Humans laugh for all kinds of reasons. When someone tells a funny joke or when we are experiencing the emotions of joy, surprise, amusement, nervousness, or fear we may laugh. It turns out that animals also produce laughter, although for different reasons. Two articles I read explored the "chirp of joy" made by juvenile rats when they are tickled, and the laughter-like vocalization of the spotted hyena.
A study on rats found that when juveniles were tickled they produce 50kHz ultrasonic "chirps of joy". Researcher Jaak Panksepp found that the young rats were most ticklish at the nape, which is the focus of pinning and other play behavior between rats. The most "ticklish" individuals- the ones the emitted the most chirps- were also found to be the most naturally playful. Tickling also promoted bonding between rats and people, and between rats. Panksepp suggests that this response to tickling in rats is akin to the response to tickling in human infants.
Spotted Hyenas (crocuta crocuta) do not laugh because of joy or amusement, but as a way to express their social standing- according to researchers Mathevon et al. The characteristic cackling sound is made most frequently during a social conflict or a feeding session. The researchers determined that each hyena produces a unique "laugh" that encodes information about their age and rank. Hyenas with high-pitched, variable cackles were lower-ranking individuals, and hyenas with lower, monotone cackles were higher-ranking.
I think what these two articles have in common is that they show how "laughter" (chirps or laughter-like vocalizations) in the animal kingdom is distinct from the "sense of humor" in humans. If anyone has an example of animals with a sense of humor that would be really interesting!
If you are interested in reading the articles they can be found here: http://scientificamerican.com/article.cfm?id=laughing-rats-and-ticklish-gorillas-2010-08-03
http://www.livescience.com/animals/090905-hyena-giggle.html
Posted by Alex Sprague (3)
Edit:
Thank you all for the comments!
I didn’t know that licking in mice decreases the expression of a stress gene. That is really interesting and it seems like the same thing could apply to tickling in rats. In some way the tickling might change expression of a gene, or just increase the levels of certain hormones in the rat which make it friendlier and happier. The article only talked about the results of tickling, but didn’t provide a mechanism for the behavior.
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Pretty interesting article. I've always wondered if other animals have the capability to laugh or experience humor. The article about the mice is the most interesting to me. The fact that tickling between human and mice can lead to a developed relationship between the two. Additionally i wonder if there has been any other research done on how tickling is experienced in other species.
ReplyDeletePatrick Salome
In genetics, we talked about how, in mice, a mother licking her pups will decrease expression of a stress gene, while absence of licking will increase expression, resulting in more anxiety-prone mice. Because laughter is stress-relieving, I wonder if tickling and play behavior in rats has some of the same effects. That is, if rats that have more time to play (in the absence of predators or other environmental pressures) will have less stress.
ReplyDelete-Jane de Verges
Tickling to promote bonding? Really interesting idea. I never knew that the "laugh" a Hyena made was akin to its social status. It really shows the variety of types of communication there are.
ReplyDeleteAlberto Suarez
It’s really interesting that laughter can have many functions depending on the species. In the movie we watched in class, it said that some behaviors are conserved across development, but have different meanings because the context and receivers change. We learned in a psychology class that male rats will “sing” an ultrasonic song to the females during mating. I wonder if these calls and the laughing are somehow related?
ReplyDeletePosted by Katie Kalutkiewicz