We’re all familiar with the positive feeling of amusement we get when watching "America’s Funniest Home Videos" or when laughing about a good joke with friends at a party. What many people are less aware of, though, is the fact that humor actually is a prototypical human social emotional state that differentiates us from nearly all other animals.
With this knowledge, it’s tempting to ask how humor is processed on a neural basis by the human brain, and what function humor could play in humans in evolutionary terms. To stimulate future research on these and other questions, Jessica Black, PhD, Allan Reiss, MD, and I wrote a review paper, “Neural Basis of Humor Processing in Humans,” that was recently published online by Nature Reviews Neuroscience.
We also found evidence for altered humor processing in adults suffering from psychological or psychiatric disorders… Such findings are of potential clinical relevance as they provide valuable information on [the] conditions...
The central part of our review paper consists of a summary of all functional magnetic resonance imaging (fMRI) papers on humor that have appeared during the last 13 years. In our eyes, the findings of those studies nicely converge with previously derived psychological humor models in suggesting that humor perception involves two core processes.
In a first step, also referred as to the cognitive humor component, an apparent discrepancy or incongruity between two or more elements of incoming information is detected and resolved. For example, incongruity can be introduced by the occurrence of an unexpected twist in successive events, which then has to be resolved by associating the new outcome with an alternative meaning. In terms of functional neuroanatomy, one area of the temporal parietal cortex, the temporo-occipito-parietal junction, appears to be particularly well-suited for such incongruity processing. In a second step, incongruity resolution is then linked to a positive feeling of amusement or mirth, also referred as to the emotional humor component. The latter appears to be mainly maintained by high activity in reward-related brain circuits, making us feel good about the successful resolution of incongruity.
Along with reviewing the fMRI literature on the core processes involved in humor, we looked at the influence of sex, personality and brain disorder on humor processing. The available data indicates that there are sex differences in humor processing in the sense that girls and women more strongly activate brain regions sustaining both cognitive and emotional humor components than boys and men. One possible underlying mechanism might be relatively lower reward expectation in females, making them more susceptible to humor effects on reward processing circuits.
We also found evidence for altered humor processing as a function of personality traits in healthy children and adults (e.g., shyness or extraversion), as well as in adults suffering from psychological (e.g. depression and social anxiety disorder) or psychiatric (e.g. autism) disorders. By describing the potentially separable effects of these characteristics on cognitive versus emotional humor components, such findings are of potential clinical relevance as they provide valuable information on conditions involving altered experience of social reward.
Finally, we suggest that our review of the neural basis of humor in humans can also inform theories on the evolutionary significance of humor. In particular, this applies to a theory of humor associated with sexual selection. This theory states that humor may contribute to mate selection choices for women, allowing them to evaluate potential mates on otherwise difficult to discern characteristics like intelligence, social skills and resilience. (For more details, see my previous blog).
While our perspective paper provides valuable insights into the present knowledge of humor processing in humans, it clearly shows there are many outstanding questions that need to be addressed in the future. Our investigations will continue.
Pascal Vrticka, PhD, is a postdoctoral scholar in Stanford’s Center for Interdisciplinary Brain Sciences Research.