Category: Human variation

‘Giant sleep machines’ and the brain

I stumbled across this article in the Discover website, entitled How To Sleep Like a Hunter-Gatherer. Quite a bit of the piece is clearly based on a discussion with anthropologist Carol Worthman, director of the Laboratory for Comparative Human Biology at Emory University. The article basically considers some of the variation in human sleep patterns, pointing out how rare and extreme American sleeping behaviors are, especially the extreme quiet, isolation, and uninterrupted, single-shot way that we get out eight hours.

I’m struck by this for a number of reasons; Worthman points out how sleep patterns would be different for people living communally, for foraging groups living in less isolation from the environment, and for folks living in very loud cities (she draws on Cairo, where people also sleep twice during the day and often share sleeping space with other people). The implications are intriguing, as my former colleague Jim McKenna has pointed out in his discussions of co-sleeping.

But I’m also struck by the possibility that the ‘American’ pattern she describes (which is likely also restricted — for example, what about those working night shifts…), might fundamentally affect patterns of alertness, body metabolism, memory, ability to maintain attention, and a host of other factors.

Moving to the country has made me more aware of this because I sleep much less than my wife, and I tend not to be ready to go to sleep when she’s nodding off on the couch after dinner. At night, when everyone else is asleep and I’m working, doing dishes, or writing blog posts, the noise is extraordinary. Between crickets and frogs, the noise level is constantly equivalent to a party on the neighbors’ farm. It’s taken some getting used to. I haven’t yet noticed a change in my sleep patterns, but I suspect that the variation Worthman describes likely has significant affects on the human brain. It’s one of those mechanisms that I’m interested in: it’s ‘cultural’ in the sense that it’s socially-based variation, but it’s largely not conscious, non-semantic, and behavioral, something that most current theories of culture don’t handle very well. Anyway, I don’t have much intelligent to say about the piece — maybe I will after I get some sleep. (I know, that was cheap, but I do want to go to bed, and it’s all I’ve got.)

Poverty Poisons the Brain

Paul Krugman writes today that “Poverty Is Poison,” building off an article from the Financial Times that discussed last Friday’s session, “Poverty and Brain Development” at the American Association for the Advancement of Science.  Krugman writes: 

As the article explained, neuroscientists have found that “many children growing up in very poor families with low social status experience unhealthy levels of stress hormones, which impair their neural development.” The effect is to impair language development and memory — and hence the ability to escape poverty — for the rest of the child’s life. So now we have another, even more compelling reason to be ashamed about America’s record of failing to fight poverty.

The Financial Times article, “Poverty mars formation of infant brains,” provides some more detail about the impact of poverty through stress, inadequate nutrition and exposure to environmental toxins: “Studies by several US universities have revealed the pervasive harm done to the brain, particularly between the ages of six months and three years, from low socio-economic status.  Martha Farah, director of the University of Pennsylvania’s centre for cognitive neuroscience, said: ‘The biggest effects are on language and memory. The finding about memory impairment – the ability to encounter a pattern and remember it – really surprised us’.” 
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Pattern #2

The current issue of Harvard Magazine has a cover article on autism.  In reading through the piece, I was struck by this one line about Asperger’s syndrome: “they shared key impairments in social interaction, reciprocal communication, and imagination (i.e., repetitive behaviors and interests).”  It many ways this description struck me as presenting a similar dichotomy to addiction, where the repetitive behaviors and interests are linked diagnostically with failed social roles, family difficulties and “denial” in communication. 

I am not saying that addiction and autism are the same, or that biologically or phenomenology they come from similar causes or problems.  But I do wonder if the rush to focus in on singular brain circuits leads us to overlook the human dimensions of imagination, sociality, and behavior.  These abilities and practices are linked in profound ways in everyday life, and thus will drive biology in profound ways. 

Sandy G, who linked to us (thanks!) through his post on The Rat Park, has several posts on autism.  In one on joint attention, he relates Tomasello’s recent work: “The authors concluded that, at least at this developmental period, children with autism seem to understand the social components of situations that call for “helping” behaviors and engage in helping behaviors, but only when such help does not require interpersonal cooperation. However, when cooperation is required to complete the task, these children are less likely to correctly engage with another partner, possibly because the unique “shared” component of cooperation. That is, cooperation requires shared goals, shared attention, and a shared plan of action, processes that seem to be affected in children with autism.” 
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Addiction and Our Faultlines

Blogging on Peer-Reviewed ResearchDrugs are what cause drug addiction, or so is the story we often hear in the United States.  But what if social conditions mattered as much or more in who used and abused drugs?

 Many anthropologists and other social scientists have shown that social conditions matter, including Phillippe Bourgois, Merrill Singer, and Elliott Currie.  Bourgois’ book In Search of Respect, Singer’s article Why Does Juan Garcia Have A Drinking Problem, and Currie’s Reckoning are powerful testaments to a basic point: Addiction runs along the fault lines of society.

 However, it has been relatively easy for neuroscientists to isolate themselves from that view, and to argue that drugs run along the pharmacological fault lines of the brain, generating terrible problems on their own.  Social conditions are one thing, drugs and brains are another.

 The research by Michael Nader, Morgan Drake and colleagues shows convincingly that social conditions matter, and matter a great deal, at the basic level of the brain.  This same line of research also highlights that individual differences, whether genetic or social, make a difference in addiction.  The trick is that the research is done with monkeys.

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Thinking about how others think: two ways?

Blogging on Peer-Reviewed ResearchJason Mitchell and Mahzarin R. Banaji, of Harvard University, and C. Neil Macrae, at the University of Aberdeen, published a fascinating piece in Neuron in May 2006, ‘Dissociable Medial Prefrontal Contributions to Judgments of Similar and Dissimilar Others’ (abstract on PubMed or pdf download here). I came across the article through the Mind Matters blog in a piece by Stephen Macknik (director of the Laboratory of Behavioral Neurophysiology at the Barrow Neurological Institute in Phoenix), entitled How Harvard students perceive rednecks: The neural basis for prejudice. Both the original article and the blog post by Macknik are worth checking out.

In the experiment, the team headed by Mitchell showed the subjects photographs and asked the subjects questions about the beliefs, feelings, or attitudes of the people in the pictures. Subjects were told the pictures were of either ‘liberal northeastern’ or ‘conservative Midwest fundamentalist Christian students’ after doing a survey which determined which group the subjects were most like. The categories for the photographs were false, the pictures being taken from dating websites and randomly assigned to either of the groups. The photos were reassigned for each subject, and gender, age and other distinguishing marks controlled for (or likely just avoided by the original choice of photos). In other words, college students were being told that other ‘college students’ were either ‘like them’ or ‘different from them,’ with (apparently) no visual cues for either identity. The research team was interested in what parts of the brain were being used in attempts to ‘mentalize,’ that is, to perceive the thoughts, motives or perceptions of others.

In particular, the researchers discussed that slightly different parts of the medial prefrontal cortex (mPFC) are used when trying to mentalize, depending upon whether the target of observation is believed to be similar or dissimilar (should I write ‘the Other’ to prove I’m a cultural anthropologist?) to the self. Specifically, a more ventral (front) part of mPFC is used when ‘mentalizing’ about others perceived as similar, as opposed to a higher (dorsal) part of the mPFC used to deduce the thinking or feelings of others when confronted with photos of people thought to be ‘unlike’ themselves. The difference is significant because the different regions suggest that these perceptions are being accomplished in distinct fashion.

… simulation theories of social cognition suggest that this [ventral] region should be specifically engaged for mental state inferences about others perceived to be similar to oneself, since mentalizing on the basis of self knowledge can only take place if another person’s internal experience is assumed to be comparable to one’s own. As such, this hypothesis suggests an important ‘‘division of labor’’ in the contributions made by different subregions of mPFC to mentalizing. Whereas ventral mPFC may be expected to contribute to mental state inferences about similar others, the dorsal [upper or top] aspects of mPFC—more traditionally associated with mentalizing tasks—should be specifically engaged by mentalizing about dissimilar others, that is, individuals for whom overlap between self and other cannot be assumed.

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The Family Dinner Deconstructed

National Public Radio had a radio broadcast yesterday morning on “The Family Dinner Deconstructed.”  Here’s the blurb: “The ritual of a family dinner has been praised as an antidote to bad grades and bad habits in kids. But as researchers look closer at the family dinner, they raise the question: Is it the mere act of eating together that counts, or is it that strong families are already more likely to have a family dinner?” 

The reporter does a wonderful job talking with a variety of researcher to focus in on the proximate features of the family dinner—conversations, relationships, rituals, emotions—and how they can impact physical and mental health.  For example, the quality of conversations at mealtime was a better predictor of reading development than parents actually reading to their children.  But what mattered was the content on dinner conservation, that it was complex and “rich with explanation, story telling, and more.”  Similarly, for physical and mental development (for example, eating disorders), specific behaviors at dinner proved important: roles assigned (setting the table, beginning and end to dinner); a genuine concern about daily activities; and a sense of empathy and concern for each other. 

While the radio cast pushes a double-blind study to “determine” the specific effects of a good-quality family dinner versus dinner-as-usual, the announcer rightly acknowledges that doing such research is a daunting prospect.  I would add that an ethnographic approach that builds on this educational and psychological research and that teases out the relationships between dinner, family interaction, and development as a joint physical-mental phenomenon could also add some great insights.