Why reading disgusting things makes you gag

Have you ever wondered why reading a good book can be almost as moving as events in real life? It may be because you use the same brain region to make sense of both.

Previous studies indicated that the anterior insula and adjacent frontal operculum (brain regions known collectively as the IFO) are activated both when we observe someone experiencing an emotion such as disgust, delight or pain, and when we experience it ourselves. This is believed to be what allows us to empathise with others and understand their intentions. But what if the emotion is merely imagined, such as when reading about it. Is the IFO active here too?

To find out, Mbemba Jabbi and colleagues at the University of Groningen in the Netherlands focused on the feeling of disgust. They placed quinine, which has a nasty bitter taste, onto the tongues of 12 volunteers while they lay in an MRI scanner. They were also asked to watch a video of someone simulating disgust and read a story about something disgusting.

The team found that the IFO was activated in all three tasks (PLoS One, DOI: 10.1371/journal.pone.0002939). They say that this similarity between first-hand experience and imagination helps to explain why fiction can be so compelling. “This is why books and movies work – they stimulate the area of the brain which is involved in what it really feels like to be disgusted,” says Christian Keysers, a member of Jabbi’s team.

The team suggest that reading about delight or pain also activates the IFO.

From issue 2669 of New Scientist magazine, 13 August 2008, page 15

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