A new theoretical tool called life history theory offers an answerOliver Sng, Steven Neuberg, Michael Varnum, Douglas Kenrick report: You may be thinking: yes—living under crowded conditions surely drives people crazy. And the reason why may be traced back to some unfortunate rats. In the 1960s, the ethologist John Calhoun wanted to see how overcrowding would influence social behavior in rats. He placed rats in a confined space and allowed them to multiply with relatively little control (Calhoun, 1962). The results looked like scenes out of a horror movie: cannibalism, dead infants, and complete social withdrawal, to name a few.
[Also see - Takeshita Dori Street Panic]Calhoun’s rats captured public imagination and inspired a surge of research on the psychological effects of density in our own species. Some studies found that people living in crowded environments indeed showed a variety of social pathologies, just like Calhoun’s rats. But other studies did not. Reviews of the early research concluded that popular fears about overcrowding may be unfounded (Lawrence, 1974). Now, half a century has passed, and the world population has doubled. On the other hand, research on the psychological effects of density has all but disappeared. We revisit this old topic in our recent paper, this time with a new theoretical tool—life history theory. Life history theory is a theory about how all animals allocate their limited time and energy across life’s tasks, such as growing, mating, and parenting. And aspects of the environment shape these allocation choices (Ellis, Figueredo, Brumbach & Schlomer, 2009; Del Giudice, Gangestad & Kaplan, 2016). What does this have to do with density? One of life history theory’s earliest ideas was that environments of low density—where there are few individuals around—would favor organisms that adopt a “fast” life history strategy. This strategy focuses on quick reproduction, and having many offspring but with little investment in each. Put simply, this strategy is focused on the present and prioritizes “quantity over quality”.
But things get different when the environment gets crowded, and there is strong social competition for resources and territory. To successfully compete, individuals now need to spend more time and energy building their own abilities. This often leads to a delay in reproduction. In a dense environment, one’s offspring also face greater social competition. Hence, it may be more adaptive to focus time and energy on just a few offspring (to increase their abilities and competitiveness), instead of spreading resources over many offspring. … (read more)
Source: Scientific American