Cyclic variations in our vigilance

I had been unaware that our vigilance during a sustained attention task varies in a systematic way. Aue et al. have examined suggested rhythmic oscillations in the vigilance with which we maintain sustained attention by developing some continuous performance tasks:

...The current series of investigations sought to manipulate suggested periodicities of 1.5 and 5.2 min by altering task difficulty: tracking a white dot moving in a random pattern across an otherwise black computer display , administering caffeine, and testing on an ecologically valid task (simulated driving). Strong evidence of a 1.5 min periodicity was found across studies. Most participants did not demonstrate a 5.2 min periodicity. Moreover, the 1.5 min periodicity was resistant to task manipulations and appeared in similar levels across conditions in all experiments. These rhythms may be indicative of an endogenous system that modulates sustained attention in humans.

Low fat makes you happier?

Here is a curious fragment... Brinkworth et al. studied 106 obese people put on either a low fat or low carbohydrate diet for a year, doing psychological assessment tests during this period. Initially, shedding pounds put both groups in a better mood. But, in the low carbohydrate group this effect began to wear off after the first few weeks. Over 1 year, there was a favorable effect of an energy-restricted low fat diet compared with an isocaloric low carbohydrate diet on mood state and affect in overweight individuals, but both diets had similar effects on working memory and speed of information processing.

The sooner you can sleep, the better you learn.

Van Der Werf et al. investigate whether motor skill enhancement through prior observation requires sleep to follow the observation to consolidate the procedural memory:

Numerous studies have shown that sleep enhances memory for motor skills learned through practice. Motor skills can, however, also be learned through observation, a process possibly involving the mirror neuron system. We investigated whether motor skill enhancement through prior observation requires sleep to follow the observation, either immediately or after a delay, to consolidate the procedural memory. Sequence-specific fingertapping performance was tested in 64 healthy subjects in a balanced design. Electromyography verified absence of overt or subliminal hand muscle activations during observation. The results show that immediate sleep is necessary for the enhancement of a motor skill through prior observation. Immediate sleep improved the speed of subsequent performance by 22 ± 11% (mean ± SEM) (P = 0.04) and reduced the error rate by 42 ± 19% (P = 0.02). In contrast, no performance gains occurred if sleep was initiated more than 12 h after observation. A second study on 64 subjects ruled out explicit familiarity with the sequence or the spatiotemporal rhythm of the sequence to underlie performance improvements. The sleep-dependent observational motor learning enhancement is at least similar to that previously reported for implicit and declarative memory. The apparent prerequisite of observing real movements indicates that subjects transfer experience obtained through observation of movements to subsequent self-initiated movements, in the absence of practice. Moreover, the consolidation of this transfer requires an early sleep window. These findings could improve learning new motor skills in athletes and children, but also in patients having to remaster skills following stroke or injury.

Neurogenetics of remembering emotions past

It turns out that genetic makeup would determine how vididly Proust's narrator, on biting into a madeleine cake dipped in tea, would experience his emotional memories. Work by Rasch et al. suggests that individual differences in the ADRA2B gene that codes the α2B adrenoreceptor, which plays an important role in vasoconstriction and blood pressure regulation, is also related to brain activation patterns underlying heightened emotional recall:

Emotionally arousing events are typically well remembered, but there is a large interindividual variability for this phenomenon. We have recently shown that a functional deletion variant of ADRA2B, the gene encoding the α2b-adrenergic receptor, is related to enhanced emotional memory in healthy humans and enhanced traumatic memory in war victims. Here, we investigated the neural mechanisms of this effect in healthy participants by using fMRI. Carriers of the ADRA2B deletion variant exhibited increased activation of the amygdala during encoding of photographs with negative emotional valence compared with noncarriers of the deletion. Additionally, functional connectivity between amygdala and insula was significantly stronger in deletion carriers. The present findings indicate that the ADRA2B deletion variant is related to increased responsivity and connectivity of brain regions implicated in emotional memory.

Evolution of "the God gene"

Articles on a particular topic seem to come out in clusters. Shortly after doing yesterday's post on the origin of religions I see this article by Nicholas Wade in the NYTimes. He makes some further interesting points.

For atheists, it is not a particularly welcome thought that religion evolved because it conferred essential benefits on early human societies and their successors. If religion is a lifebelt, it is hard to portray it as useless...For believers, it may seem threatening to think that the mind has been shaped to believe in gods, since the actual existence of the divine may then seem less likely.

It is easier to see from hunter-gatherer societies how religion may have conferred compelling advantages in the struggle for survival. Their rituals emphasize not theology but intense communal dancing that may last through the night. The sustained rhythmic movement induces strong feelings of exaltation and emotional commitment to the group. Rituals also resolve quarrels and patch up the social fabric.

The ancestral human population of 50,000 years ago, to judge from living hunter-gatherers, would have lived in small, egalitarian groups without chiefs or headmen. Religion served them as an invisible government. It bound people together, committing them to put their community’s needs ahead of their own self-interest. For fear of divine punishment, people followed rules of self-restraint toward members of the community. Religion also emboldened them to give their lives in battle against outsiders. Groups fortified by religious belief would have prevailed over those that lacked it, and genes that prompted the mind toward ritual would eventually have become universal.

Could the evolutionary perspective on religion become the basis for some kind of detente between religion and science? Biologists and many atheists have a lot of respect for evolution and its workings, and if they regarded religious behavior as an evolved instinct they might see religion more favorably, or at least recognize its constructive roles. Religion is often blamed for its spectacular excesses, whether in promoting persecution or warfare, but gets less credit for its staple function of patching up the moral fabric of society. But perhaps it doesn’t deserve either blame or credit. If religion is seen as a means of generating social cohesion, it is a society and its leaders that put that cohesion to good or bad ends.

Cognitive science and the origin of religions

Elizabeth Culotta writes the 11th essay in Science's series in honor of the Year of Darwin, which explores the human propensity to believe in unseen deities. She describes a new field:'the cognitive science of religion', which draws on psychology, anthropology, and neuroscience to understand the mental building blocks of religious thought. Here are a few slightly edited clips from the essay:

...there remains a yawning gap between the material evidence of the archaeological record and the theoretical models of psychologists. Archaeological objects fall short of revealing our ancestors' minds while on the psychological side more evidence is needed.
...Many researchers take the use of symbols as a clue to budding spirituality. As far back as 100,000 years ago, people at the South African site of Blombos Cave incised pieces of ochre with geometric designs, creating the first widely recognized signs of symbolic behavior.

...While archaeologists trace the outward expressions of religious and symbolic behavior, another group of researchers is trying to trace more subtle building blocks of religious belief, seeking religion's roots in our minds.
...According to the emerging cognitive model of religion, we are so keenly attuned to the designs and desires of other people that we are hypersensitive to signs of "agents": thinking minds like our own... a "hypertrophy of social cognition" leads us to attribute random events or natural phenomena to the agency of another being.
...young children prefer "teleological," or purpose-driven, explanations rather than mechanical ones for natural phenomena...in several studies British and American children in first, second, and fourth grades were asked whether rocks are pointy because they are composed of small bits of material or in order to keep animals from sitting on them. The children preferred the teleological explanation. They give an animistic quality to the rock; it's protecting itself...we all from childhood have a bias to see the natural world as purposefully designed. It's a small step to suppose that the design has a designer.
...a hair-trigger agency detector could work with another sophisticated element of the human mind to make us prone to believe in gods: what's called theory of mind, or the understanding that another being has a mind with intentions, desires, and beliefs of its own.
...If you suspect that an agent was responsible for some mysterious event, it's a short step to thinking that the agent has a mind like your own. Higher order theory of mind enables you to represent mental states of beings not immediately or visibly present, and who could have a very different perspective than your own. That's what you need to have a rich representation of what it might be like to be a god. (It's also what is needed to have a functional religion, because people need to know that others share their beliefs.) As Darwin put it, humans developing religion "would naturally attribute to spirits the same passions, the same love of vengeance, or simplest form of justice, and the same affections which they themselves feel."
...Some fMRI studies lend support to this idea. When subjects in an fMRI scanner are asked to evaluate statements about God's emotions and relationships to humans, such as, "God is removed from the world" and "God is forgiving," the areas that light up, such as the inferior frontal gyrus on both sides of the brain, are also involved in theory of mind. This and other results argue against any special "god region" of the brain as some have suggested; rather, religious belief might co-opt widely distributed brain sectors, including many concerned with so-called theory of mind.

Many favor an additional class of explanations for why religion is so prominent in every culture: It promotes cooperative behavior among strangers and so creates stable groups. The hypothesis is that religion is actually adaptive: By encouraging helpful behavior, religious groups boost the biological survival and reproduction of their members. Adhering to strict behavioral rules may signal that a religion's members are strongly committed to the group and so will not seek a free ride, a perennial problem in cooperative groups

When the boss feels inadequate - power, incompetence, and aggression

Fast and Chen note that a startling 37% of American workers—roughly 54 million people—have been bullied at work, primarily having been sabotaged, yelled at, or belittled by their bosses . This statistic resonates with research showing a link between social power and aggression (i.e., acts aimed at harming other individuals, physically or otherwise). However, it also indicates that the link between power and aggression is not universal—after all, 63% of American workers have not been bullied at work. These observations raise an intriguing pair of questions: When are power holders most likely to behave aggressively, and why do they do so? Their abstract (PDF here):

When and why do power holders seek to harm other people? The present research examined the idea that aggression among the powerful is often the result of a threatened ego. Four studies demonstrated that individuals with power become aggressive when they feel incompetent in the domain of power. Regardless of whether power was measured in the workplace, manipulated via role recall, or assigned in the laboratory, it was associated with heightened aggression when paired with a lack of self-perceived competence. As hypothesized, this aggression appeared to be driven by ego threat: Aggressiveness was eliminated among participants whose sense of self-worth was boosted. Taken together, these findings suggest that (a) power paired with self-perceived incompetence leads to aggression, and (b) this aggressive response is driven by feelings of ego defensiveness. Implications for research on power, competence, and aggression are discussed.

Pig smarts

Broom et al. observe that domestic pigs can quickly learn how mirrors work and will use their understanding of reflected images to scope out their surroundings and find their food. Angier reviews this work and notes that:

Other researchers have found that pigs are brilliant at remembering where food stores are cached and how big each stash is relative to the rest. They’ve shown that Pig A can almost instantly learn to follow Pig B when the second pig shows signs of knowing where good food is stored, and that Pig B will try to deceive the pursuing pig and throw it off the trail so that Pig B can hog its food in peace.

One researcher looks

... at the pig as a great animal model for human lifestyle diseases...Pigs like to lie around, they like to drink if given the chance, they’ll smoke and watch TV.

Dreams as brain tuneups

Benedict Carey reviews the latest dream model suggested by Alan Hobson, whose work has stressed the more biological aspects of dreams and downplayed the idea that dreams have great psychological, psychoanalytic or Jungian archetypal significance. In general his models have suggested dreams to be confabulations generated in response to bottom up signals from the limbic system getting some regenerative exercise. His latest model suggests that REM sleep may constitute a protoconscious state, providing a virtual reality model of the world that is of functional use to the development and maintenance of waking consciousness. The main function of rapid-eye-movement sleep, or REM, when most dreaming occurs, is physiological. The brain is warming its circuits, anticipating the sights and sounds and emotions of waking.

Debate over the term Asperger's syndrome - continued

Autism expert Simon Baron-Cohen (cousin of the comic actor Sacha Baron-Cohen) weighs in on the debate that I mentioned in my 11/4/09 post over dropping the term Asperger's syndrome.

Part of the reason the diagnostic manual can move the boundaries and add or remove “mental disorders” so easily is that it focuses on surface appearances or behavior (symptoms) and is silent about causes. Symptoms can be arranged into groups in many ways, and there is no single right way to cluster them. Psychiatry is not at the stage of other branches of medicine, where a diagnostic category depends on a known biological mechanism. An example of where this does occur is Down syndrome, where surface appearances are irrelevant. Instead the cause — an extra copy of Chromosome 21 — is the sole determinant to obtain a diagnosis. Psychiatry, in contrast, does not yet have any diagnostic blood tests with which to reveal a biological mechanism.

..science hasn’t had a proper chance to test if there is a biological difference between Asperger syndrome and classic autism. My colleagues and I recently published the first candidate gene study of Asperger syndrome, which identified 14 genes associated with the condition.

We don’t yet know if Asperger syndrome is genetically identical or distinct from classic autism, but surely it makes scientific sense to wait until these two subgroups have been thoroughly tested before lumping them together in the diagnostic manual. I am the first to agree with the concept of an autistic spectrum, but there may be important differences between subgroups that the psychiatric association should not blur too hastily.

How you feel - the brain's bottom up and top down pathways

Ochsner et al use MRI to examine what is now becoming a common distinction, to consider the extent to which emotions arise via low-level processes that provide quick, bottom-up affective analyses of stimuli, versus high-level, top-down cognitive appraisal processes that draw upon stored knowledge. They did this by examining responses in trials with normatively aversive images (bottom-up trials) and also in novel trials in which participants cognitively interpreted neutral images as aversive (top-down trials). Here is the abstract, followed by a summary figure.

Emotions are generally thought to arise through the interaction of bottom-up and top-down processes. However, prior work has not delineated their relative contributions. In a sample of 20 females, we used functional magnetic resonance imaging to compare the neural correlates of negative emotions generated by the bottom-up perception of aversive images and by the top-down interpretation of neutral images as aversive. We found that (a) both types of responses activated the amygdala, although bottom-up responses did so more strongly; (b) bottom-up responses activated systems for attending to and encoding perceptual and affective stimulus properties, whereas top-down responses activated prefrontal regions that represent high-level cognitive interpretations; and (c) self-reported affect correlated with activity in the amygdala during bottom-up responding and with activity in the medial prefrontal cortex during top-down responding. These findings provide a neural foundation for emotion theories that posit multiple kinds of appraisal processes and help to clarify mechanisms underlying clinically relevant forms of emotion dysregulation.

Partner photographs can reduce experimentally induced pain

Master et al. make the not very suprising yet interesting observation that the known pain-attenuating effects of social support can be observed by merely activating the mental representation of a supportive other. Simply viewing a loved one's picture can have pain-attenuating effects, a finding which fits with social psychological research showing that being primed with a social construct is enough to activate associated mental representations and to bias behavior. Simple reminders of loved ones, apart from actual supportive social interactions, appear to be sufficient to engender feelings of support.

Evolution of the end of Origin of the Species

A fascinating compilation by Nickalls:

NOTE BOOK OF 1837

Astronomers might formerly have said that God foreordered each planet to move in its particular destiny. In the same manner God orders each animal created with certain forms in certain countries; but how much more simple and sublime [a] power—let attraction act according to certain law, such are inevitable consequences—let animals be created, then by the fixed laws of generation, such will be their successors. (1)

SKETCH OF 1842

There is a simple grandeur in the view of life with powers of growth, assimilation and reproduction, being originally breathed into matter under one or a few forms, and that whilst this our planet has gone circling on according to fixed laws, and land and water, in a cycle of change, have gone on replacing each other, that from so simple an origin, through the process of gradual selection of infinitesimal changes, endless forms most beautiful and most wonderful have been evolved. (2)

ESSAY OF 1844

There is a simple grandeur in this view of life with its several powers of growth, reproduction and of sensation, having been originally breathed into matter under a few forms, perhaps into only one, and that whilst this planet has gone cycling onwards according to the fixed laws of gravity and whilst land and water have gone on replacing each other—that from so simple an origin, through the selection of infinitesimal varieties, endless forms most beautiful and most wonderful have been evolved. (2)

ON THE ORIGIN OF SPECIES, 1859

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. (3)

References

• 1. F. Darwin, Ed., The Life and Letters of Charles Darwin (John Murray, London, 1887).
• 2. G. de Beer, Evolution by Natural Selection (Cambridge Univ. Press, Cambridge, 1958).
• 3. C. Darwin, On the Origin of Species by Natural Selection... (John Murray, London, 1859).

An anatomical signature for literacy

Here is some fascinating work from Carreiras et al. showing brain changes in adult Colombian guerrillas re-integrating into mainstream society and learning to read for the first time as adults:

Language is a uniquely human ability that evolved at some point in the roughly 6,000,000 years since human and chimpanzee lines diverged. Even in the most linguistically impoverished environments, children naturally develop sophisticated language systems. In contrast, reading is a learnt skill that does not develop without intensive tuition and practice. Learning to read is likely to involve ontogenic structural brain changes, but these are nearly impossible to isolate in children owing to concurrent biological, environmental and social maturational changes. In Colombia, guerrillas are re-integrating into mainstream society and learning to read for the first time as adults. This presents a unique opportunity to investigate how literacy changes the brain, without the maturational complications present in children. Here we compare structural brain scans from those who learnt to read as adults (late-literates) with those from a carefully matched set of illiterates. Late-literates had more white matter in the splenium of the corpus callosum and more grey matter in bilateral angular, dorsal occipital, middle temporal, left supramarginal and superior temporal gyri. The importance of these brain regions for skilled reading was investigated in early literates, who learnt to read as children. We found anatomical connections linking the left and right angular and dorsal occipital gyri through the area of the corpus callosum where white matter was higher in late-literates than in illiterates; that reading, relative to object naming, increased the interhemispheric functional connectivity between the left and right angular gyri; and that activation in the left angular gyrus exerts top-down modulation on information flow from the left dorsal occipital gyrus to the left supramarginal gyrus. These findings demonstrate how the regions identified in late-literates interact during reading, relative to object naming, in early literates.

A little fellatio goes a long way...

I can't resist passing on this item in ScienceNow:

Oral sex is surprisingly rare in the animal kingdom. Humans do it, of course. As do bonobos, our close relatives. But now researchers have observed the practice for the first time in a non-primate. Libiao Zhang, a biologist at Guangdong Entomological Institute in Guangzhou, China, and colleagues had been studying the mating behavior of the short-nosed fruit bat (Cynopterus sphinx), which is native to southeast Asia....Of the 20 observed mating bat pairs, 70% of the females performed fellatio on the males, the team reports online this week in PLoS ONE. The males never withdrew while being licked, and the authors found that the longer a female licked, the longer copulation lasted (for each second of licking, the female bats gained 6 seconds of copulation). The team speculates that licking helps maintain the male's erection, and that the saliva increases lubrication, both of which may prolong intercourse. In all, fellating females mated for an average of 4 minutes, twice as long as the other females.

Manipulating sex differences in romantic selectivity

From Finkel and Eastwick:

Men tend to be less selective than women when evaluating and pursuing potential romantic partners. The present experiment employed speed-dating procedures to test a novel explanation for this sex difference: The mere act of physically approaching a potential romantic partner (vs. being approached), a behavior that is more characteristic of men than of women, increases one's attraction to that partner. This hypothesis was supported in a sample of speed daters (N= 350) who attended a heterosexual event where either men (eight events) or women (seven events) rotated from one partner to the next while members of the other sex remained seated. Rotators were significantly less selective than were sitters, which meant that the tendency for men to be less selective than women at events where men rotated disappeared at events where women rotated. These effects were mediated by increased self-confidence among rotators relative to sitters.

Denialism

Janet Maslin offers a review of an interesting new book by Michael Specter: DENIALISM -How Irrational Thinking Hinders Scientific Progress, Harms the Planet and Threatens Our Lives. He explores the ways in which scientific information is misunderstood by a sizeable portion of the populace, struggling with change, that deflects reality to bask in more comfortable illusion. Here are a few clips:

In “The Organic Fetish,” a chapter that ably illustrates this book’s tactics and purpose, he uses Whole Foods as the apotheosis of a strain of magical thinking. First of all, he asks, what exactly is organic food? Is it more healthful than genetically engineered food or than food that has been harvested by robot-guided machinery rather than human hands? And are organic fertilizers more earth-friendly than synthetic ones? “There are no short answers to those questions (at least none that are true),” he says...And whatever the merits of organic farming for societies that can afford it, what happens in places where food, land or water are scarce? There is a case to be made for agricultural methods that make the most efficient use of new technologies, and thus for genetically engineered crops that produce increased yields. But these are widely derided as Frankenfoods. Their ability to scare people and trigger blanket resistance is one of this book’s foremost illustrations of denialism in action.

Of all the grenades lobbed by “Denialism,” the most explosive is aimed at Dr. Weil, the otherwise-sacrosanct avatar of New Age medicine. In the chapter called “The Era of Echinacea” Mr. Specter describes signing up for one of Dr. Weil’s customized mail-order regimens. “Dr. Weil, who argues that we need to reject the prevailing impersonal approach, reached out from cyberspace to recommend each of these pills wholeheartedly and specifically, just for me,” But Mr. Specter decided that the pills advocated by Dr. Weil fell into three categories: those that did no particular good, those that did some good but could interfere with the effects of prescribed medicines, and those that “seemed just plain dangerous.”..What bothered him more than Dr. Weil’s advice was Dr. Weil’s philosophy. “The idea that accruing data is simply one way to think about science has become a governing tenet of the alternative belief system,” Mr. Specter writes. And the additional idea that the evidence of experience is as important as the results of meticulous scientific testing is, in Mr. Specter’s view, one of the most dangerous forms of denialism, especially when it comes from a figure of Dr. Weil’s stature. As “Denialism” puts it: “It is much easier to dismiss a complete kook — there are thousands to choose from — than a respected physician who, interspersed with disquisitions about life forces and energy fields, occasionally has something useful to say.”

Neural correlates of musical consonance and dissonance

Bidelman and Krishnan make interesting observations suggesting that very fundamental low level sensory processing at the level of the brain stem may determine what sound intervals we find consonant or dissonant:

Consonant and dissonant pitch relationships in music provide the foundation of melody and harmony, the building blocks of Western tonal music. We hypothesized that phase-locked neural activity within the brainstem may preserve information relevant to these important perceptual attributes of music. To this end, we measured brainstem frequency-following responses (FFRs) from nonmusicians in response to the dichotic presentation of nine musical intervals that varied in their degree of consonance and dissonance. Neural pitch salience was computed for each response using temporally based autocorrelation and harmonic pitch sieve analyses. Brainstem responses to consonant intervals were more robust and yielded stronger pitch salience than those to dissonant intervals. In addition, the ordering of neural pitch salience across musical intervals followed the hierarchical arrangement of pitch stipulated by Western music theory. Finally, pitch salience derived from neural data showed high correspondence with behavioral consonance judgments (r = 0.81). These results suggest that brainstem neural mechanisms mediating pitch processing show preferential encoding of consonant musical relationships and, furthermore, preserve the hierarchical pitch relationships found in music, even for individuals without formal musical training. We infer that the basic pitch relationships governing music may be rooted in low-level sensory processing and that an encoding scheme that favors consonant pitch relationships may be one reason why such intervals are preferred behaviorally.

Can you believe...? The perfect product

Starting to read this piece by Miller and Stone at first left me speechless with incredulity. This would appear to be the perfect scam (or business model) - getting people to pay real money for a product that doesn't exist. We're talking about virtual goods with a marginal cost of zero and a profit margin of 100%. The virtual goods are things like swords and spells in virtual fantasy realms, or...

In Restaurant City, a game by Playfish on Facebook, 18 million active users manage their own cafe and stock it with virtual casseroles and cakes. In Zynga’s game FarmVille, 62 million agrarian dreamers cultivate a farm, plant squash seeds and harvest their crops with tractors. (the figure shows a consumer with her cat, Demon Baby, bought for the game Pet Society.)

Crazy? Maybe not:

...strong — and somewhat rational — motives are at work. Users of social networks can buy one another gifts, like images of flowers and birthday cakes, typically for a dollar each. Facebook recently expanded its gift store to allow other companies to list their virtual wares, like greeting cards...“It’s not about the good itself, it’s about the underlying human emotion or desire,” said Moshe Koyfman, a principal at Spark Capital, which has invested in two virtual-goods start-ups. “The recipient knows the person took time, picked something meaningful and spent money on it.”

Some game fans claim that in some cases, virtual goods can be better than the real thing. Jamie Kwong, a 13-year-old in Altadena, Calif., spends hours a week on a “paper doll” site called Stardoll, buying dresses and handbags. She created Juillet606, with brown eyes and hair to match her own. Unlike the actual paper dolls she used to play with, the tabs do not rip off....“With Stardoll it all stays on there, my brother can’t get on it, and everything is good,” she said.

Maybe we should view this as the ultimate "Green" consumer product - money spent with zero environmental impact (if you accept that the energy sucking infrastructure of the internet would be there anyway).

Genes that influence our adaptability to changing rewards

Krugel et al show that a genetic change that leads to replacement of the amino acid valine with methionine in an enzyme regulating brain dopamine levels alters the flexible adaptation of reward based learning.

We show a behavioral advantage for the phylogenetically ancestral Val/Val genotype in an instrumental reversal learning task that requires rapid and flexible adaptation of decisions to changing reward contingencies in a dynamic environment...we discovered that a higher and more flexible learning rate underlies the advantage of the Val/Val genotype. Model-based fMRI analysis revealed that greater and more differentiated striatal fMRI responses to prediction errors reflect this advantage on the neurobiological level. Learning rate-dependent changes in effective connectivity between the striatum and prefrontal cortex were greater in the Val/Val than Met/Met genotype, suggesting that the advantage results from a downstream effect of the prefrontal cortex that is presumably mediated by differences in dopamine metabolism. These results show a critical role of dopamine in processing the weight a particular prediction error has on the expectation updating for the next decision.