杏吧原创

WHAT is the connection between Jonathan the lovesick baboon and an admin assistant called Paul? For starters, they both appear in Robert Sapolsky鈥檚 new book, Monkeyluv, a collection of essays about human (and other primate) behaviour and biology. Sapolsky is a behavioural biologist, and very broad-ranging. Most of these essays have been published before, but he has updated them and most are compelling. His spirit of intellectual adventuring is infectious, and thus I found myself looking for deeper links between some of the disparate theories and individuals he discusses 鈥� like Jonathan and Paul, for example.

Let鈥檚 start with Paul. He鈥檚 a fresh-faced young temp whose eclectic taste in music gets 40-something Sapolsky wondering why the soundtrack to his own life has shrunk to a couple of Mahler symphonies and a trusted tape of Bob Marley鈥檚 greatest hits. In typical Sapolsky style, he takes the idea and runs with it. He wants to know at what age people become closed to new experiences such as a novel genre of music, raw fish with horseradish, or having a stud put through their tongue. He calls a bunch of radio stations, then sushi bars, and finally 35 body-piercing parlours. His conclusions 鈥� 35 for music, 39 for food and 23 for body decorations 鈥� make depressing reading for anyone contemplating a midlife crisis. It seems that our taste for adventure is one of the first casualties of ageing.

Why should this be? Sapolsky considers four explanations. First, as our lives move deeper into a rut, so too does our thinking. Second, eminence breeds reactionary attitudes as we try to defend our own ideas against those of upstarts. Third, identifying with your peer group is simply a facet of the more general human tendency to overvalue whatever group we are part of. Finally, as we age, we crave familiarity as a comforting affirmation of our own continuing existence. All these have their merits, but there must be more to it. And this is where Jonathan the lovelorn baboon comes in.

Jonathan, a gangly young nobody, is smitten by the lovely, aristocratic Rebecca. He spends his days loping around the savannah after her in the vain hope of intimacy. She does her best to ignore him, offering him only the occasional opportunity to groom her. The question here is, given Jonathan鈥檚 abject failure to woo Rebecca, why does he persist?

Sapolsky finds the answer in 鈥渢he pleasure of maybe鈥�. To cut a long story short, experiments show that when rats anticipate a reward, the dopaminergic pathway in the frontal cortex is activated, giving them the equivalent of a shot of cocaine straight to the brain. But here鈥檚 the clincher: when the chance of getting that reward is not a sure-fire thing but only a possibility, the activation happens twice, first in anticipation, then when the reward is due. What鈥檚 more, the total amount of dopamine released is highest when uncertainty is greatest.

鈥淎t what age do people become closed to new types of music?鈥�

Sapolsky says this explains Jonathan鈥檚 tenacity, and why gambling is so addictive, but it seems to me there is a connection here with Paul鈥檚 novelty-seeking. Does he do it for the thrill of not knowing whether he鈥檒l like what he finds? As Sapolsky points out elsewhere in the book, if you really want to know what motivates humans to behave in certain ways, you need to look for 鈥減roximate causes鈥�. For example, we don鈥檛 have sex to proliferate our genes; we do it because it feels good. It looks like the same can be said for trying new stuff.

Why, then, does our appetite for this brand of thrill-seeking drop off as we age. New brain-imaging research offers an inkling of an explanation: older brains often appear more active than younger ones, suggesting that signals such as the pleasure response to 鈥渕aybe鈥� get diluted. Still, if there鈥檚 one overarching message in Monkeyluv, it is that when it comes to understanding human behaviour, the answer is never simple. Or, to distil the essence of the book鈥檚 three sections: not by genes alone; always remember that the mind is embodied; and society maketh the (wo)man.