we apprehend irony.) This points to what is perhaps the main piece of hyperbole in the headline above: the suggestion that there is a single irony detection "center" in the brain. There presumably are multiple centers, and presumably all of them, like the ToM network, do other things as well.

In fact, one irony study showed activation of part of the limbic system. But the limbic system is associated with emotion, so this could reflect an emotional reaction to the apprehension of irony (or perhaps a reaction to the seeming paradox--Why would you call a bad opera performance good?--that is then resolved via the subsequent apprehension of irony). What's interesting about the ToM network is that the prior understanding of its function provides good reason to suspect that its heightened activity signifies involvement in the actual grasping of irony.

In general I don't pay much attention to brain imaging news flashes--you know, scientists find the part of your brain that lights up when you're meditating or doing crossword puzzles or mowing the lawn. I mean, presumably everything we feel or think has some correlate process in the brain, so confirmation of this fact isn't by itself a man-bites-dog story. Still, these findings are scientifically important, because bit by bit they're building up a functional map of the brain, and that will be important for therapeutic and other purposes. And this latest finding, though in some ways tentative, underscores how high-resolution this map could ultimately be.

According to Science Daily , which reported these findings this weekend, the scientists who did this experiment "hope to expand their research on the ToM network in order to determine, for example, whether test participants would be able to perceive irony if this network were artificially inactivated." Yes, that would be interesting. Also interesting would be to see what happens if the network is artificially (and subtly) activated. Wouldn't it be nice if, rather than have to explain to people that you were only kidding, you could just push a button, and they'd get the joke?

[Notes: (1) Of course, the usual caveats apply: this experiment may not be confirmed via replication, etc., (2) My speculations about the meaning of the fMRI study that implicated the limbic system are just that--rank speculation--and I haven't yet seen how the work was interpreted by the scientists who did it.]

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Robert Wright is the author of The Evolution of God and a finalist for the Pulitzer Prize. He is a former senior editor at The Atlantic.

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