Oh, great. Now we know what the right parahippocampal gyrus does.

Or so declares an article in the New York Times:

The Science of Sarcasm (Not That You Care)

By DAN HURLEY
Published: June 3, 2008

There was nothing very interesting in Katherine P. Rankin’s study of sarcasm — at least, nothing worth your important time. All she did was use an M.R.I. to find the place in the brain where the ability to detect sarcasm resides. But then, you probably already knew it was in the right parahippocampal gyrus.

But of course. Other bloggers have already posted about this story (so go on, read more about sarcasm, social cognition and theory of mind there). The original research findings have yet to appear as a full-length publication, but Rankin and her colleagues presented this work at the recent American Academy of Neurology meeting in Chicago.

The NYT article continues:

Although people with mild Alzheimer’s disease perceived the sarcasm as well as anyone, it went over the heads of many of those with semantic dementia, a progressive brain disease in which people forget words and their meanings.

“You would think that because they lose language, they would pay close attention to the paralinguistic elements of the communication,” Dr. Rankin said.

To her surprise, though, the magnetic resonance scans revealed that the part of the brain lost among those who failed to perceive sarcasm was not in the left hemisphere of the brain, which specializes in language and social interactions, but in a part of the right hemisphere previously identified as important only to detecting contextual background changes in visual tests.

“The right parahippocampal gyrus must be involved in detecting more than just visual context — it perceives social context as well,” Dr. Rankin said.

It's not as simple as all that, Rankin et al. note in their own abstract. Worse performance in the Sarcasm test was also associated with greater atrophy in other sectors of the right temporal lobe and in the right superior frontal gyrus. Moreover, a 2005 study [BBC link via Of Two Minds] implicated a network of brain regions, primarily right ventromedial prefrontal cortex [they could not assess the importance of the right temporal lobe in their study]:

Dr Simone Shamay-Tsoory and colleagues (Neuropsychology, 2005) studied 25 people with prefrontal lobe damage, 16 with damage to the posterior lobe of the brain and 17 healthy volunteers.

. . .

The volunteers who had damage to their prefrontal lobes were unable to correctly interpret the sarcastic story, while all of the other participants could...

[Dr Shamay-Tsoory] said language areas on the left hand side of the brain interpret the literal meaning of words and the frontal lobes and the right side of the brain understand the social and emotional context.

An area called the right ventromedial prefrontal cortex then integrates the literal meaning with the social/emotional context, which will reveal any sarcasm.

"A lesion in each region in the network can impair sarcasm, because if someone has a problem understanding a social situation, he or she may fail to understand the literal language," she said.

Oh well, "whatever", nevermind. I couldn't get The Sarcasterizer to work, so there you go.

It's "certain" that nobody's gotten tired of the insincerity and detached irony that's so prevalent in today's "hip" discourse. There's nothing the the world quite as "thrilling" as stumbling across yet another Web page drenched in "disaffected" sarcasm. And "everybody's" constantly asking us where they can get "more" of this "precious" commodity.

UPDATE: bigger better multiple sarcasms.

References

[IN2-2.004] Detecting "Sarcasm" from Paralinguistic "Cues": Anatomic and Cognitive "Correlates" in Neurodegenerative Disease

Katherine Rankin, Andrea G. Salazar, Maria Gorno Tempini, Danijela Pavlic, Christine M. Stanley, Shenly Glenn, Michael Weiner, Bruce Miller.

OBJECTIVE: To investigate the structural neuroanatomy underlying neurodegenerative disease patients failure to understand sarcasm from dynamic vocal and facial paralinguistic cues. BACKGROUND: While sarcasm can be conveyed solely through contextual cues such as counterfactual or echoic statements, face-to-face sarcastic speech may be characterized by a specific paralinguistic profile that alerts the listener to interpret the utterance as ironic or critical, even in the absence of contextual information. DESIGN/METHODS: Ninety-one subjects (20 frontotemporal dementia, 11 semantic dementia [SemD], 4 progressive nonfluent aphasia, 28 Alzheimer's, 6 corticobasal degeneration, 9 progressive supranuclear palsy, 13 healthy older controls) were tested using the Social Inference-Minimal subtest of The Awareness of Social Inference Test (TASIT). Subjects watched brief videos depicting sincere or sarcastic communication and answered yes-no questions about the speakers intended meaning. RESULTS: All groups performed normally interpreting items on a Sincere control task, suggesting other cognitive impairments did not significantly account for Sarcasm task performance. Only the SemD group was impaired on the Simple Sarcasm condition. Subjects failing the sarcasm comprehension task performed more poorly on dynamic emotion recognition tasks, had more neuropsychiatric disturbances, but had better verbal and visuospatial working memory than patients who comprehended sarcasm. Voxel-based morphometry analysis of TASIT scores was performed using age, sex, total intracranial volume, and performance on the Sincere condition as covariates. Poorer sarcasm recognition correlated with right temporal lobe atrophy (anterior fusiform and parahippocampal gyrii, superior temporal sulcus), and atrophy to the right superior frontal gyrus and striatal structures (right caudate and left globus pallidus) (p less than 0.05, FWE). CONCLUSIONS/RELEVANCE: This study provides lesion data suggesting that the right posterior temporal lobe and dorsomedial frontal cortex are associated with recognizing and interpreting sarcastic irony using paralinguistic vocal and facial cues, consistent with functional imaging research examining neural correlates of voice prosody, facial emotion recognition, and perspective taking.

Shamay-Tsoory SG, Tomer R, Aharon-Peretz J. (2005). The neuroanatomical basis of "understanding" sarcasm and its "relationship" to social cognition. Neuropsychology 19:288-300.