The Neurochemistry of Storytelling.

Having in the previous post just made an ill-tempered dump on one kind of popularization, I decide to be inconsistent and now pass on this nice piece with a little less pizazz from the Brain Pickings Newsletter, on how storytelling can engage our brain neurochemistry associated with stress and empathy. It is a very effective and touching piece, and I recommend that you watch the video below:

Brain Showbiz...

Put me down as a curmudgeonly old fart, but I'm not getting a 'gee whiz' response to a recent promotional email asking for publicity on a rhythm and the brain project. It's cute, the graphics are kewl, but the science is out to lunch - it seems to me more like publicity seeking and self promotion masquerading as brain science.

Conscious awareness not required for our placebo or nocebo responses.

Interesting observations from Jensen et al. They first condition a placebo (beneficial) or nocebo (adverse) reponse to a thermal pain stimulus, and then find subliminal (non-conscious) presentation of the conditioning cues elicits the same responses. Their abstract:

The dominant theories of human placebo effects rely on a notion that consciously perceptible cues, such as verbal information or distinct stimuli in classical conditioning, provide signals that activate placebo effects. However, growing evidence suggest that behavior can be triggered by stimuli presented outside of conscious awareness. Here, we performed two experiments in which the responses to thermal pain stimuli were assessed. The first experiment assessed whether a conditioning paradigm, using clearly visible cues for high and low pain, could induce placebo and nocebo responses. The second experiment, in a separate group of subjects, assessed whether conditioned placebo and nocebo responses could be triggered in response to nonconscious (masked) exposures to the same cues. A total of 40 healthy volunteers (24 female, mean age 23 y) were investigated in a laboratory setting. Participants rated each pain stimulus on a numeric response scale, ranging from 0 = no pain to 100 = worst imaginable pain. Significant placebo and nocebo effects were found in both experiment 1 (using clearly visible stimuli) and experiment 2 (using nonconscious stimuli), indicating that the mechanisms responsible for placebo and nocebo effects can operate without conscious awareness of the triggering cues. This is a unique experimental verification of the influence of nonconscious conditioned stimuli on placebo/nocebo effects and the results challenge the exclusive role of awareness and conscious cognitions in placebo responses.

Clever crows! Now shown to reason about hidden causes.

Behavioral studies on New Caledonian crows, especially over the past twenty years, continue to yield amazing results. (A video I first posted for my Biology of Mind course over ten years ago showing some of this earlier work has received 125,000 viewings!). Taylor et al. now demonstrate reasoning about hidden causes:

The ability to make inferences about hidden causal mechanisms underpins scientific and religious thought. It also facilitates the understanding of social interactions and the production of sophisticated tool-using behaviors. However, although animals can reason about the outcomes of accidental interventions, only humans have been shown to make inferences about hidden causal mechanisms. Here, we show that tool-making New Caledonian crows react differently to an observable event when it is caused by a hidden causal agent. Eight crows watched two series of events in which a stick moved. In the first set of events, the crows observed a human enter a hide, a stick move, and the human then leave the hide. In the second, the stick moved without a human entering or exiting the hide. The crows inspected the hide and abandoned probing with a tool for food more often after the second, unexplained series of events. This difference shows that the crows can reason about a hidden causal agent. Comparative studies with the methodology outlined here could aid in elucidating the selective pressures that led to the evolution of this cognitive ability.

Kids as little scientists - early academics can be misguided

A review article by Gopnik offers an interesting perspective:

New theoretical ideas and empirical research show that very young children’s learning and thinking are strikingly similar to much learning and thinking in science. Preschoolers test hypotheses against data and make causal inferences; they learn from statistics and informal experimentation, and from watching and listening to others. The mathematical framework of probabilistic models and Bayesian inference can describe this learning in precise ways. These discoveries have implications for early childhood education and policy. In particular, they suggest both that early childhood experience is extremely important and that the trend toward more structured and academic early childhood programs is misguided.

Opps! Sex does decrease human male lifespan.

Animal studies have suggested that castration increases lifespan in males, and now Korean researchers have examined genealogy records and lifespan of 81 Korean eunuchs to find that their average lifespan is ~14-19 years longer than that of non-castrated men of similar class. (I doubt this finding will lead to an uptick in voluntary male castrations, the trade off of minus fifteen years for what our male sex hormones make possible doesn’t seem so bad...) The abstract:

Although many studies have shown that there are trade-offs between longevity and reproduction, whether such trade-offs exist in humans has been a matter of debate. In many species, including humans, males live shorter than females, which could be due to the action of male sex hormones. Castration, which removes the source of male sex hormones, prolongs male lifespan in many animals, but this issue has been debated in humans. To examine the effects of castration on longevity, we analyzed the lifespan of historical Korean eunuchs. Korean eunuchs preserved their lineage by adopting castrated boys. We studied the genealogy records of Korean eunuchs and determined the lifespan of 81 eunuchs. The average lifespan of eunuchs was 70.0 ± 1.76 years, which was 14.4–19.1 years longer than the lifespan of non-castrated men of similar socio-economic status. Our study supports the idea that male sex hormones decrease the lifespan of men.

Followup on evolutionary psychology as ' just so stories'

A comment on my Sept. 28 post has passed on a number of excellent response to the book review I was noting in that post. I was remiss (lazy) in not taking to task one absurd contention of the reviewer, namely that "you don’t have to know about the evolution of an organ in order to understand it." (a third of my Biology of Mind Book argued the contrary.) After Jabr notes in his Scientific American comments several examples of how understanding the evolution of different brain areas has enhanced understanding and medical practice, he gives this nice analogy:

Studying the brain and mind in ignorance of its vast evolutionary tale does not make sense. It would be equivalent to an archaeologist discovering the remains of an enormous tapestry, slicing out a particular figure from the cloth and claiming that he could learn everything he needs to know by examining that figure in isolation. Even if the archaeologist described the figure in exquisite detail, taking it apart thread by thread and sewing it back together, he would remain willfully oblivious of the whole story. In the same way, disregarding the human brain’s history limits psychology and neuroscience to a paltry understanding of our brains and minds.

The comment also points to Kurzban and Gottschall as offering further commentary.

Also, let me note this comment on the Sept 28 post by Jim Birch:

I'm a little surprised by the animosity directed at evolutionary psychology. For me, it has provided revolutionary insights and understanding. In particular, the general notion that in biology, energy is not wasted, it is utilized adaptively. Under evolution, "adaptive" is not local in time and space but statistically selected over a period and range of the species' evolution.

This gives, or actually requires, a new way of interpreting any human behaviour: as statistically adaptive. And in doing so, it blasts away the incoherent mass of narrative explanations that have been conventionally applied. Our "craziest" tendencies like dying on Everest or blowing life savings on poker machines are no longer down to Freudian death wishes or moral failings (etc) but can be seen as adaptive behaviours operating badly, or even just out of context.

Of course, no one was around in the Pleistocene recording behaviours and survival rates so there's a need for speculation, modelling and indirect evidence. It is this that opens the field up to "just-so stories" charge. There is also the potential for use of selective evidence - to simplistically support preferred moral positions, eg, tooth-and-claw v. cooperative vision of "human nature". However, this is not a problem that is peculiar to evolutionary psychology, it's a perenial problem for science, especially new fields. No doubt the situation will improve as things develop and there's a lot of baby in the bathwater of evolutionary psychology.

Young children and adults: intrinsically motivated to see others helped

This interesting piece from Tomasello and collaborators:

Young children help other people, but it is not clear why. In the current study, we found that 2-year-old children’s sympathetic arousal, as measured by relative changes in pupil dilation, is similar when they themselves help a person and when they see that person being helped by a third party (and sympathetic arousal in both cases is different from that when the person is not being helped at all). These results demonstrate that the intrinsic motivation for young children’s helping behavior does not require that they perform the behavior themselves and thus “get credit” for it, but rather requires only that the other person be helped. Thus, from an early age, humans seem to have genuine concern for the welfare of others.

And, Rand et al. use economic games with adult subjects to demonstrate that cooperation is intuitive, because cooperative heuristics are developed in daily life where cooperation is typically advantageous. This data adds to Kahneman's recent summary of evidence that much of human decision-making is governed by fast and automatic intuitions, rather than by slow, effortful thinking (see Kahneman, D. Thinking, Fast and Slow, Allen Lane, 2011). The Rand et al. abstract

Cooperation is central to human social behaviour. However, choosing to cooperate requires individuals to incur a personal cost to benefit others. Here we explore the cognitive basis of cooperative decision-making in humans using a dual-process framework. We ask whether people are predisposed towards selfishness, behaving cooperatively only through active self-control; or whether they are intuitively cooperative, with reflection and prospective reasoning favouring ‘rational’ self-interest. To investigate this issue, we perform ten studies using economic games. We find that across a range of experimental designs, subjects who reach their decisions more quickly are more cooperative. Furthermore, forcing subjects to decide quickly increases contributions, whereas instructing them to reflect and forcing them to decide slowly decreases contributions. Finally, an induction that primes subjects to trust their intuitions increases contributions compared with an induction that promotes greater reflection. To explain these results, we propose that cooperation is intuitive because cooperative heuristics are developed in daily life where cooperation is typically advantageous. We then validate predictions generated by this proposed mechanism. Our results provide convergent evidence that intuition supports cooperation in social dilemmas, and that reflection can undermine these cooperative impulses.

MRI of reading Jane Austen

Another totally annoying example of science by press release sans any reference to an original research article offers a glimpse at what looks like fascinating work, showing brain correlates of a kind of deep attention going with reading literature that is very different from the kind of deep attention that is focused on mastering a particular task.

In an innovative interdisciplinary study, neurobiological experts, radiologists and humanities scholars are working together to explore the relationship between reading, attention and distraction – by reading Jane Austen. Surprising preliminary results reveal a dramatic and unexpected increase in blood flow to regions of the brain beyond those responsible for "executive function," areas which would normally be associated with paying close attention to a task, such as reading, said Natalie Phillips, the literary scholar leading the project. During a series of ongoing experiments, functional magnetic resonance images track blood flow in the brains of subjects as they read excerpts of a Jane Austen novel. Experiment participants are first asked to leisurely skim a passage as they might do in a bookstore, and then to read more closely, as they would while studying for an exam. Phillips said the global increase in blood flow during close reading suggests that "paying attention to literary texts requires the coordination of multiple complex cognitive functions." Blood flow also increased during pleasure reading, but in different areas of the brain. Phillips suggested that each style of reading may create distinct patterns in the brain that are "far more complex than just work and play."

A commentary by Alan Jacobs on this work makes a further point, that we might do well to exercise various parts of our minds just as we do well to exercise various parts of our bodies. Otherwise we could end up like Charles Darwin, who felt that over time he had lost certain mental functions:

My mind seems to have become a kind of machine for grinding general laws out of large collections of facts, but why this should have caused the atrophy of that part of the brain alone, on which the higher tastes depend, I cannot conceive. A man with a mind more highly organised or better constituted than mine, would not, I suppose, have thus suffered; and if I had to live my life again, I would have made a rule to read some poetry and listen to some music at least once every week; for perhaps the parts of my brain now atrophied would thus have been kept active through use. The loss of these tastes is a loss of happiness, and may possibly be injurious to the intellect, and more probably to the moral character, by enfeebling the emotional part of our nature.

Rethinking sleep - brief wakeful resting boosts new memories over the long term.

Two recent articles point out that the prevailing notion that an eight hour chunk of sleep is required for optimum health and function is a relatively recent invention that doesn't take into account the usefulness of many varieties of sleep. Randall notes historical and contemporary evidence that other patterns are useful, and here is an abstract from Dewar et al. on how wakeful rest enhances long term consolidation of new memories:

A brief wakeful rest after new verbal learning enhances memory for several minutes. In the research reported here, we explored the possibility of extending this rest-induced memory enhancement over much longer periods. Participants were presented with two stories; one story was followed by a 10-min period of wakeful resting, and the other was followed by a 10-min period during which participants played a spot-the-difference game. In Experiment 1, wakeful resting led to significant enhancement of memory after a 15- to 30-min period and also after 7 days. In Experiment 2, this striking enhancement of memory 7 days after learning was demonstrated even when no retrievals were imposed in the interim. The degree to which people can remember prose after 7 days is significantly affected by the cognitive activity that they engage in shortly after new learning takes place. We propose that wakeful resting after new learning allows new memory traces to be consolidated better and hence to be retained for much longer.

Regulators of prosocial and empathetic behavior.

Two pieces in the September issue of Psychological Science deal with empathetic or prosocial behavior. Grant and Dutton make observations showing that prosocial behavior is boosted more by reflecting on giving than on receiving; and Lewis et al.'s experiments give a example of how stereotypes enhance empathetic accuracy.

Grant and Dutton:

Research shows that reflecting on benefits received can make people happier, but it is unclear whether or not such reflection makes them more helpful. Receiving benefits can promote prosocial behavior through reciprocity and positive affect, but these effects are often relationship-specific, short-lived, and complicated by ambivalent reactions. We propose that prosocial behavior is more likely when people reflect on being a benefactor to others, rather than a beneficiary. The experience of giving benefits may encourage prosocial behavior by increasing the salience and strength of one’s identity as a capable, caring contributor. In field and laboratory experiments, we found that participants who reflected about giving benefits voluntarily contributed more time to their university, and were more likely to donate money to natural-disaster victims, than were participants who reflected about receiving benefits. When it comes to reflection, giving may be more powerful than receiving as a driver of prosocial behavior.

Lewis et al.:

An ideal empathizer may attend to another person’s behavior in order to understand that person, but it is also possible that accurately understanding other people involves top-down strategies. We hypothesized that perceivers draw on stereotypes to infer other people’s thoughts and that stereotype use increases perceivers’ accuracy. In this study, perceivers (N = 161) inferred the thoughts of multiple targets. Inferences consistent with stereotypes for the targets’ group (new mothers) more accurately captured targets’ thoughts, particularly when actual thought content was also stereotypic. We also decomposed variance in empathic accuracy into thought, target, and perceiver variance. Although past research has frequently focused on variance between perceivers or targets (which assumes individual differences in the ability to understand other people or be understood, respectively), the current study showed that the most substantial variance was found within targets because of differences among thoughts.

Idle Minds - why are our brains so active when doing ‘nothing’?

Kerri Smith does a review on the resting or default activity of our brains, what is happening when we are not focused on anything in particular, but letting our minds just rest or wander at random: After initial observations in the mid-1990s showed that the brain never really takes a break,

...studies of the resting state in its own right began to emerge. A team led by Marcus Raichle characterized activity in one such network as the brain's default mode — what they considered its baseline setting. During tasks, default-mode activity actually dropped, coming back online when the brain was no longer focusing so intensely.

The default-mode network has been joined by dozens of other flavors of resting-state network — some of which resemble the circuitry that contributes to attention, vision, hearing or movement. They seem very similar across study participants but are also dynamic, changing over time.

One idea is that the brain is running several models of the world in the background, ready for one of them to turn into reality.

Raichle favors the idea that activity in the resting state helps the brain to stay organized. The connections between neurons are continually shifting as people age and learn, but humans maintain a sense of self throughout the upheaval. Spontaneous activity might play a part in maintaining that continuity. “Connections between neurons turn over in minutes, hours, days and weeks,...The structure of the brain will be different tomorrow but we will still remember who we are.” …the brain replays and consolidates new memories at any chance it gets — even when awake.

…perhaps the activity is part of the reshaping process, tweaking connections while we idle. Several teams have reported changes in resting connectivity after language and memory tasks and motor learning… suggesting that the brain is not only thinking about supper coming up, but it's also processing the recent past and converting some of that into long-term memories. The network changes are specific to the tasks performed.

Interpersonal closeness and brain social reward processing

I'm passing on a graphic from Vrticka's comments on recent work by Farei et al., who have observed brain activation patterns associated with sharing positive outcomes with a friends, that are also mirrored in high subjective ratings of excitement and high skin conductance responses during the same condition, reflecting increased biological arousal.

Illustration of the dynamic “push–pull” between social approach and aversion in the affective processing module of human social interaction. According to the phylogenetic perspective of social engagement and attachment proposed by Porges, human social functioning is determined by two opposite emotional brain systems representing positive (social approach; purple) versus negative (social aversion; blue) information. Whereas the social approach module mainly includes dopaminergic pathways (ventral tegmental area, striatum, ventral medial orbitofrontal cortex), as well as the pituitary/hypothalamus as the main site of oxytocin synthesis, the social aversion module operates through brain areas involved in fear/threat (amygdala), stress (hippocampus), disgust/empathy for pain/social rejection (insula and anterior cingulate cortex), and sadness (anterior temporal pole).

Here is the Farei et al. abstract:

Everyday goals and experiences are often shared with others who may hold different places within our social networks. We investigated whether the experience of sharing a reward differs with respect to social network. Twenty human participants played a card guessing game for shared monetary outcomes with three partners: a computer, a confederate (out of network), and a friend (in network). Participants subjectively rated the experience of sharing a reward more positively with their friends than the other partners. Neuroimaging results support participants' subjective reports, as ventral striatal BOLD responses were more robust when sharing monetary gains with a friend as compared to the confederate or computer, suggesting a higher value for sharing with an in-network partner. Interestingly, ratings of social closeness covaried with this activity, resulting in a significant partner × closeness interaction; exploratory analysis showed that only participants reporting higher levels of closeness demonstrated partner-related differences in striatal BOLD response. These results suggest that reward valuation in social contexts is sensitive to distinctions of social network, such that sharing positive experiences with in-network others may carry higher value.

Want to be unhappy? Trying to be happy will do it!

I'm finding the "Anxiety" topic in the Opinionator series at the NYTimes to be a real treat. This entry by British expatriate Ruth Whippman brings back memories of a my signing on several years ago to be a talking head neuroscience expert on the  California "Make Me Happy!" Radio Show (I don't think they were all that pleased with their dyspeptic guest!). Whippman notes the American obsession with, and anxiety over, being "happy", and contrasts this with the attitudes of more stoic Britishers:

Happiness in America has become the overachiever's ultimate trophy. A vicious trump card, it outranks professional achievement and social success, family, friendship and even love…this elusive MacGuffin is creating a nation of nervous wrecks. Despite being the richest nation on earth, the United States is, according to the World Health Organization, by a wide margin, also the most anxious, with nearly a third of Americans likely to suffer from an anxiety problem in their lifetime. America's precocious levels of anxiety are not just happening in spite of the great national happiness rat race, but also perhaps, because of it.

The British are generally uncomfortable around the subject, and as a rule, don't subscribe to the happy-ever-after. It's not that we don't want to be happy, it just seems somehow embarrassing to discuss it, and demeaning to chase it, like calling someone moments after a first date to ask them if they like you….Even the recent grand spectacle of the London 2012 Olympic Games told this tale. The opening ceremony, traditionally a sparklefest of perkiness, was, with its suffragist and trade unionists, mainly a celebration of dissent, or put less grandly, complaint…Our queen, despite the repeated presence of a stadium full of her subjects urging in song that she be both happy and glorious, could barely muster a smile, staring grimly through her eyeglasses and clutching her purse on her lap as if she might be mugged.

Cynicism is the British shtick. When happiness does come our way, it is entirely without effort, as unmeritocratic as a hereditary peerage. By contrast, in America, happiness is work. Intense, nail-biting work, slogged out in motivational seminars and therapy sessions, meditation retreats and airport bookstores. For the left there's yoga, for the right, there's Jesus. For no one is there respite…The people taking part in "happiness pursuits," as a rule, don't seem very happy…The happy person would be more likely to be off doing something fun, like sitting in the park drinking.

Happiness should be serendipitous, a by-product of a life well lived, and pursuing it in a vacuum doesn't really work. This is borne out by a series of slightly depressing statistics. The most likely customer of a self-help book is a person who has bought another self-help book in the last 18 months. The General Social Survey, a prominent data-based barometer of American society, shows little change in happiness levels since 1972, when such records began. Every year, with remarkable consistency, around 33 percent of Americans report that they are "very happy." It's a fair chunk, but a figure that remains surprisingly constant, untouched by the uptick in Eastern meditation or evangelical Christianity, by Tony Robbins or Gretchen Rubin or attachment parenting. For all the effort Americans are putting into happiness, they are not getting any happier. It is not surprising, then, that the search itself has become a source of anxiety.

So here's a bumper sticker: despite the glorious weather and spectacular landscape, the people of California are probably less happy and more anxious than the people of Grimsby. So they may as well stop trying so hard.

Just so stories about the evolution of our minds.

I want to point to a very nicely done review in The New Yorker by Anthony Gottlieb, who notes a number of recent books dealing with evolutionary psychology, but mainly comments on “Homo Mysterious: Evolutionary Puzzles of Human Nature” (Oxford), a new book by David Barash, a professor of psychology and biology at the University of Washington, Seattle. The main point of critics is that most evolutionary theories purporting to explain our sexual or other behaviors as evolved adaptations to conditions faced by our paleolithic ancestors have no more validity than Rudyard Kipling's "just so" stories about how the camel got his hump or the rhinoceros his wrinkly folds of skin. One clip from the review:

A review of the methods of evolutionary psychology, published last summer in a biology journal, underlined a point so simple that its implications are easily missed. To confirm any story about how the mind has been shaped, you need (among other things) to determine how people today actually think and behave, and to test rival accounts of how these traits function. Once you have done that, you will, in effect, have finished the job of explaining how the mind works. What life was really like in the Stone Age no longer matters. It doesn’t make any practical difference exactly how our traits became established. All that matters is that they are there.

Voting patterns: “I” value competence but “we” value social competence

(Chen et al. ask whether judgments of candidates' social competence—defined as the capacity for effective functioning in social interactions—are related to outcomes in an individualistic society (the United States) and a collectivist society (Taiwan). They replicate the earlier result that a judgment of competence does predict winners in the United States, as it does in Taiwan, and they find that judgments of social competence are also predictive, though only for elections in Taiwan. Their abstract:

This investigation distinguishes interpersonally oriented social competence from intrapersonally oriented competence. It examines the influence of voters' individualism and collectivism orientation in affecting the roles of these two dimensions in predicting electoral outcomes. Participants made judgments of personality traits based on inferences from faces of political candidates in the U.S. and Taiwan. Two social outcomes were examined: actual election results and voting support of the participants. With respect to actual electoral success, perceived competence is more important for the candidates in the U.S. than for those in Taiwan, whereas perceived social competence is more important for the candidates in Taiwan than for those in the U.S. With respect to subjective voting support, within cultural findings mirror those found cross-culturally. Competence is valued more among voters who are more individualistic, and social competence is valued more among voters who are more collectivistic. These results highlight important omissions in the social perception/judgment literature.

(excuse a techie note irrelevant to this post: I confirm the subscription of this blog to the Paperblog service under the username mdbownds)

Combat stress causes long term changes in brain connectivity.

Sobering results from Wingen et al.:

Prolonged stress can have long-lasting effects on cognition. Animal models suggest that deficits in executive functioning could result from alterations within the mesofrontal circuit. We investigated this hypothesis in soldiers before and after deployment to Afghanistan and a control group using functional and diffusion tensor imaging. Combat stress reduced midbrain activity and integrity, which was associated to compromised sustained attention. Long-term follow-up showed that the functional and structural changes had normalized within 1.5 y. In contrast, combat stress induced a persistent reduction in functional connectivity between the midbrain and prefrontal cortex. These results demonstrate that combat stress has adverse effects on the human mesofrontal circuit and suggests that these alterations are partially reversible.

Legend (click figure to enlarge) - Combat stress reduces functional connectivity of the midbrain with the lateral prefrontal cortex. The reduction from baseline to short-term follow-up is presented in blue. The persistent reduction from baseline to long-term follow-up at 1.5 y after military deployment is presented in green. The overlap between the short-term and long-term effects is presented in cyan.

A bit more expanded summary in their discussion:

These results show that the adverse effects of combat stress on sustained attention are related to functional and structural changes in the midbrain. These alterations normalize within 1.5 y in soldiers without psychiatric complaints, which may explain why long-term cognitive deficits following combat are mainly observed in soldiers with posttraumatic stress symptoms. In contrast to the reversible effects on the midbrain itself, its reduced interaction with the prefrontal cortex persists for at least 1.5 y. Taken together, these results suggest that the human brain can largely recover from the adverse effects of stress, supporting the view that neural plasticity in response to prolonged stress is adaptive. However, the results also reveal long-term changes within the mesofrontal network that may increase the vulnerability to subsequent stressors and lead to long-lasting cognitive deficits.

Male sex hormones alter the brain after exercise.

Numerous experiments have shown that exercise enhances our ability to remember and think, and causes formation of new nerve cells. A collaboration that includes McEwen's Laboratory of Neuroendocrinology at Rockefeller now shows (in rats) that brain (not gonadal) production of the testosterone derivative dihydroxtestosterone (DHT) is required for this effect. The amount of exercise required is quite mild (McEwen: "the equivalent of jogging at a pace at which someone could speak (or squeak) to a companion."). In castrated rats blocking the action of testosterone levels that have been enhanced by exercise (by blocking testosterone receptors in the brain) also blocks the formation of new nerve cells. The chemical details are given by their abstract:

Mild exercise activates hippocampal neurons through the glutamatergic pathway and also promotes adult hippocampal neurogenesis (AHN). We hypothesized that such exercise could enhance local androgen synthesis and cause AHN because hippocampal steroid synthesis is facilitated by activated neurons via N-methyl-D-aspartate receptors. Here we addressed this question using a mild-intense treadmill running model that has been shown to be a potent AHN stimulator. A mass-spectrometric analysis demonstrated that hippocampal dihydrotestosterone increased significantly, whereas testosterone levels did not increase significantly after 2 wk of treadmill running in both orchidectomized (ORX) and sham castrated (Sham) male rats. Furthermore, analysis of mRNA expression for the two isoforms of 5α-reductases (srd5a1, srd5a2) and for androgen receptor (AR) revealed that both increased in the hippocampus after exercise, even in ORX rats. All rats were injected twice with 5′-bromo-2′deoxyuridine (50 mg/kg body weight, i.p.) on the day before training. Mild exercise significantly increased AHN in both ORX and Sham rats. Moreover, the increase of doublecortin or 5′-bromo-2′deoxyuridine/NeuN-positive cells in ORX rats was blocked by s.c. flutamide, an AR antagonist. It was also found that application of an estrogen receptor antagonist, tamoxifen, did not suppress exercise-induced AHN. These results support the hypothesis that, in male animals, mild exercise enhances hippocampal synthesis of dihydrotestosterone and increases AHN via androgenenic mediation.

In commenting on this work in the NYTimes, Gretchen Reynolds raises an interesting question for women:

But while those findings may be salutary for men who are active and fit, or planning to become so, they seem potentially troubling for those of us without testes. If DHT is necessary for neurogenesis after exercise and women produce far less of it than men, do women gain less brain benefit from exercise than men?

On being nothing...

The "Opinionater" feature of the New York Times has "Anxiety" as one of its topics inviting online essays. I wanted to pass on a piece submitted by Brian Jay Stanley that notes how at every stage of our lives we desire to be noticed and affirmed by others, and in the absence of notice can easily become anxious, feeling insignificant and insubstantial. His last two paragraphs are a treat:

Society is adroit at disillusioning newcomers, and many self-assured children grow up to be bitter adults. But bitterness, instead of a form of disillusionment, is really the refusal to give up your childhood illusions of importance. Ignored instead of welcomed by the world, you fault the world as blind and evil in order not to fault yourself as naïve. Bitterness is a child’s coddling narcissism within the context of an adult’s harsh life. Instead, I know that the world only tramples me as a street crowd does an earthworm — not out of malice or stupidity, but because no one sees it. Thus my pain is not to feel wrongly slighted, but to feel rightly slighted.

There must be a Copernican revolution of the self. Instead of pointlessly cursing the sun to go around me, my chance of contentment is learning to orbit, being the world’s audience instead of demanding the world be mine. If the world is a stage, then everyone’s an extra, acting minor roles in simultaneous scenes in which no one has the lead. With so much happening, society is poorly made to satisfy pride, but well made to satisfy interest, if we will only let go of our vanity and join the swirl of activity.

Signing beforehand increases honesty.

Here is a fascinating simple study by Shu et al. Simply signing a statement of honesty at the top rather the bottom of a form makes you more honest. They outline the problem:

The annual tax gap between actual and claimed taxes due in the United States amounts to roughly $345 billion. The Internal Revenue Service estimates more than half this amount is due to individuals misrepresenting their income and deductions (1). Insurance is another domain burdened by the staggering cost of individual dishonesty; the Coalition Against Insurance Fraud estimated that the overall magnitude of insurance fraud in the United States totaled $80 billion in 2006 (2). The problem with curbing dishonesty in behaviors such as filing tax returns, submitting insurance claims, claiming business expenses or reporting billable hours is that they primarily rely on self-monitoring in lieu of external policing.

Here is their abstract:

Many written forms required by businesses and governments rely on honest reporting. Proof of honest intent is typically provided through signature at the end of, e.g., tax returns or insurance policy forms. Still, people sometimes cheat to advance their financial self-interests—at great costs to society. We test an easy-to-implement method to discourage dishonesty: signing at the beginning rather than at the end of a self-report, thereby reversing the order of the current practice. Using laboratory and field experiments, we find that signing before, rather than after, the opportunity to cheat makes ethics salient when they are needed most and significantly reduces dishonesty.

The experimental design used several different measures of cheating: self-reported earnings (income) on a math puzzles task wherein university participants could cheat for financial gain, self reported travel expenses to the laboratory (deductions) claimed on a tax return form on research earnings. Another experiment was done in the field with an insurance company in the southeastern United States asking some of their existing customers to report their odometer reading. They examined the effect of requiring the signature at the top of the form, the bottom, or the control of requiring no signature.