Monday, July 30, 2012

Beyond the blink - the art of delay

I pass on two interesting and related pieces on the limits of rapid spontaneous intuition judgements and actions, contra Malcolm Gladwell. Partnoy describes the spectacle of the initial reporting rush that incorrectly described the recent Supreme Court decision on health care, a case of focused "present bias" that would have been avoided by waiting and reading a bit further into the court decision. Brain pickings points to Partnoy's more scholarly and extended treatment of this issue in its piece on his new book.
Thinking about the role of delay is a profound and fundamental part of being human. Questions about delay are existential: the amount of time we take to reflect on decisions will define who we are. Is our mission simply to be another animal, responding to whatever stimulations we encounter? Or are we here for something more? ...Our ability to think about delay is a central part of the human condition. It is a gift, a tool we can use to examine our lives. Life might be a race against time, but it is enriched when we rise above our instincts and stop the clock to process and understand what we are doing and why. A wise decision requires reflection, and reflection requires pause. The converse of Socrates’s famous admonition is that the examined life just might be worth living.

Friday, July 27, 2012

Aphorisms and the Commodification of Wisdom

I pass on this nice bit from Brain Pickings on some Susan Sontag writing. One chunk:
Aphorisms are rogue ideas.
Aphorism is aristocratic thinking: this is all the aristocrat is willing to tell you; he thinks you should get it fast, without spelling out all the details. Aphoristic thinking constructs thinking as an obstacle race: the reader is expected to get it fast, and move on. An aphorism is not an argument; it is too well-bred for that.
To write aphorisms is to assume a mask — a mask of scorn, of superiority. Which, in one great tradition, conceals (shapes) the aphorist’s secret pursuit of spiritual salvation. The paradoxes of salvation. We know at the end, when the aphorist’s amoral, light point-of-view self-destructs.

Wednesday, July 25, 2012

Compassion towards one person generalizes to others.

DeSteno does a NYTimes OpEd piece to point to his papers in the Journal of Experimental Social Psychyology (PDF here) and the journal Emotion (PDF here). Clips:
Whether it’s the parable of the good Samaritan in Christianity, Judaism’s “13 attributes of compassion” or the Buddha’s statement that “loving kindness and compassion is all of our practice,” empathy with the suffering of others is seen as a special virtue that has the power to change the world. This idea is often articulated by the Dalai Lama, who argues that individual experiences of compassion radiate outward and increase harmony for all.
...does the experience of compassion toward one person measurably affect our actions and attitudes toward other people? If so, are there practical steps we can take to further cultivate this feeling? Recently, my colleagues and I conducted experiments that answered yes to both questions.
The links provided give the details of the experiments, here are the abstracts, first on the generalization of compassion:
The ability of compassion felt toward one person to reduce punishment directed at another was examined. The use of a staged interaction in which one individual cheats to earn higher compensation than others resulted in heightened third-party punishment being directed at the cheater. However, among participants who were induced to feel compassion toward a separate individual, punishment of the cheater disappeared even though the cheater clearly intended to cheat and showed no remorse for doing so. Moreover, additional analyses revealed that the reduction in punishment was directly mediated by the amount of compassion participants experienced toward the separate individual.
And second, on a technique to foster compassion:
Although evidence has suggested that synchronized movement can foster cooperation, the ability of synchrony to increase costly altruism and to operate as a function of emotional mechanisms remains unexplored. We predicted that synchrony, due to an ability to elicit low-level appraisals of similarity, would enhance a basic compassionate response toward victims of moral transgressions and thereby increase subsequent costly helping behavior on their behalf. Using a manipulation of rhythmic synchrony, we show that synchronous others are not only perceived to be more similar to oneself but also evoke more compassion and altruistic behavior than asynchronous others experiencing the same plight. These findings both support the view that a primary function of synchrony is to mark others as similar to the self and provide the first empirical demonstration that synchrony-induced affiliation modulates emotional responding and altruism.

Monday, July 23, 2012

Half a heartbeat can chill out our response to threat.

Whether we are breathing in or breathing out can have a pronounced effect on our threat detection threshold. Meditation regimes and stress performance training (as for Navy Seals) emphasize prolongation of exhalation as a calming technique. During exhalation, measurements have shown a relative increase in parasympathetic and vagal activity, a relative decrease in amygdala reactivity, and lower reactivity to possible threats. Now work of Garfinkel and colleagues, reported at the recent meeting on the Assoc. for the Scientific Study of Consciousness in Brighton, U.K. (meeting abstracts here, 4.7 MB download) shows that the cardiac cycle can influence our emotional response to scary stimuli. Here is a clip from the writeup in The New Scientist:
In one experiment...people were asked to look at a stream of flashing images and highlight when they spotted a face. Some of the faces looked fearful, others looked neutral...Unbeknown to the volunteers, images were time-locked to appear in sync with their heart-beat. Sometimes the images were synced with the systole phase - the part of the cardiac cycle where the heart muscle contracts to squeeze blood out of the heart, at other times they were linked to the diastole phase - the stage where the heart relaxes and fills after contracting...people were better at spotting fearful faces compared with neutral faces, but only when the pictures were timed to appear at the systole phase.
In another study, people saw the same pictures while having their brain scanned using MRI. People had a stronger response in the hippocampus and amygdala - areas of the brain associated with fear - when they were shown fearful faces at systole than when they saw them at diastole. In other words, half a heartbeat was all it took for a person to experience a significantly different response to the same scary stimulus...The finding seems to be mediated by barorecepors - stretch and pressure sensitive receptors in the heart and surrounding arteries which help initiate systole. "When barroreceptors are activated at systole, a flurry of activity is transferred to the brain at that moment," Garfinkel says, which could explain the difference in the brain scans.
It is not at all clear whether this is a functional adaptation, but other studies show heartbeat can mediate other emotional functions, such as empathy and overt fear responses.

Thursday, July 19, 2012

Why are conservatives happier?

The New York Times has had a nice chunk of commentary on explanations for why many studies show people of conservative political persuasion report themselves to be happier than liberals. The article by Arthur Brooks who (red flag for Deric) is president of the American Enterprise Institute notes several common explanations based on lifestyle (marriage, faith)
Fifty-two percent of married, religious, politically conservative people (with kids) are very happy — versus only 14 percent of single, secular, liberal people without kids.
Some further clips from Brooks:
An explanation for the happiness gap more congenial to liberals is that conservatives are simply inattentive to the misery of others...conservatives do indeed see the free enterprise system in a sunnier light than liberals do, believing in each American’s ability to get ahead on the basis of achievement. Liberals are more likely to see people as victims of circumstance and oppression, and doubt whether individuals can climb without governmental help. other noteworthy political happiness gap that has gotten less scholarly attention than conservatives versus liberals: moderates versus extremists...People at the extremes are happier than political moderates. Correcting for income, education, age, race, family situation and religion, the happiest Americans are those who say they are either “extremely conservative” (48 percent very happy) or “extremely liberal” (35 percent). Everyone else is less happy, with the nadir at dead-center “moderate” (26 percent)...What explains this odd pattern? One possibility is that extremists have the whole world figured out, and sorted into good guys and bad guys. They have the security of knowing what’s wrong, and whom to fight. They are the happy warriors.
A followup in a "Letters to the Editor" piece contains a number of comments:
"Much research implies that happiness depends on brain chemistry (the pharmaceutical industry thinks so) and might, to some extent, be hard-wired. So maybe happiness makes us conservative, not vice versa...It’s logical that happy Americans would be suspicious of change: that they’d be conservative. And that unhappy Americans, wanting to feel happier, would prefer change: that they’d be liberal...Or maybe some unhappy Americans are unhappy because America is relatively conservative: that conservatism by some breeds unhappiness in others. The happiest countries (according to the World Happiness Report, Denmark, Norway, Finland and the Netherlands) are more liberal than America...Presumably, many people manage to be both happy and liberal, at least by our standards."
"I agree with Arthur C. Brooks that conservatives may be happier than liberals. A parallel may be found in the French society of the 18th century...Versailles and its gardens may testify to the splendor of life for the French aristocrats; similarly, the palaces in St. Petersburg may testify to the sense of well-being among the Russian nobility. This contentment could not have existed without some of the clergy encouraging the aristocrats to enjoy their status and not be concerned with the misery of the lower classes...We know how huge upheavals put an end to this obliviousness, but history is replete with lessons not learned."
"Arthur C. Brooks argues that conservatives are happier than liberals in part because of their emphasis on faith... But the emphasis on faith-based “knowledge” among some conservatives has led to an unwillingness to accept reality. Some deny evolution, or that global warming exists, or that bank misbehavior was a major cause of the Great Recession, and so on...The denial or ignorance of these depressing facts might well explain some of the conservative bliss."
"... “Don’t Indulge. Be Happy,” by Elizabeth Dunn and Michael Norton (Sunday Review, July 8), tells us that once you have reached $75,000 a year, earning more doesn’t really make you happier...It may be that “conservatives are happier than liberals” because they are more likely to have reached that $75,000 income level."

Tuesday, July 17, 2012

MindBlog summer vacation schedule

I've decided to chill for a bit, relax from the daily postings, take a summer break. (Maybe this is influenced by the amazing heat wave and drought we are experiencing in the midwest. It saps energy and motivation.) So, if the spirit moves me to putter with a posting, I'll do it. If not, that's also OK...

Monday, July 16, 2012

Monday music offering. Faure Barcarolle No. 4

Here is the second of the two Faure Baracolles I did at a May 27 recital and recorded on July 5.

Friday, July 13, 2012

Religion replenishes self-control.

In four experiments Rounding et al. activate god-related concepts in participants without their conscious awareness, using an implicit-priming procedure that required participants to unscramble each of 10 five-word sentences by dropping an irrelevant word. Half of the sentences contained neutral words only ,and the remaining sentences contained one religious-prime word. A procedure like this evokes very little conscious awareness of the primed material, and participants who were suspicious of the primed material or who guessed the hypotheses of the study were excluded from the analyses. Next, participants engaged tasks that tested enduring discomfort, delayed gratification, or persistence with or without ego depletion. A forth condition used primes that were not religious, but suggested morality (such as righteous, virtue, or moral) or death (such as extinct, grave, or deadly). The researcher found religious priming most effective in increasing, or regenerating, self control. Here is their abstract:
Researchers have proposed that the emergence of religion was a cultural adaptation necessary for promoting self-control. Self-control, in turn, may serve as a psychological pillar supporting a myriad of adaptive psychological and behavioral tendencies. If this proposal is true, then subtle reminders of religious concepts should result in higher levels of self-control. In a series of four experiments, we consistently found that when religious themes were made implicitly salient, people exercised greater self-control, which, in turn, augmented their ability to make decisions in a number of behavioral domains that are theoretically relevant to both major religions and humans’ evolutionary success. Furthermore, when self-control resources were minimized, making it difficult for people to exercise restraint on future unrelated self-control tasks, we found that implicit reminders of religious concepts refueled people’s ability to exercise self-control. Moreover, compared with morality- or death-related concepts, religion had a unique influence on self-control.

Thursday, July 12, 2012

Scary?..Google X making a digital human brain?

I have a major love/hate affair with google. This MindBlog uses google's blogger service, and so utterly depends on it, all my email addresses forward to my gmail account, I use it to synchronize all my calendar, documents, spreadsheets, and contacts, across multiple devices. I use google voice for phoning, google+ hangouts for video chats, etc. etc. Google's services have become such a prosthesis for me that I am quite helpless away from its Cloud. At the same time, I resist as many of the 'connectivity' efforts as much as I can. I emphatically do not want to know whether a friend is nearby, and don't want people following me. I think we are constantly flirting with the 'uncanny valley' effect, where what might be useful suddenly becomes very spooky.

In this vein, a recent article noting google's efforts to model the human brain made me both excited, interested, and terrified at the same time. Google's brain used an array of 16,000 processors to create a neural network with more than one billion connections, and presented it with 10 million digital images found in YouTube videos. Without any instructions or labels, it learned to detect faces, human bodies, and cats! This suggests that the human brain, which has at least a million times more connections than this model, could learn significant classes of stimuli with minimum genetic nudging other than instructions for making nerves cells whose connections can be shaped by the sensory input received. 

Here is the abstract from Le et al.(PDF here):
We consider the problem of building high-level, class-specific feature detectors from only unlabeled data. For example, s it possible to learn a face detector using only unlabeled images? To answer this, we train a 9- layered locally connected sparse autoencoder with pooling and local contrast normalization on a large dataset of images (the model has 1 billion connections, the dataset has 10 million 200x200 pixel images downloaded from the Internet). We train this network using model parallelism and asynchronous SGD on a cluster with 1,000 machines (16,000 cores) for three days. Contrary to what appears to be a widely-held intuition, our experimental results reveal that it is possible to train a face detector without having to label images as containing a face or not. Control experiments show that this feature detector is robust not only to translation but also to scaling and out-of-plane rotation. We also found that the same network is sensitive to other high-level concepts such as cat faces and human bodies. Starting with these learned features, we trained our network to obtain 15.8% accuracy in recognizing 20,000 object categories from ImageNet, a leap of 70% relative improvement over the previous state-of-the-art.

Wednesday, July 11, 2012

Thinking in a foreign language reduces decision biases.

From Keyser et al.:
Would you make the same decisions in a foreign language as you would in your native tongue? It may be intuitive that people would make the same choices regardless of the language they are using, or that the difficulty of using a foreign language would make decisions less systematic. We discovered, however, that the opposite is true: Using a foreign language reduces decision-making biases. Four experiments show that the framing effect disappears when choices are presented in a foreign tongue. Whereas people were risk averse for gains and risk seeking for losses when choices were presented in their native tongue, they were not influenced by this framing manipulation in a foreign language. Two additional experiments show that using a foreign language reduces loss aversion, increasing the acceptance of both hypothetical and real bets with positive expected value. We propose that these effects arise because a foreign language provides greater cognitive and emotional distance than a native tongue does.

Tuesday, July 10, 2012

'Crazy busy' and internet distractions...

I wanted to pass on two recent NYTimes pieces: Tim Kreider makes the point that the 'busy' trap that many people drive themselves into the ground with is entirely a matter of their own choice:
Busyness serves as a kind of existential reassurance, a hedge against emptiness; obviously your life cannot possibly be silly or trivial or meaningless if you are so busy, completely booked, in demand every hour of the day...More and more people in this country no longer make or do anything tangible; if your job wasn’t performed by a cat or a boa constrictor in a Richard Scarry book I’m not sure I believe it’s necessary. I can’t help but wonder whether all this histrionic exhaustion isn’t a way of covering up the fact that most of what we do doesn’t matter.
Idleness is not just a vacation, an indulgence or a vice; it is as indispensable to the brain as vitamin D is to the body, and deprived of it we suffer a mental affliction as disfiguring as rickets. The space and quiet that idleness provides is a necessary condition for standing back from life and seeing it whole, for making unexpected connections and waiting for the wild summer lightning strikes of inspiration — it is, paradoxically, necessary to getting any work done...Archimedes’ “Eureka” in the bath, Newton’s apple, Jekyll & Hyde and the benzene ring: history is full of stories of inspirations that come in idle moments and dreams. It almost makes you wonder whether loafers, goldbricks and no-accounts aren’t responsible for more of the world’s great ideas, inventions and masterpieces than the hardworking.
Jenna Wortham notes her experience that taking breaks to aimlessly wander around the Web during focused assignments seemed to make her more efficient. She then notes research asking whether the plasticity of our brains might be allow us to adapt to multi-tasking:
...consensus among scientists and researchers is that trying to juggle many tasks fractures our thinking and degrades the quality of each action. But understanding the plasticity of the brain, or its ability to adapt and reorganize its pathways, is still in its early stages...It may be that the brain — or some brains — can handle certain levels of multitasking and not others, he said. Surfing the Web and talking on the phone may not place the same demand on available cognitive resources as, say, cruising down the highway and sending a text message. It’s an area of research that scientists and psychologists are just starting to explore...if abilities can actually improve, the question is, by how much?

Monday, July 09, 2012

A Faure Barcarolle

I pass on this recording I made a few days ago of the Faure Barcarolle (Gondolier's song) No. 2. It is a piece I did at a May 27 musical at my home that I have mentioned earlier.

Friday, July 06, 2012

Metarepresentations explain human uniqueness.

I pass along this essay by Hugo Mercier:
Humans alone fluently understand the mental states of others. Humans alone rely on an open-ended system of communication. Humans alone ponder the reasons for their beliefs. For each of these feats, and for others too, humans rely on their most special gift: the ability to represent representations—the ability to form metarepresentations. Hidden behind such mundane thoughts as "Mary believes that Paul believes that it's going to rain" is the explanation of human uniqueness.

There are two ways to represent representations: one immensely powerful, the other rather clumsy. The clumsy way is to create a new representation for every representation that needs to be represented. Using such a device, Mary would have to form a representation "Paul believes that it's going to rain" completely independent of her representation "it's going to rain." She would then have to learn anew all of the inferences that can be drawn from "Paul believe it's going to rain," such as the negative impact on the willingness to go for a jog or the increased probability to fetch an umbrella. This cumbersome process would have to be repeated for each new representation that Mary wishes to attribute, from "Peter things the weather looks lovely" to "Ruth is afraid that the Dow Jones is going to crash tomorrow." Such a process could not possibly account for humans' amazing abilities to attribute just about any thought to other people. How can we account for these skills then?

The explanation is that we use our own representations to attribute thoughts to others. When Mary wants to attribute to Paul the belief "it's going to rain," she 'simply' uses her representation "it's going to rain" and embeds it in a metarepresentation: "Paul thinks "it's going to rain."" Because the same representation is used, Mary can take advantage of the inferences that she could draw from "it's going to rain" to draw inferences from "Paul believes that "it's going to rain."" This trick opened for humans the doors to an unparalleled understanding of their social environment.

Most of the beliefs we form about others are derived from communication: people keep telling us what they believe, want, desire, fear, love… Here again, metarepresentations play a crucial role, since understanding language requires going from utterances—"It's going to rain"—to metarepresentations—"Paul means that "it will soon rain here.""

Mentalizing (attributing thoughts to others) and communicating are the most well known uses of metarepresentations, but they are not the only ones. Metarepresentations are also essential for people to be able to think about reasons. Specific metarepresentations are relied on when people produce and evaluate arguments, as in: "Mary thinks "it's going to rain" is a good argument for "we should not go out."" Again, Mary uses her representation "it's going to rain" but, instead of attributing it to someone else, she represents its strength as a reason to accept a given conclusion.

Several other properties of representations can be represented, from their esthetic value to their normative status. The representational richness made possible by recycling our own representations to represent other people's representations, or to represent other attributes of representations, is our most distinctive trait, one of these amazingly brilliant solutions that natural selection stumbles upon. However, if it is indeed much simpler to rely on this type of metarepresentations than on the cumbersome solution of creating new representations from scratch every time, we still face a complex computational task.

Using the example of mentalizing, it is apparent that even when we use our own representations to attribute representations to other people, a lot of work remains to be done. It cannot be metarepresentations all the way down: at some point, other inputs—linguistic or behavioral cues—have to be used to attribute representations. Moreover, when a representation is represented not all of the inferences that can be drawn from it are relevant. When Mary believes that John believes it's going to rain, some of the inferences that she would draw from "it's going to rain" may not be attributable to John—maybe he doesn't mind jogging in the rain for instance. Other inferences Mary may not spontaneously draw—maybe John will be worried because he has left his book outside. Still, without a baseline—Mary's own representation—the task would jump from merely difficult to utterly intractable.

Probably more than any other cognitive trait, the ability to use our own representations to represent representations is what explains humans' achievements. Without this skill, the complex forms of social cognition that characterize our species would have been all but impossible. It is also critical for us psychologists to understand these ideas if we want to continue our forays into human cognition.

I leave the last word to Dan Sperber who, more than any other cognitive scientists, has made of metarepresentations the most central explanation of humans' unique cognition: "Humans have the ability to represent representations. I would argue that this meta-representational ability is as distinctive of humans, and as important in understanding their behaviour, as is echolocation for bats."

Thursday, July 05, 2012

Mechanisms of white matter changes induced by meditation.

Diffusion tensor imaging (DTI) is a noninvasive MRI-based technique that can delineate white matter fibers in vivo, measure white matter’s structural plasticity to demonstrate that training or learning alters brain white matter. Fractional anisotropy (FA) is an important index for measuring the integrity of white matter fibers. In general, a higher FA value has been related to improved performance, and reduced FA has been found in normal aging and in neurological or psychiatric disorders. Posner and collaborators now show more details about changes that occur with only 4 weeks of meditation training (One suspects these changes might reverse after cessation of meditation practice?):
Using diffusion tensor imaging, several recent studies have shown that training results in changes in white matter efficiency as measured by fractional anisotropy (FA). In our work, we found that a form of mindfulness meditation, integrative body–mind training (IBMT), improved FA in areas surrounding the anterior cingulate cortex after 4-wk training more than controls given relaxation training. Reductions in radial diffusivity (RD) have been interpreted as improved myelin but reductions in axial diffusivity (AD) involve other mechanisms, such as axonal density. We now report that after 4-wk training with IBMT, both RD and AD decrease accompanied by increased FA, indicating improved efficiency of white matter involves increased myelin as well as other axonal changes. However, 2-wk IBMT reduced AD, but not RD or FA, and improved moods. Our results demonstrate the time-course of white matter neuroplasticity in short-term meditation. This dynamic pattern of white matter change involving the anterior cingulate cortex, a part of the brain network related to self-regulation, could provide a means for intervention to improve or prevent mental disorders.
Here is their description of the integrative body-mind training (IBMT) used:
IBMT involves body relaxation, mental imagery, and mindfulness training, accompanied by selected music background. Cooperation between the body and the mind is emphasized in facilitating and achieving a meditative state. The trainees concentrated on achieving a balanced state of body and mind guided by an IBMT coach and the compact disk. The method stresses no effort to control thoughts, but instead a state of restful alertness that allows a high degree of awareness of body, mind, and external instructions (5, 16, 19). RT involves the relaxing of different muscle groups over the face, head, shoulders, arms, legs, chest, back, and abdomen, guided by a tutor and compact disk. With eyes closed and in a sequential pattern, one is forced to concentrate on the sensation of relaxation, such as the feelings of warmth and heaviness. This progressive training helps the participant achieve physical and mental relaxation and calmness.

Wednesday, July 04, 2012

Hierarchy increases group effectiveness.

From Ronay et al.:
Two experiments examined the psychological and biological antecedents of hierarchical differentiation and the resulting consequences for productivity and conflict within small groups. In Experiment 1, which used a priming manipulation, hierarchically differentiated groups (i.e., groups comprising 1 high-power-primed, 1 low-power-primed, and 1 baseline individual) performed better on a procedurally interdependent task than did groups comprising exclusively either all high-power-primed or all low-power-primed individuals. There were no effects of hierarchical differentiation on performance on a procedurally independent task. Experiment 2 used a biological marker of dominance motivation (prenatal testosterone exposure as measured by a digit-length ratio) to manipulate hierarchical differentiation. The pattern of results from Experiment 1 was replicated; mixed-testosterone groups achieved greater productivity than did groups comprising all high-testosterone or all low-testosterone individuals. Furthermore, intragroup conflict mediated the productivity decrements for the high-testosterone but not the low-testosterone groups. This research suggests possible directions for future research and the need to further delineate the conditions and types of hierarchy under which hierarchical differentiation enhances rather than undermines group effectiveness.

Tuesday, July 03, 2012

Connectivity of prefrontal cortex predicts cognitive control and intelligence

From Cole et al.:
Control of thought and behavior is fundamental to human intelligence. Evidence suggests a frontoparietal brain network implements such cognitive control across diverse contexts. We identify a mechanism—global connectivity—by which components of this network might coordinate control of other networks. A lateral prefrontal cortex (LPFC) region's activity was found to predict performance in a high control demand working memory task and also to exhibit high global connectivity. Critically, global connectivity in this LPFC region, involving connections both within and outside the frontoparietal network, showed a highly selective relationship with individual differences in fluid intelligence. These findings suggest LPFC is a global hub with a brainwide influence that facilitates the ability to implement control processes central to human intelligence.
Figure - Cognitive control regions, as defined by successful cognitive control. A, Regions of Interest (ROIs) were defined based on brain activity during successful N-back task performance. The following highly selective criteria were used: preferential activation for trials requiring flexible control (lures), correct > incorrect trials, positive correlation with accuracy across participants. All 3 of these regions were hubs (in top 10% connectivity in the brain).

Monday, July 02, 2012

Hygiene can hurt.

I pass on this summary from the Editor's choice section of Science, follwed by the abstract of the work mentioned. It describes further work on how failure to interact with natural environments during childhood can lead to later chronic inflammatory disorders. Also, relevant to this topic is a recent Op-Ed piece in the NYTimes called "Dirtying Up Our Diets.", and this further piece discusses our human microbiome.
As human societies urbanize, chronic inflammatory disorders become more apparent. The hygiene hypothesis suggests that individuals exposed to infection in childhood are less likely to develop inflammatory disease because exposure to microorganisms is important for stimulating responses that maintain epithelial cell integrity. Hence, in urban environments, reduced contact with the full diversity of the microbial world may be leading to the increased incidence of inflammatory disorders. Hanski et al. took a random sample of 118 adolescents from towns, villages, and isolated dwellings in eastern Finland, tested their immune function and allergic responses, surveyed their skin microflora, and investigated the biodiversity within their homes. They found several significant correlations, not least that low biodiversity was surprisingly strongly associated with atopy, and concluded that humans need to interact with natural environments for their physical health, not just for their peace of mind.
Here is the Hanski et al. abstract:
Rapidly declining biodiversity may be a contributing factor to another global megatrend—the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations worldwide. According to the “biodiversity hypothesis,” reduced contact of people with natural environmental features and biodiversity may adversely affect the human commensal microbiota and its immunomodulatory capacity. Analyzing atopic sensitization (i.e., allergic disposition) in a random sample of adolescents living in a heterogeneous region of 100 × 150 km, we show that environmental biodiversity in the surroundings of the study subjects’ homes influenced the composition of the bacterial classes on their skin. Compared with healthy individuals, atopic individuals had lower environmental biodiversity in the surroundings of their homes and significantly lower generic diversity of gammaproteobacteria on their skin. The functional role of the Gram-negative gammaproteobacteria is supported by in vitro measurements of expression of IL-10, a key anti-inflammatory cytokine in immunologic tolerance, in peripheral blood mononuclear cells. In healthy, but not in atopic, individuals, IL-10 expression was positively correlated with the abundance of the gammaproteobacterial genus Acinetobacter on the skin. These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general.