Hierarchies among Equals–Origins of Pecking Orders

Scientific American Hierarchies among Equals–Origins of Pecking Orders Drop two adult rats of the same sex into a cage, and it’s a near certainty that the bigger rat, even if only slightly bigger, will dominate from the first minutes. But what happens if you take several freshly weaned rats, all of equal size and from good homes, and put them together? A hierarchy nonetheless emerges, according to a new experiment, but the determining factors remain a mystery. These factors–in good news for humans at the low end of the social ladder–may be mutable.
Darlene Francis, a psychologist at the University of California, Berkeley, placed 80 newly weaned rats in cages of four, with cage mates matched for size, activity level and early life environment. To Francis’s amazement, it took weeks–until the rats were well past puberty–for a social hierarchy to evolve (as indicated by which mouse got first dibs at food and water, among other measures). Perhaps more surprising was that the hierarchies were not determined by the differences in weight, activity or size that had developed among the maturing quartets–or by anything else Francis could identify.
 [More] …………………………………………………… http://rss.sciam.com/click.phdo?i=72b1bf69630fbb11f8607f1bff63801e


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