Thursday, December 3, 2009

Recent evolution of complex behavior

I once knew an African student who told me that his language had no words for “good” or “evil”. When the missionaries translated their materials into his language, they had to write “Jesus is beautiful” instead of “Jesus is good.”

This sort of semantic evolution has occurred in all human languages. People have expressed new concepts by recycling older ones. Typically, these older concepts refer to primary sensations that are largely hardwired, i.e., ‘beautiful’, ‘cold’, ‘hot’, and so on.

Interestingly, it looks as if some of this hardwiring is being reused when we imagine evolutionarily recent concepts. For instance, when we recognize someone as friendly, we use neural pathways that are associated with the recognition of warmth.

During the autumn of 2006, a series of volunteers arrived at Yale University's psychology building. Each was greeted in the lobby by a researcher, who accompanied them up to the fourth floor. In the elevator, the researcher casually asked the volunteer to hold the drink she was carrying while she noted down their name. The subjects did not know it, but the experiment began the moment they took the cup.Once in the lab, the 40 or so volunteers read a description of a fictitious person and then answered questions about the character. Those who had held an iced coffee, rather than a hot one, rated the imaginary figure as less warm and friendly, even though eachvolunteer had read the same description. Answers to other questions about the figure, such as whether the character appeared honest, were unaffected by the type of drink. (Williams & Bargh, 2008).

Similarly, we have developed the ability to form moral judgments by building upon a mental algorithm that serves to judge cleanliness:

In one recent study, Simone Schnall at the University of Plymouth, UK, and colleagues showed half their volunteers a neutral film and the other half the toilet scene from the film Trainspotting. (The uninitiated need only use their imagination here: the clip features what is described as the "worst toilet in Scotland".) Those who viewed the Trainspotting clip subsequently made more severe judgements about unethical acts such as cannibalism than volunteers who had viewed the neutral scene. Exposing subjects to a fart smell and placing them in a filthy room had a similar effect (Schnall et al., 2008).

Chen-Bo Zhong of the University of Toronto in Canada and Katie Liljenquist, now at Brigham Young University in Provo, Utah, asked volunteers to read a first-person account of either an ethical act or an act of sabotage. They then had to rate the desirability of various household objects, including soap, toothpaste, CD cases and chocolate bars. Those who had read the sabotage story showed a greater preference for the cleaning products than those who had not.

A self-perception of physical cleanliness thus seems linked to one of moral cleanliness. Moreover, like Pontius Pilate, the mere act of washing your hands reduces feelings of moral responsibility.

… In another part of their study, Zhong's team asked volunteers to recall an unethical deed from their past. Under the guise of a health and safety precaution, he then gave half the subjects antiseptic wipes to clean their hands. The participants were then asked if they would take part in another experiment, this time to help out a desperate graduate student. Only 40 per cent of the subjects who had cleaned their hands volunteered, compared with almost three-quarters of those who hadn't. (Zhong & Liljenquist, 2006)

These studies suggest an answer to a question that has bothered me. How is that complex and relatively recent social behaviors often have moderate to high heritabilities? Surely such hardwiring would have taken an impossibly long time to evolve? Just think of all the genes involved…

Well, the answer is surprisingly simple. Natural selection has simply altered a hardwired algorithm that already exists. There’s no need to build it all from scratch. You just jerry-rig what you already have.


Mangan’s Miscellany is back!! In fact, he's back at his old address ( and at a new one (


Giles, J. (2009). Icy stares and dirty minds: Hitch-hiking emotions, New Scientist 2725:* 15 September 2009

Schnall, S., J. Haidt, G.L. Clore, A.H. Jordan. (2008).
Disgust as embodied moral judgment, Personality and Social Psychology Bulletin, 34, 1096-1109.

Williams, L.E. & J.A. Bargh. (2008).
Experiencing physical warmth promotes interpersonal warmth, Science, 322, 606-607

Zhong, C.B. & K. Liljenquist, K. (2006). Washing away your sins: Threatened moralityand physical cleansing, Science, 313, 1451-1452.


Ken said...

"A self-perception of physical cleanliness thus seems linked to one of moral cleanliness"

That would be the reason why military training puts a lot of emphasis on cleanliness - to inculcate a certain state of mind.

A lot of how we perceive things seems to be determined by the interaction of various hardwired algorithms, each with dedicated neurons. Social interaction is a lot more mechanistic than one would like to think.

Anonymous said...

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