We like our presidents tall, it seems. And now researchers think they know why, saying leftover caveman instincts draw us toward strong and mighty (or tall) leaders who we view as able to protect us.


"Some traits and instincts that may have been acquired through evolution continue to manifest themselves in modern life, seemingly irrationally," study researcher Gregg R. Murray of Texas Tech University said in a statement, adding that our fear of snakes, for instance, likely evolved from a time when snakes were a common threat. [Top 10 Phobias Explained]


"We believe similar traits exist in politics," he said.


Murray, along with Texas Tech graduate student J. David Schmitz, credited the "presidential height index" — a popular observation that taller candidates have won 58 percent of U.S. presidential elections between 1789 and 2008 — as piquing their interest in the role that height plays in leader selection.


"Culture and environment alone cannot explain how a preference for taller leaders is a near-universal trait we see in different cultures today, as well as in societies ranging from ancient Mayans, to pre-classical Greeks and even animals," Schmitz said. For instance, past research based on skeletal measurements collected from pre-classical Greek and ancient Mayan excavations suggests that "political control" was associated with greater physical stature, the researchers write in the Oct. 18 issue of the journal Social Science Quarterly. And studies on animals ranging from chimpanzees and gorillas to African elephants and even some birds suggest height can serve as a cue of an opponent's strength and power.


Tall presidents

The researchers theorized that evolutionary psychology, or the study of universal human behaviors related to psychological mechanisms that evolved based on ancient humans' interactions with their physical and social environments, influenced the development of this height preference for political leaders.


To test their theory, the authors asked 467 U.S. and international students from both public and private schools in the United States to describe and draw a "typical citizen" and an "ideal national leader." They were then asked to draw the citizen and leader meeting each other. The findings showed that 64 percent of the participants drew the leader as taller than the citizen.


In a second study, the researchers asked participants to complete a questionnaire about their height and perceptions of their own leadership characteristics. For example, the participants rated how likely they would be to run for an elected position in an organization on a four-point scale. The results showed that the taller participants were more likely to think of themselves as capable leaders and were more likely to express an interest in pursuing a leadership position.


The findings suggest that humans' preference for tall leaders is likely an evolved psychological trait that is independent of any cultural conditioning, the researchers said. They also stated that individuals with a greater physical stature are more likely to view themselves as qualified to be a leader, and as a result of this increased sense of efficacy, are more likely to pursue a leadership position.


"So while at 6 feet 1 inch, Barack Obama towered over the 5-foot-8-inch John McCain in 2008, perhaps he’ll meet his physical equal in one of the 'big man' governors in the 6-foot-1-inch Rick Perry or the 6-foot-2-inch Mitt Romney in November 2012," Murray said.


Caveman instincts?

Murray said he expects some scientists will be skeptical about the interpretation of the results, for one, because proving a theory in the social sciences is tricky. "We don’t 'prove' things in the social sciences, we present evidence in support of our arguments then look for or do other research to see if we get results that confirm or disconfirm our findings," he told LiveScience.


In addition, some reject evolutionary psychology as an explanation for modern phenomena. "I think mostly because they have not had full exposure to the arguments and evidence [of evolutionary psychology]," Murray said.


Murray's team has ruled out other explanations for our preference of tall leaders, he said, including a cultural reason, such as the possibility that our society is biased against shorter people. The researchers accounted for this idea, finding the phenomenon happens in nonhuman animals, across cultures and in pre-modern human cultures.


Past research has also suggested humans have retained our caveman instincts. A study published in 2007 in the journal Proceedings of the National Academy of Sciences revealed that modern humans are still experts at spotting predators and prey, despite the developed world's safe suburbs and indoor lifestyle.


You can follow LiveScience writer Remy Melina on Twitter @remymelina. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.


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