Category: Human variation

Differences in dyslexia

A fascinating article came out in the Science section of The New York Times: Patterns: Dyslexia as Different as Day and Night, by Eric Nagourney. The article is based on an original research piece by Wai Ting Siok, Zhendong Niu, Zhen Jin, Charles A. Perfetti, and Li Hai Tan, who examined the abnormalities in brain activity associated with dyslexia in Chinese speakers (in comparison to better documented examples of the disorder in English speakers).

The basic result is simple, but intriguing, especially in light of some of the other research we’ve discussed on how brain areas linked to language differ, Two languages, one brain and theory of mind:

The report, which appeared last week in The Proceedings of the National Academy of Sciences, found that changes in the brain that may contribute to dyslexia are different for English speakers and Chinese speakers.
The difference may be explained by the fact that English is an alphabetic language, the researchers said. A reader sees a letter and associates it with a sound. Chinese characters, on the other hand, correspond to syllables and require much more memorization.

In English-speaking individuals, dyslexia shows up in neuroimaging studies as weak activity in left occipitotemporal and temporoparietal regions of the brain. The researchers find out, however, that readers of Chinese with dyslexia have a different anomaly in their brain, perhaps due to the difference between alphabetic and ideographic languages. Children with (from the abstract) ‘impaired reading in logographic Chinese exhibited reduced gray matter volume in a left middle frontal gyrus region,’ an area that had already been found to be active in reading and writing Chinese characters. ‘By contrast, Chinese dyslexics did not show functional or structural (i.e., volumetric gray matter) differences from normal subjects in the more posterior brain systems that have been shown to be abnormal in alphabetic-language dyslexics’: the abstract details.

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Emotional intelligence in training

Although I’m not a real big fan of some of the work on ’emotional intelligence,’ here’s an interesting short video of Daniel Goleman on Karma Tube (a positive, social change video site). As the page explains:

Daniel Goleman, author of Emotional Intelligence, asks why we aren’t more compassionate more of the time. Sharing the results of psychological experiments (and the story of the Santa Cruz Strangler), he explains how we are all born with the capacity for empathy — but we sometimes choose to ignore it.

I’m really not sure what we gain by putting ’emotional’ with ‘intelligence’ except that it does seem to increase the importance of empathy and perceptivity for those who undersell these human capacities. That is, I think the furor of ‘EI’ is in part simply that people who normally don’t get just how crucial interpersonal savvy is suddenly notice it.

Nevertheless, Goleman is a good big picture thinker, and in this piece he points out the malleability of human empathy, a crucial consideration for neuroanthropologists. It’s important to point out training effects on these abilities so that we’re not too prone to considering them permanent ‘personality’ traits.

Identical twins not… err… identical?

Although we’ve been accused of hatin’ on twin studies, I admit that I find twins pretty fascinating, mostly because they attract all kinds of magical thinking, not just within traditional Yoruba cosmology, but also in the West. My favorite pair of twins has to be the ‘Jim twins,’ a pair of identical twins discussed in an article in Time Magazine.

Like many identical twins reared apart, Jim Lewis and Jim Springer found they had been leading eerily similar lives. Separated four weeks after birth in 1940, the Jim twins grew up 45 miles apart in Ohio and were reunited in 1979. Eventually they discovered that both drove the same model blue Chevrolet, chain-smoked Salems, chewed their fingernails and owned dogs named Toy. Each had spent a good deal of time vacationing at the same three-block strip of beach in Florida. More important, when tested for such personality traits as flexibility, self-control and sociability, the twins responded almost exactly alike.

The Jim twins are great; they have given me hours of fun just going over the possible genetic roots for their similarity: ‘Oh my god, we’ve got a shared gene for naming our dogs “Toy” and another one for marrying women named “Linda” and, when that didn’t work out, marrying a second wife called “Betty.”‘ (A similarity that the Time Magazine article doesn’t explore.) I mean, I just can’t stop laughing when I think about how lovers of this sort of data actually think that some sort of gene directs people to go vacation in a particular spot or naming a son either James Alan or James Allan (Ooooh, so close… it must be shared genes!). But I digress… I just love the Jim twins’ story so much (see also Jonathan Marks’ book, What It Means to Be 98% Chimpanzee, where he writes that, ‘In the world of twin studies the unscrupulous and the credulous symbiotically plumb the depths of contemporary pseudoscience.’ He’s way funnier than I am writing about this stuff in pieces like ‘Folk Heredity,’ especially the section on ‘hereditarianism’.)

But now we’ve got an interesting piece from Scientific American, Identical Twins’ Genes Are Not Identical, which explores the possibility that identical twins aren’t perfect genetic copies of each other. As the article reports:

Geneticist Carl Bruder of the University of Alabama at Birmingham, and his colleagues closely compared the genomes of 19 sets of adult identical twins. In some cases, one twin’s DNA differed from the other’s at various points on their genomes. At these sites of genetic divergence, one bore a different number of copies of the same gene, a genetic state called copy number variants.

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Human Biology and Models for Obesity

In reviewing the research and public debates, I have come away startled by the depths of politics and misappraisal about the problem, and the need for human biology to counter this mix of science and morality.  So tonight I’ll write about three problematic things I outlined to my class today, and then show how human biology can provide a useful counter. 

Mind/body and nature/nurture dichotomies run rampant in both public and scholarly discussions of debate.  If it’s not willpower, then it is a biological deficiency.  Genetics causes obesity, or super-size-me environments.  These dichotomies are based on philosophical distinctions that are now centuries old.  They do not match up well with how our bodies, minds, and environments actually work. 

The moralization of fat and the politics of diet produce a tremendous incentive for bias, whether explicit or implicit.  Rhetorical arguments are never really rhetorical in the domain of obesity.  Results are tinged by claims of good and bad, of what’s ideal and what needs to be done.  Since thin-is-in, obesity must be bad, no matter the data; finding that miracle cure, whether it is a diet or surgery or drug, promises huge financial gains, so convenient theories are propped up. 

Suspect science results from both old dichotomies and from the moral politics of obesity.  The moral politics is heightened by the uses of science in establishing authority over a problem, whether it is the government, a medical association, restaurant businesses or soda companies. 

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New neuroscience podcasts and Brazilian racial genomics

Vaughn at Mind Hacks points out several sites with good neurosciences lectures to download on a recent post, Lancet and MNI neuroscience podcasts. The ones from Lancet Neurology can be found here; and the ones from the Montreal Neurological Institute are here. In a post in February, Neurology podcasts – the shocking truth, Vaughn offers still more lectures available online from a number of sources (maybe we should try to do this at Neuroanthropology, especially if we can match Vaughn’s description of one podcast as an ‘excessively thorough lecture given by a voice synthesiser’ — now there’s something for which I can strive!).

On the Lancet Neurology site, there’s a number of good-looking lectures, but many are discussions of the whole volume by editor Helen Frankish. This might be an easy way to get a grip on a wide variety of current research, but they are more likely to be kind of technical for the non-specialist.

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Smell, fear and sensory learning

Blogging on Peer-Reviewed ResearchWen Li, James D. Howard, Todd B. Parrish, and Jay A. Gottfried have a fascinating article in the most recent edition of Science, ‘Aversive Learning Enhances Perceptual and Cortical Discrimination of Indiscriminable Odor Cues.’ The researchers trained subjects to discern between the aroma of chemicals that initially were indistinguishable using electric shocks (!) coupled with one of the two aromas. The research is a great example of perceptual learning, a form of neural enculturation that I think is absolutely essential to understanding cultural difference but little appreciated in anthropology.

Subjects in the experiment were given a test of their ability to discern between very closely related chemicals: ‘On each trial, subjects smelled sets of three bottles (two containing one odorant, the third containing its chiral opposite) and selected the odd stimulus.’ Before the training, subjects selected the odd odor out 33% of the time — no better than random. After the repeated association of one chemical with shocks, subjects’ ability to discriminate the smells improved markedly, showing that negative reinforcement training could ‘enhance perceptual discriminability between initially indistinguishable odors.’ Moreover, the neural representation of the smells changed, as found with fMRI.

From their abstract:

We combined multivariate functional magnetic resonance imaging with olfactory psychophysics to show that initially indistinguishable odor enantiomers (mirror-image molecules) become discriminable after aversive conditioning, paralleling the spatial divergence of ensemble activity patterns in primary olfactory (piriform) cortex. Our findings indicate that aversive learning induces piriform plasticity with corresponding gains in odor enantiomer discrimination, underscoring the capacity of fear conditioning to update perceptual representation of predictive cues, over and above its well-recognized role in the acquisition of conditioned responses. That completely indiscriminable sensations can be transformed into discriminable percepts further accentuates the potency of associative learning to enhance sensory cue perception and support adaptive behavior.

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