References

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Burgdorf, J. & Panksepp J. (2001). Tickling induces reward in adolescent rats. Physiology and Behavior, 72 (1-2), 167-173. doi:10.1016/S0031-9384(00)00411- X

Burgdorf, J. & Panksepp J. (2000). 50-kHZ chirping (laughter?) in response to conditioned and unconditioned tickle-induced reward in rats: effects of social housing and genetic variables. Behavioral Brain Research, 155(1), 25-38. doi: 10.1016/S0166-4328(00)00238-2

Burgdorf, J. & Panksepp J. (2003). “Laughing” rats and the evolutionary antecedents of human joy? Physiology & Behavior 79, 533-547. doi: 10.1016/S0031- 9384(03)00159-8

Budzynski, S. M. (2009). Communication of adult rats by ultrasonic vocalization: biological, sociobiological, and neuroscience approaches. ILAR Journal, 50(1), 43-50. Retrieved from http://dels- old.nas.edu/ilar_n/ilarjournal/50_1/pdfs/v5001Brudzynski.pdf

Cosmic Log (2009, June 4). How animals laugh. Message posted to http://cosmiclog.nbcnews.com/_news/2009/06/04/4351640-how-animals- laugh?lite

Edmonds, M., & Miller, J. (2009, June 4). 10 Different Types of Laughter. Message posted to http://science.howstuffworks.com/environmental/life/inside-the- mind/emotions/5-types-of-laughter.htm

Free Science Lectures. (2007, June 11). Rats laugh when you tickle them. Retrieved from http://youtu.be/j-admRGFVNM

Hofer, M. A. (1996). Multiple regulators of ultrasonic vocalization in the infant rat. Psychoneuroendocrinology 21(2), 203-217. doi:10.1016/0306-4530(95)00042-9

Johnson, K. J. Rat Facts (2012). WereRat. Retrieved October 9, 2012, from http://wererat.net/ratfacts.htm

Panksepp, J. (2003). Can anthropomorphic analysis of separation cries in other animals inform us about the emotional nature of social loss in humans? Psychological Review, 110(2), 376-88. doi: 10.1037/0033-295X.110.2.376

Panksepp, J. (2007). Neuroevolutionary sources of laughter and social joy: modeling primal human laughter in laboratory rats. Behavioral Brain Research, 182(2), 231-244. doi: 10.1016/j.bbr.2007.02.015

Simonet, P., Versteeg D., & Storie, D. Dog-laughter: recorded playback reduces stress related behavior in shelter dogs. Proceedings of the 7th International Conference on Environmental Enrichment. Retrieved from http://www.petalk.org/LaughingDog.pdf

Wynne, C. D. L. (2007). What are animals? Why anthropomorphism is still not a scientific approach to behavior. Comparative Cognition & Behavior Reviews, 2, 125-135. Retrieved from http://psyc.queensu.ca/ccbr/Vol2/Wynne.pdf

Wöhr, M., & Schwarting, R. K. W. (2007). Ultrasonic communication in rats: can playback of 50-kHz calls induce approach behavior? PLoS ONE 2(12): e1365. doi:10.1371/journal.pone.0001365.

Images

Rat pups suckling from Ingiequeen.

Rat with teeth, as well as the pile of rat pups, from The Scientific American.

Laughing rat cartoon from MIT.

Tickled rat from ABC News.

Dopamine circuit drawing from ScienceDirect.

Rat larynx from NCBI.

Dog laughing from DailyInfoPics.

Ape laughing from FindingDulcinea.

Phylogenetic tree relating humans to rats from phyloGif.

Phylogenetic tree of laughter from ScienceDirect.

Header image from The Telegraph.