Tag: evolutionary psychology

The harmonious ape

August 1, 2009 • 11:48 am

Speaking of animals and dissonance, an upcoming article in the journal Primates investigates the question of whether our closest living relative, the chimp, shows a preference for consonant over dissonant music.  The answer is yes, suggesting that the human preference for consonant music lies in our genes.  But be aware that this result is based on just a single chimp.

Background:  Humans prefer consonant over dissonant music, as consonance “evokes a pleasant feeling.”  The fact that the human preference is seen in infants as young as two days old suggests that this preference is inborn rather than learned.  Animals as distantly related as birds can distinguish between the two types of music, but studies of another primate, the cotton-top tamarin (Saguinus oedipus) showed no preference for consonance.  The authors of this study looked at a closer relative to see if perhaps the trait “preference for consonance” might not only be genetically based, but also have appeared in the primate lineage more recently.

Methods and materials:  The authors studied, over six weeks, a single five-month-old female chimpanzee (Pan troglodytes) named Sakura. She had been reared in a zoo by humans, as her mother had rejected her.  The authors claim that she had never been “exposed to any particular music source such as a radio, TV, or CD player throughout her development. . ”

Sakura was strapped onto a bed with a soft belt, and was forced to listen to either consonant or dissonant music.  There were six sets of computer-generated music, each set consisting of a consonant piece and a nearly-identical dissonant piece, in which some of the notes had been swapped for dissonant ones (see paper for further details).  A string was attached to her right arm (see Fig. 1), and by pulling this string she could affect whether the music stayed the same or changed to the alternative version (i.e., consonant to dissonant or vice versa).  The recorded music began. If the chimp pulled the string within seven seconds, the same music would continue playing for up to two minutes.  If she pulled the string between 7 and 14 seconds, the music would also continue, but with a pause of a few seconds.  If she waited longer than 14 seconds to pull the string, the music would change to the alternative version. Sakura was tested once per week for the six week period.

Chimp

Fig. 1. Sakura in bed, choosing the music that appeals (from original paper).

Results:  The mean duration of consonant music sessions for Sakura was 24.6 seconds, but only 15.9 seconds for the dissonant music. Statistical analysis of the sessions (each including about 10 bouts of each type of music) showed that this difference was significant.  That is, there was a significant preference for the consonant tunes over their dissonant alternatives. When Schoenberg was played, Sakura became very agitated and flung feces at the observers (kidding!)

What it means:  The authors interpret this result as suggesting that “one of the major factors that constitute musical appreciation might not be unique to humans; instead it might be something that we share with our phylogenetically closest relatives.” That is, dissonant tones may affect the nervous systems of chimps and humans in similar ways, and lead to similar subjective sensations.  That seems to be a reasonable conclusion, although of course we need studies where the number of primates exceeds one.

The authors note one potential flaw in the work: suppose that the dissonant music caused the chimp to relax more.  Then she would be less inclined to pull the string when that music was playing, and according to the experimental protocol the music would then change over to the consonant form. This could give the impression that she preferred the consonant over dissonant music as a simple experimental artifact.  The authors say that they consider this possibility “unlikely,” but they didn’t control for it.  One way would be to change the experimental protocol in a separate experiment so that the music would change over when the string was pulled quickly rather than after a longer interval.

One question the authors don’t bring up is whether animals of any sort produce consonant rather than dissonant music.  Do birds, for example, tend to sing consonantly rather than dissonantly?  I am a music tyro and don’t know the answer.  However, the efficacy of animal communication may rest on things other than whether it’s pleasant for them to hear.

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T. Sugimoto, H. Kobayashi, N. Nobuyoshi, Y. Kiriyama, H. Takeshita, T. Nakamura, and K. Hashiya.  2009. Preference for consonant music over dissonant music by an infant chimpanzee. Primates, in press.

Genetic determinism? Not so fast.

June 26, 2009 • 7:27 am

There are several items in the news today relevant to evolutionary psychology.  First, David Brooks, in The New York Times, has an op-ed piece on the excesses of evolutionary psychology.  Apparently “inspired” by a new book by Geoffey Miller, Brooks resists evo-psycho’s exaggerated claims:

Now Miller has published another book, “Spent,” in which he takes evolutionary psychology to the mall. The basic argument is that each of us is born with our own individual level of six big traits: intelligence, openness to new things, conscientiousness, agreeableness, emotional stability and extraversion. These modules are built into humans and other animals (apparently squid can be shy).

We are all narcissists, Miller asserts. We spend much of our lives trying to broadcast our excellence in these traits in order to attract mates. Even if we’re not naturally smart or outgoing, we buy products and brands that give the impression we are.

According to Miller, driving an Acura, Infiniti, Subaru or Volkswagen is a sign of high intelligence. Driving a Cadillac, Chrysler, Ford or Hummer is a sign of low intelligence. Listening to Bjork is a sign of high intelligence, while listening to Lynyrd Skynyrd is a sign of low intelligence. Watching Quentin Tarantino movies is a sign of high openness. He theorizes that teenage girls may cut themselves as a way to demonstrate their ability to withstand infections.

Evolutionary psychology has had a good run. But now there is growing pushback. Sharon Begley has a rollicking, if slightly overdrawn, takedown in the current Newsweek. And “Spent” is a sign that the theory is being used to try to explain more than it can bear.

This critique, along with Sharon Begley’s (see below), is a welcome sign that people won’t credulously accept the excessive claims of evolutionary psychology. Miller, in particular, has made a name (and some bucks) with ludicrous and insupportable claims about the genetic basis of human nature.  Now, Brook’s own critique is not perfect. He says, for example:

The second problem is one evolutionary psychology shares with economics. It’s too individualistic: individuals are born with certain traits, which they seek to maximize in the struggle for survival.

But individuals aren’t formed before they enter society. Individuals are created by social interaction. Our identities are formed by the particular rhythms of maternal attunement, by the shared webs of ideas, symbols and actions that vibrate through us second by second. Shopping isn’t merely a way to broadcast permanent, inborn traits. For some people, it’s also an activity of trying things on in the never-ending process of creating and discovering who they are.

This really says almost nothing, and ignores the fact that humans certainly evolved in a social milieu, and that some of our evolved traits must have been adaptive only in a social milieu.  How else can you explain an inborn facility to learn language?  Brooks would have been better off making the most trenchant critique of evolutionary psychology:  the tendency for many advocates to make speculations completely unsupported by evidence.  Do young girls really cut themselves to demonstrate a resistance to infection? Why isn’t it young men who do the cutting? After all, it’s the men who compete for women, and the “handicap” view of sexual selection posits that ornaments like the peacock’s tail are there to show females that males have the genes or constitution able to deal with (or at least produce) a debilitating but attractive feature.  When it comes to speculations about human behavior, we also have to worry that they could have unintended social consequences. Promoting the notion that self-mutilation might be adaptive may, for example, have the side effect of promoting its spread.

Apropos, Sharon Begley of Newsweek has just published a long critique of evolutionary psychology, a critique that is surprising for a mainline magazine. Begley beings with a critique of Thornhill and Palmer’s “adaptive rape,” hypothesis, which I also attacked in a New Republic article.  Begley then discusses some data that refute evo-psycho’s more popular claims, noting that these refutations get far less press than the original, sensationalistic claims.

Evolutionary psychology is not going quietly. It has had the field to itself, especially in the media, for almost two decades. In large part that was because early critics, led by the late evolutionary biologist Stephen Jay Gould, attacked it with arguments that went over the heads of everyone but about 19 experts in evolutionary theory. It isn’t about to give up that hegemony. Thornhill is adamant that rape is an adaptation, despite Hill’s results from his Ache study. “If a particular trait or behavior is organized to do something,” as he believes rape is, “then it is an adaptation and so was selected for by evolution,” he told me. And in the new book Spent, evolutionary psychologist Geoffrey Miller of the University of New Mexico reasserts the party line, arguing that “males have much more to gain from many acts of intercourse with multiple partners than do females,” and there is a “universal sex difference in human mate choice criteria, with men favoring younger, fertile women, and women favoring older, higher-status, richer men.” . . .

Yet evo psych remains hugely popular in the media and on college campuses, for obvious reasons. It addresses “these very sexy topics,” says Hill. “It’s all about sex and violence,” and has what he calls “an obsession with Pleistocene just-so stories.” And few people—few scientists—know about the empirical data and theoretical arguments that undercut it. “Most scientists are too busy to read studies outside their own narrow field,” he says.

It’s about time something like this was published in a place where people can see it.   Bravo, Ms. Begley!

Speaking of research whose initial lurid claims get far more press than their later refutation, consider human “behavior genes.” Case after case in which researchers claim to have found genes for depression, novelty-seeking, alcoholism, schizophrenia, and the like have later been shown to be nonrepeatable in bigger data sets, or in data from other populations.  But the failures to replicate get far less media attention than do the original claims.  One example this week: a new “meta-analysis” study in the Journal of the American Medical Association that refutes an earlier claim that a gene involved in serotonin transport causes depression.    (See here and here for popular reports about the failure to replicate).  At least in this case, Newsweek (are they on a good science kick?) highlighted the refutation.  There are, naturally, evolutionary hypotheses about why genes for depression may be adaptive; I discuss some of these in WEIT.

All this goes to show that when it comes to assertions about the genetic/evolutionary basis of human behavior, caveat emptor.

Evolutionary psychology: the adaptive significance of semen flavor

April 18, 2009 • 5:42 am

I have long been critical of many evolutionary psychologists for their over-the-top stories, but today I am forced — albeit briefly — to join their ranks. I have thought of a hypothesis that shares all the salient traits of the best ideas of evolutionary psychology: it is brilliant, makes evolutionary sense, and is untestable.

It is the conventional wisdom in human sexuality that semen tastes bad. Anyone with minimal sexual experience knows that although many women will perform fellatio on their partners, most bridle at the thought of swallowing the ejaculate. Its flavor is frequently characterized as revoltingly bitter or salty. The “swallow or spit” dilemma faces any woman who performs such an act, and whose partner regards swallowing as a gesture of love.

The universal distastefulness of semen is attested by the many internet sites that give advice about how to improve the taste of one’s ejaculate, for example, here, here, and here.

To get a better scientific handle on this idea, I took a poll, asking a woman friend, Dr. Fawzia Rasheed, to canvass her female acquaintances about their willingness to swallow after the act of fellatio. Twenty-four women were asked this question:

Sperm…would you spit or swallow? In other words, can you abide by or do you hate the taste?

There were sixteen responses, many including pungent asides that I cannot repeat on a family-oriented website. One answer was a non-response (“I should be so lucky”). The other fifteen included eleven “spits” and four “swallows”. But among the latter, two women commented that they did not like the taste: one, in fact, swallowed to get rid of the flavor as quickly as possible. Two others said “swallow” but did not comment on whether they enjoyed it. Therefore, 13/15, or 87% of informative respondents could not abide the taste of semen.

This near-unanimous response to a random poll demands an evolutionary explanation. Why does semen taste so foul? One answer, of course, is that the chemicals necessary to make an ejaculate effective have the side effect of tasting bad. Semen is only about 5% sperm, with the remainder of the fluid consisting of a complex mixture of compounds from the prostate gland and seminal vesicle. These compounds include sugars such as lactose [CORRECTION: fructose; see below ] (to provide energy for the swimming sperm), enzymes, amino acids, zinc, hormones, and various amines to counteract the acidic environment of the vagina (these are said to give sperm its characteristic smell and flavor). Some of these amines have the names putrescine and cadaverine, which give an idea of how they smell. The function of some of the compounds is unknown; they may help overcome female immune defenses or even function in male-male sperm competition when females are multiply inseminated.

But this proximate answer will not satisfy the diligent evolutionary psychologist. After all, natural selection could presumably add some sugars or good-tasting stuff to semen if it were advantageous to do so. Why does it not do so?

A moment’s reflection gives the answer.

Natural selection maintains the repugnant taste of semen so that a man’s sperm will wind up in the appropriate place: the vagina and not the stomach. So long as sperm tastes bad, women will not be tempted to swallow it, but will turn their male partner towards conventional intercourse, which of course is the only act that will produce children. In other words, any male with good-tasting sperm would have fewer offspring than his competitors. A man whose sperm tasted like honey would probably not have any children at all.

I can think of only two ways to test this hypothesis, both of them impractical or impossible:

1. If women gave birth through their stomachs, semen would taste great

2. Those males with genes giving them better-tasting semen will leave fewer offspring than other males.

This theory is offered as a modest proposal, only partly (excuse me) tongue in cheek. It may even be true.

Notes added post facto: Although light-hearted, the post is somewhat serious; it’s the kind of interesting speculation that evolutionists indulge in over a few beers. And everything in the post is true, including the survey of women.

And note to T.R. Gregory: I don’t think this idea is refuted by finding, say, primate species that don’t have oral sex but do have similar compounds in the semen. The whole idea rests on those compounds TASTING BAD to females, and we’d need to know something about the taste reactions of females in these other primates. The evolution, after all, might have been in the female taste receptors rather than in the semen.

Finally, apologies to readers who find the subject distasteful.

Review of WEIT in Wall Street Journal

January 29, 2009 • 9:38 am

A very nice review of WEIT appeared today in the Wall Street Journal.  It was written by the distinguished philosopher Philip Kitcher, who has written extensively on evolution, creationism, and evolutionary psychology.  I highly recommend his recent book, Living with Darwin: Evolution, Design, and the Future of Faith, which not only dismantles intelligent design, but deals with the thorny problem of how nonreligious people can find the same kind of solace and social networking that is provided by religion. Philip also wrote what I consider the definitive critique of evolutionary psychology (then called “sociobiology”): Vaulting Ambition: Sociobiology and the Quest for Human Nature.  Finally, his avocation is James Joyce, and he’s just penned an introduction for the general reader to Finnegans Wake: Joyce’s Kaleidoscope: An Invitation to Finnegans Wake, an accomplishment which I can regard only with astonishment.