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The Physicians Committee



Beyond Animal Research

By Jonathan Balcombe, Ph.D.
October 2004

The Misunderstood Rat

Rats are one of the world’s least understood creatures. Stigmatized as filthy “pests” for centuries, these inquisitive opportunists are actually naturally sociable and make excellent companions. New scientific studies show that there is more to rats than laboratory supply companies would have us believe.

Rats love to play, especially when young. During play, rats’ brains release large amounts of dopamine and opiates (in people, these chemicals are associated with pleasure and excitement).1 They chirp with apparent joy both during play and in anticipation of it,2 and one distinguished neuroscientist believes these chirps are a rat version of laughter.3

Rats are also tactile. They will nip gently to solicit tickles and strokes from trusted human companions.2 In a carefully controlled laboratory study at Bowling Green State University, rats accustomed to tickling ran to the hand four times as quickly as did petted rats and made seven times more chirps. The difference increased over the five-day period, suggesting a growing enthusiasm for being tickled.4 In the same study, each rat was presented with two metal bars, only one of which offered a tickling reward when pressed. The animals pressed the tickle bar repeatedly, but almost never pressed the other bar.4

Rats also play fair. When researchers at the University of Lethbridge analyzed video footage of playing rats, they found that individuals assess and monitor one another, then fine-tune their own behavior to maintain the play mood.5 Playing rats restrain themselves when they know their actions would cause pain to another individual.6 The cooperation and fairness required of play may form the basis for a sense of right and wrong and the rudiments of moral behavior.7

Like humans, rats appreciate variety in their food. A 2003 study found that rats (and hamsters) favored new foods following several days’ exposure to a single food.8 Rats will also enter a deadly cold room to retrieve highly palatable food, even though their regular chow (which is dry and monotonous) is available in their cozy nests.9 This is a rodent version of shunning the fruit bowl and dashing out for donuts on a wintry night.

These studies show that rats are not as different from us as some might think. Not only do they try to avoid painful or stressful situations, they seek out pleasurable ones. They look forward to a good game, they obey rat rules of social conduct, and they have preferences. These traits constitute more reasons why these sensitive, intelligent animals should not be subjected to harmful experiments.

References
1 Panksepp, J. 1998. Affective Neuroscience. Oxford University Press.
2 Knutson B, Burgdorf J, Panksepp J. Anticipation of play elicits high-frequency ultrasonic vocalizations in young rats. Journal of Comparative Psychology. 1998;112:65-73.
3 Panksepp J, Burgdorf J. “Laughing” rats and the evolutionary antecedents of human joy? Physiology & Behavior. 2003;79:533-547.
4 Burgdorf J, Panksepp J. Tickling induces reward in adolescent rats. Physiology & Behavior. 2001;72:167-173.
5 Pellis S. 2002. Keeping in touch: Play fighting and social knowledge. In Bekoff M, Allen C, and Burghardt GM (eds.) 2002. The Cognitive Animal Cambridge, Mass: MIT Press.
6 Church F. Emotional reactions of rats to the pain of others. Journal of Comparative and Physiological Psychology. 1959;52:132-134.
7 Bekoff, M. Wild justice, cooperation, and fair play: Minding manners, being nice, and feeling good. In R. Sussman and A. Chapman (eds.) The Origins and Nature of Sociality. Aldine, Chicago. pp. 53-79.
8 Galef BG Jr, Whiskin EE. Preference for novel flavors in adult Norway rats (Rattus norvegicus). Journal of Comparative Psychology. 2003;117:96-100.
9 Phillips H. The pleasure seekers. New Scientist. 2003;11:36-40.

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