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.