It’s been known for awhile that people tend to feel greater sexual attraction to those whose major histocompatibility complex (MHC) is different from their own than to those whose MHC is similar. The MHC is an area of the genome that has to do with the immune system; people appear to sense differences in MHC at least partly by smell. Maybe this helps people avoid mating with someone who is genetically similar; it’s also likely that children of parents with dissimilar MHC will have stronger immune systems. Perhaps these MHC differences lie behind some of the romantic chemistry that a couple feels (or lacks). A new study investigated the sex lives of couples, looking for correlations between sexual behaviors and genetic similarity. In a nutshell, genetic similarity is linked to less spark between partners and a greater chance of the woman finding another sexual partner, particularly during the fertile phase of her cycle. New Scientist has a brief article and also this longer one.
One more bit of news about the debate over the fossils found in Indonesia (Homo floresiensis or otherwise): the site where the bones were found is being re-opened for further exploration. Perhaps more samples will provide evidence that will end the debate over whether the bones are from a new species or from a microcephalic Homo sapiens. There’s a brief news item at Scientific American.
It’s easy to infer personality traits from a person’s face, and novelists sometimes will give a character facial features that supposedly indicate what kind of person the character is. Whether there really is a correlation between how you look and how you act is unclear, but some recent research conducted by a social psychologist at the University of Michigan offers some interesting new data. Undergrads, male and female, were shown images of a variety of male faces doctored to look more or less masculine. The subjects had to answer questions about the characteristics of the men and choose which of them they would prefer for certain things (as a friend, as a date, etc.). They tended to rate the owners of the more masculine faces as being more likely to go after someone else’s girlfriend, two-time their own lovers, tangle with the boss, or get into fights, whereas the owners of the less masculine faces were judged more likely to make good parents or husbands and be responsible about going to work. The interesting thing is that there may be some link between how masculine a guy’s face looks and how he behaves, because facial features are influenced by testosterone levels early in life, and testosterone levels are in turn linked to rates of divorce, infidelity, and violent behavior. (I’m assuming that is testosterone levels during adulthood, although the article is not clear, and I’m not sure what relationship there is between developmental and adult levels of testosterone.) Men and women subjects tended to react to the high-T or low-T faces in ways that would seem to enhance their own ability to successfully reproduce, so whether or not there is any meaningful link between looks and behavior, people certainly seem to act as though there is.
1/31/07 I meant to add a link: here’s the article from Science Daily.
In 2003, some unusual hominid bones were discovered on the Indonesian island of Flores. The short, small-headed, so-called “hobbit” specimen sparked an ongoing debate about whether the bones belonged to a physically deformed (perhaps microcephalic, or unusually small-brained) modern human or to a different species, dubbed Homo floresiensis. In August of 2006, an international team published the results of its investigations, which indicated that the bones were not those of a new species. However, the latest news is that Dean Falk’s team at Florida State, which first identified the bones as those of a new species in April 2005, has completed further studies of the skull that support their earlier conclusion, contrary to the other team’s August 2006 results. Casts of the skull reveal details of brain anatomy and show that the ancient hominid’s brain resembles that of a modern human rather than a microcephalic brain, although it also has unique features that would justify its designation as a new species. This press release gives more details. This evidently settles the question enough for Falk that she says it’s time to start working on other questions about Homo floresiensis, but I don’t know if we’ve really heard the last of the debate.
In this essay from Edge, neuroscientist V.S. Ramachandran discusses how the evolution of mirror neurons might have contributed to our sense of self. He proposes that mirror neurons developed before conscious awareness of self did. Having developed this nifty ability to read the minds of others and figure out what they were thinking (and perhaps anticipate how they might behave), could we have then turned this ability on ourselves and learned to figure out what we ourselves were thinking, thus developing a sense of a self that we could observe? He notes that if this is the case, the mirror neurons might have been necessary but were not sufficient, because other primates have them but don’t have the kind of self-awareness that we do. I would like to see how his proposal could be tested, and I’m also curious about how it relates to the fact that in some ways we don’t really know ourselves all that well (of course, we don’t always know other people very well either). I’m thinking in particular of Timothy Wilson’s book Strangers to ourselves: The adaptive unconscious, which describes the ways that, for a variety of reasons, our brains keep a good deal of their workings away from conscious awareness, so that what we know about ourselves is sometimes not as reliable as what others could tell us about ourselves. (I think this is related to the “Easy Question” about consciousness that Steven Pinker mentions in the essay I linked to yesterday: “to distinguish conscious from unconscious mental computation, identify its correlates in the brain and explain why it evolved.”)
And along those lines, here is a discussion on Seed Magazine’s site between evolutionary biologist Robert Trivers and linguist Noam Chomsky about deception, including self-deception. It’s a mix of political and other examples of group and self deception (including the mental gyrations of the Bush administration in the lead-up to the war in Iraq), and some data from psychology about how people describe themselves and others (tending to flatter themselves, in general, and downplay the virtues and overemphasize the failings of the other guy).
Time has published a bunch of stuff on brain science lately. in particular an essay by Steven Pinker on consciousness. He gives a nice overview of some of the problems and the current progress in studies of consciousness, and then goes on to talk about some of the ramifications of the belief that consciousness arises solely out of physiological activity in the brain (which entails the loss of belief in the concept of the immortal soul). He argues, not surprisingly, that “the biology of consciousness offers a sounder basis for morality than the unprovable dogma of an immortal soul.” He doesn’t have much room to elaborate on this, but I am in entire agreement with his closing sentence: “I would argue that nothing gives life more purpose than the realization that every moment of consciousness is a precious and fragile gift.”
There are also links to more articles about brain science, most notably one by Sharon Begley about how the brain rewires itself, about how mental activity can change the physical structure of the brain, and how we retain neuroplasticity (the ability of the brain to change, either in response to external stimuli or in response to our own thoughts) even into old age.
I heard a few stories on NPR this morning on Thinking Meat-type topics. The first two were about possible new treatments for depression. Transcranial magnetic stimulation (TMS), which uses magnetic pulses to stimulate specific parts of the brain, is being investigated as a treatment for those whose depression is resistant to antidepressants and psychotherapy; NPR has a brief blurb with a link to the audio story. Another treatment for tough cases of depression, already approved by the FDA and currently being reviewed, applies electrical stimulation to the vagus nerve; the NPR story describes the disagreement among those who treat depression about the benefits of this treatment. Vagus nerve stimulation is much more invasive than TMS because a battery and an electrode need to be surgically implanted.
TMS, in addition to its potential for treating depression, is also a very useful tool for neuroscientists because it allows them to precisely target a particular part of the brain for stimulation, which essentially gives them the ability to briefly and apparently more or less harmlessly turn off a part of the brain to see what falters in its absence. One way we’ve learned about what different parts of the brain do is by observing people with damage to specific areas of the brain and seeing what mental tasks they have problems with; I gather that TMS allows for a similar sort of detective work on undamaged people. I’ve blogged a few things about TMS (e.g., an entry about the use of TMS to mimic a condition called semantic dementia, an inability to connect words and concepts). The NPR article describes some of the uses that researchers are finding for TMS.
This essay from Robert Solomon in the Chronicle of Higher Education argues against the popular perception of existentialism as a pessimistic philosophy (a perception that has long mystified me) and in favor of existentialism as full of hope and possibility. I don’t really understand how working to find your own meaning in life is supposed to be so pointless compared to believing that everything is in the hands of a deity; to me it seems just the opposite, that creating your own meaning is much more rewarding than accepting that someone else, even a deity, decided it all long ago.
Robert Solomon was a philosophy professor at the University of Texas, and he wrote, among other things, a book called Spirituality for the Skeptic: The Thoughtful Love of Life; what I’ve read about it sounds promising and it’s in the stack of books in my bedroom awaiting my attention. It sounds like it’s in line with my own beliefs about how the lack of conventional religion does not need to mean a lack of meaning, values, or morality. What makes the Chronicle piece a bit poignant is that Solomon died on January 2 while traveling (he was 64; his death was due partly to a congenital heart condition). I’m glad he left at least some of his thoughts behind in his books.