Brain correlates of choice-induced preference change.

In an interesting article, Izuma et al. call classical cognitive dissonance theory into question. Their observations suggest that our preference for our choice between two equally desirable items is established by the act of choosing, not by a subsequent reduction of our preference for one of them. In other words, the mere act of rejecting favorite goods actually reduces preferences for them. Their abstract gives a clear summary of their observations:

According to many modern economic theories, actions simply reflect an individual's preferences, whereas a psychological phenomenon called “cognitive dissonance” claims that actions can also create preference. Cognitive dissonance theory states that after making a difficult choice between two equally preferred items, the act of rejecting a favorite item induces an uncomfortable feeling (cognitive dissonance), which in turn motivates individuals to change their preferences to match their prior decision (i.e., reducing preference for rejected items). Recently, however, Chen and Risen [Chen K, Risen J (2010) J Pers Soc Psychol 99:573–594] pointed out a serious methodological problem, which casts a doubt on the very existence of this choice-induced preference change as studied over the past 50 y. Here, using a proper control condition and two measures of preferences (self-report and brain activity), we found that the mere act of making a choice can change self-report preference as well as its neural representation (i.e., striatum activity), thus providing strong evidence for choice-induced preference change. Furthermore, our data indicate that the anterior cingulate cortex and dorsolateral prefrontal cortex tracked the degree of cognitive dissonance on a trial-by-trial basis. Our findings provide important insights into the neural basis of how actions can alter an individual's preferences.

Influence of language on perception

Landau et al. show that hearing recorded sentences describing faces (versus places) enhances a subsequent electrophysiological marker of brain responses to pictures of faces, while seeing pictures of faces diminishes the subsequent responses. This shows that language influences early stages of visual processing.

We examined the effect of linguistic comprehension on early perceptual encoding in a series of electrophysiological and behavioral studies on humans. Using the fact that pictures of faces elicit a robust and reliable evoked response that peaks at ~170 ms after stimulus onset (N170), we measured the N170 to faces that were preceded by primes that referred to either faces or scenes. When the primes were auditory sentences, the magnitude of the N170 was larger when the face stimuli were preceded by sentences describing faces compared to sentences describing scenes. In contrast, when the primes were visual, the N170 was smaller after visual primes of faces compared to visual primes of scenes. Similar opposing effects of linguistic and visual primes were also observed in a reaction time experiment in which participants judged the gender of faces. These results provide novel evidence of the influence of language on early perceptual processes and suggest a surprising mechanistic description of this interaction: linguistic primes produce content-specific interference on subsequent visual processing. This interference may be a consequence of the natural statistics of language and vision given that linguistic content is generally uncorrelated with the contents of perception.

The wolfpack effect.

An interesting piece of work from Gao et al. showing how the perception of animacy influences our interactive behavior.

Imagine a pack of predators stalking their prey. The predators may not always move directly toward their target (e.g., when circling around it), but they may be consistently facing toward it. The human visual system appears to be extremely sensitive to such situations, even in displays involving simple shapes. We demonstrate this by introducing the wolfpack effect, which is found when several randomly moving, oriented shapes (darts, or discs with “eyes”) consistently point toward a moving disc. Despite the randomness of the shapes’ movement, they seem to interact with the disc—as if they are collectively pursuing it. This impairs performance in interactive tasks (including detection of actual pursuit), and observers selectively avoid such shapes when moving a disc through the display themselves. These and other results reveal that the wolfpack effect is a novel “social” cue to perceived animacy. And, whereas previous work has focused on the causes of perceived animacy, these results demonstrate its effects, showing how it irresistibly and implicitly shapes visual performance and interactive behavior.

Sample display (a) and manipulations (b–e) from the first experiment. The task was to detect whether one shape (the wolf) was chasing another (the sheep). Arrows indicate motion and were not present in the displays. In the wolfpack condition (a, b), all darts stayed oriented toward the task-irrelevant green square, regardless of their motion directions. This condition generated the wolfpack effect. In the perpendicular condition (c), each dart was always oriented orthogonally to the square. In the match condition (d), each dart was always oriented in the direction in which it was moving at that moment. And in the disc condition (e), the objects had no visible orientation.

A contrarian view of energy prospects.

John Tierney describes a wager he made in 2005 with Matthew Simmons, who bet $5,000 that the price of oil, then about $65 a barrel, would more than triple in the next five years, so that the average price of oil over the course of 2010 would be at least $200 a barrel in 2005 dollars....The average for 2010 has been just under $80, which is the equivalent of about $71 in 2005 dollars — a little higher than the $65 at the time of the bet, but far below the $200 threshold set by Mr. Simmons. (Tierney's mentor was the economist Julian L. Simon, a leader of the Cornucopians, optimists who believed there would always be abundant supplies of energy and other resources. Simon won a bet in the 1980s with Paul Ehrlich and two natural resources experts over the prices of five metals.) What happened to the grim predictions of declining oil reserves and rising prices? Perhaps there has been a temporary respite (which unfortunately will not help alternative energy efforts):

Giant new oil fields have been discovered off the coasts of Africa and Brazil. The new oil sands projects in Canada now supply more oil to the United States than Saudi Arabia does. Oil production in the United States increased last year, and the Department of Energy projects further increases over the next two decades...The really good news is the discovery of vast quantities of natural gas. It’s now selling for less than half of what it was five years ago. There’s so much available that the Energy Department is predicting low prices for gas and electricity for the next quarter-century. Lobbyists for wind farms, once again, have been telling Washington that the “sustainable energy” industry can’t sustain itself without further subsidies...As gas replaces dirtier fossil fuels, the rise in greenhouse gas emissions will be tempered, according to the Department of Energy. It projects that no new coal power plants will be built, and that the level of carbon dioxide emissions in the United States will remain below the rate of 2005 for the next 15 years even if no new restrictions are imposed.

Maybe something unexpected will change these happy trends, but for now I’d say that Julian Simon’s advice remains as good as ever. You can always make news with doomsday predictions, but you can usually make money betting against them.

New brain circuits form online during rapid learning

Shtyrov et. al. show that after just 14 minutes of learning exposure to a new word, presentations of this word cause increased responses in the language cortex, reflecting rapid mapping of new word forms onto neural representations.

Humans are unique in developing large lexicons as their communication tool. To achieve this, they are able to learn new words rapidly. However, neural bases of this rapid learning, which may be an expression of a more general cognitive mechanism, are not yet understood. To address this, we exposed our subjects to familiar words and novel spoken stimuli in a short passive perceptual learning session and compared automatic brain responses to these items throughout the learning exposure. Initially, we found enhanced activity for known words, indexing the ignition of their underlying memory traces. However, just after 14 min of learning exposure, the novel items exhibited a significant increase in response magnitude matching in size with that to real words. This activation increase, as we would like to propose, reflects rapid mapping of new word forms onto neural representations. Similar to familiar words, the neural activity subserving rapid learning of new word forms was generated in the left-perisylvian language cortex, especially anterior superior-temporal areas. This first report of a neural correlate of rapid learning suggests that our brain may effectively form new neuronal circuits online as it gets exposed to novel patterns in the sensory input. Understanding such fast learning is key to the neurobiological explanation of the human language faculty and learning mechanisms in general.

Paying the price for a longer life.

A brief article by Bakalar notes a study by Crimmins et al.

...people live longer not because they are less likely to get sick, but because they survive longer with disease....As a result, a 20-year-old man today can expect to live about a year longer than a 20-year-old in 1998, but will spend 1.2 years more with a disease, and 2 more years unable to function normally.

Placebo pills work without deception

Kaptchuk et al. show that placebos administered without deception may be an effective treatment for irritable bowel syndrome. From Bakalar's summary:

They explained to all that a placebo was an inert substance, like a sugar pill, that had been found to “produce significant improvement in I.B.S. symptoms through mind-body self-healing processes.” The patients, all treated with the same attention, warmth and empathy by the researchers, were then randomly assigned to get the pill or not...At the end of three weeks, they tested all the patients with questionnaires assessing the level of their pain and other symptoms. The patients given the sugar pill — in a bottle clearly marked “placebo” — reported significantly better pain relief and greater reduction in the severity of other symptoms than those who got no pill.

A weakness of the study is that because the outcome measure is so subjective, placebo patients may have exaggerated their improvement to please the researchers.

English and Mandarin speakers think about time differently.

I pass on this abstract from Boroditsky et al., and a few clips from the article:

Time is a fundamental domain of experience. In this paper we ask whether aspects of language and culture affect how people think about this domain. Specifically, we consider whether English and Mandarin speakers think about time differently. We review all of the available evidence both for and against this hypothesis, and report new data that further support and refine it. The results demonstrate that English and Mandarin speakers do think about time differently. As predicted by patterns in language, Mandarin speakers are more likely than English speakers to think about time vertically (with earlier time-points above and later time-points below).

From their text:

Both English and Mandarin use horizontal front/back spatial terms to talk about time. In English, we can look forward to the good times ahead, or think back to travails past and be glad they are behind us. In Mandarin, front/back spatial metaphors for time are also common. For example,  Mandarin speakers use the spatial morphemes qián (‘‘front”) and hòu (‘‘back”) to talk about time...Unlike English speakers, Mandarin speakers also systematically and frequently use vertical metaphors. The spatial morphemes shàng (‘‘up”) and xià (‘‘down”) are used to talk about the order of events, weeks, months, semesters, and more. Earlier events are said to be shàng or ‘‘up”, and later events are said to be xià or ‘‘down”.  For example, “shàng ge yuè” is last (or previous) month, and “xià ge yuè” is next (or following) month...This difference between the two languages offers the prediction that Mandarin speakers would be more likely to conceive of time vertically than would English speakers.

In the experimental paradigm, participants made temporal judgments following horizontal or vertical spatial primes. On each trial, participants first answered several questions about the spatial relationship between two objects (arranged either horizontally or vertically on a computer screen), and then answered a question about time (e.g., March comes earlier than April; TRUE or FALSE). Participants’ response times to the target question about time following either the horizontal or vertical primes were the measure of interest.

The basic finding was that both groups organize time on the left-to-right axis with earlier events on the left, a pattern consistent with writing direction. But, Mandarin speakers also show evidence of vertical representations of time, with earlier events represented further up. English speakers showed no evidence of such a representation.

You've got to have (150) friends...

The post title is the title of a brief essay by Robin Dunbar, who is best known for his work documenting, for a large number of animal species,  the relationship between brain size and social group size (they get larger together.)   His curve predicts that the optimal group size for humans is about 150.  That is what is observed over a large number of hunter-gatherer and aboriginal human species across the world,  and (his article contends) is an evolved biological/psychological limit that operates even in a world of facebook that permits thousands of "friends." Some clips:

The developers at Facebook overlooked one of the crucial components in the complicated business of how we create relationships: our minds...Put simply, our minds are not designed to allow us to have more than a very limited number of people in our social world. The emotional and psychological investments that a close relationship requires are considerable, and the emotional capital we have available is limited...Indeed, no matter what Facebook allows us to do, I have found that most of us can maintain only around 150 meaningful relationships, online and off — what has become known as Dunbar’s number. Yes, you can “friend” 500, 1,000, even 5,000 people with your Facebook page, but all save the core 150 are mere voyeurs looking into your daily life — a fact incorporated into the new social networking site Path, which limits the number of friends you can have to 50.

Until relatively recently, almost everyone on earth lived in small, rural, densely interconnected communities, where our 150 friends all knew one another...the social and economic mobility of the past century has worn away at that interconnectedness. As we move around the country and across continents, we collect disparate pockets of friends, so that our list of 150 consists of a half-dozen subsets of people who barely know of one another’s existence...as we move around, though, we can lose touch with even our closest friends. Emotional closeness declines by around 15 percent a year in the absence of face-to-face contact, so that in five years someone can go from being an intimate acquaintance to the most distant outer layer of your 150 friends.

Facebook and other social networking sites allow us to keep up with friendships that would otherwise rapidly wither away. And they do something else that’s probably more important, if much less obvious: they allow us to reintegrate our networks so that, rather than having several disconnected subsets of friends, we can rebuild, albeit virtually, the kind of old rural communities where everyone knew everyone else. Welcome to the electronic village.

The science of cities.

I've been meaning to point out an interesting article by Jonah Lehrer that focuses on the work of 70-year old physicist Geoffrey West, who decided to turn his attention to discerning whether the cities that containing an ever increasing fraction of the world's population (82% of the people in the U.S. live in cities) follow discernible patterns and laws. Some edited clips:

Knowing the population of a metropolitan area in a given country allows one to estimate, with approximately 85 percent accuracy, its average income and the dimensions of its sewer system. These are the laws, they say, that automatically emerge whenever people “agglomerate,” cramming themselves into apartment buildings and subway cars. It doesn’t matter if the place is Manhattan or Manhattan, Kan.: the urban patterns remain the same...the real purpose of cities, and the reason cities keep on growing, is their ability to create massive economies of scale, just as big animals do. After analyzing the first sets of city data — the physicists began with infrastructure and consumption statistics — they concluded that cities looked a lot like elephants. In city after city, the indicators of urban “metabolism,” like the number of gas stations or the total surface area of roads, showed that when a city doubles in size, it requires an increase in resources of only 85 percent...This straightforward observation has some surprising implications. It suggests, for instance, that modern cities are the real centers of sustainability. According to the data, people who live in densely populated places require less heat in the winter and need fewer miles of asphalt per capita.

People, however, do not go to cities because they are more efficient, they go because their are more social and commercial interactions. West and colleagues were able to quantify Jane Jacob's points in her famous book “The Death and Life of Great American Cities.”

...whenever a city doubles in size, every measure of economic activity, from construction spending to the amount of bank deposits, increases by approximately 15 percent per capita (It also experiences a 15 percent per capita increase in violent crimes, traffic and AIDS cases). It doesn’t matter how big the city is; the law remains the same...everything that’s related to the social network goes up by the same percentage.

Listening to your heart

Dunn et al. try to evaluate how sensing feedback from the body influences thought and feeling. Some edited clips of background, and their results:

Some metaphorical expressions that are used daily, such as “brokenhearted” or “gut feelings,” reflect the common belief that feelings and cognitions are partly grounded in bodily responses. This idea is reflected in early philosophical writings about embodiment (e.g., Descartes, 1649/1989) and was introduced to experimental psychology by William James (1884), who asserted that perception of changes in the body “as they occur is the emotion” (pp. 189–190). Since then, there has been considerable debate about the extent to which feelings and cognitions are in fact embodied. Much of this discussion has focused on emotion experience and decision making. Schachter and Singer modified Jamesian theory to argue that emotion experience is a product of the cognitive appraisal of bodily arousal. The somatic marker hypothesis of Damasio proposes that emotional biasing signals emerging from the body influence intuitive decision making. These models remain controversial, and critics argue that bodily responses occur relatively late in the information-processing chain and are therefore best viewed as a consequence, rather than the cause, of cognitive-affective activity.

...A central but untested prediction of many of these proposals is that how well individuals can perceive subtle bodily changes (interoception) determines the strength of the relationship between bodily reactions and cognitive-affective processing. In a first study we demonstrated that the more accurately participants could track their heartbeat, the stronger the observed link between their heart rate reactions and their subjective arousal (but not valence) ratings of emotional images. (In other words, the more strongly these autonomic changes are felt, the more they are associated with arousal experience.) These results offer strong support for Jamesian bodily feedback theories.

In a second study, we found that increasing interoception ability either helped or hindered adaptive intuitive decision making, depending on whether the anticipatory bodily signals generated favored advantageous or disadvantageous choices. These findings identify both the generation and the perception of bodily responses as pivotal sources of variability in emotion experience and intuition, and offer strong supporting evidence for bodily feedback theories, suggesting that cognitive-affective processing does in significant part relate to “following the heart.” Our findings agree with those of other studies showing that an absence of emotion following frontal head injury can in some circumstances lead to superior decision making and with claims that elevated interoceptive awareness may maintain conditions such as anxiety.

Deric's MindBlog for smartphones

I use Google's Blogger to publish MindBlog, and they have just added a nice new tweak.

We realize that more and more users are accessing the web on smartphones, and we want to make sure that blogs still look nice when viewed on these smaller screens. We’ve put a lot of work into creating a mobile version of BlogSpot, which will automatically detect if a blog is accessed on a smartphone and then display a mobile-optimized version.

I have enabled this feature, so now if you go to mindblog.dericbownds.net using your iPhone or other smartphone,  you see this new format. 

The dark side of inflammation

Couzin-Frankel does an interesting piece in the News section of the Dec. 17 issue of Science, consonant with my opinion that inflammatory processes are one of the main issues in aging. The abstract:

Not long ago, inflammation had a clear role: It was a sidekick to the body's healers, briefly setting in as immune cells rebuilt tissue damaged by trauma or infection. Today, that's an afterthought. Inflammation has hit the big time. Over the past decade, it has become widely accepted that inflammation is a driving force behind chronic diseases that will kill nearly all of us. Cancer. Diabetes and obesity. Alzheimer's disease. Atherosclerosis. Here, inflammation wears a grim mask, shedding its redeeming features and making sick people sicker.

A growing body of evidence suggests that C-reactive protein (CRP), a molecular marker for inflammation, may be as crucial as cholesterol in assessing risk of heart attack. Macrophages, the white blood cells that are a hallmark of inflammation, appear around fatty plaques that build up in the arteries in atherosclerosis, infiltrate fat tissue in obesity, surround cancer cells to stimulate circulation and coax them along, help to kill neurons in neurodegenerative diseases such as Alzheimer's and Parkinson's, and promote two components of type 2 diabetes: insulin resistance and the death of pancreatic beta cells that produce insulin. Anti-inflammatory drugs (that suppresses action of proinflammatory cytokines released by immune cells)  have been shown in several cases to retard disease progression.

Google's body browser

I've been enjoying playing a bit with Google's new 3-D body browser that lets you proceed through body layers (muscles,organs, bones, circulatory and nervous systems), clicking on a part or area to see it outlined and identified. It is still very much under development, with the nervous system and brain yet to be fully engaged. When it's further along, it should be a tremendously convenient look up tool. You need a web browser that supports WebGL, such as Chrome or Firefox 4 Beta. You can share the exact scene you are viewing by copying and pasting the URL (the sciatic nerve, for example).

Why diets fail.

Pankevich et al. offer observations that might explain why weight lost during an effective diet is usually regained - dieting makes the brain more sensitive to stress and the rewards of high-fat, high-calorie treats. These brain changes last long after the diet is over and prod otherwise healthy individuals to binge eat under pressure. Part of the abstract:

Long-term weight management by dieting has a high failure rate. Pharmacological targets have focused on appetite reduction, although less is understood as to the potential contributions of the stress state during dieting in long-term behavioral modification. In a mouse model of moderate caloric restriction in which a 10–15% weight loss similar to human dieting is produced, we examined physiological and behavioral stress measures. After 3 weeks of restriction, mice showed significant increases in immobile time in a tail suspension test and stress-induced corticosterone levels. Increased stress was associated with brain region-specific alterations of corticotropin-releasing factor expression and promoter methylation, changes that were not normalized with refeeding. Similar outcomes were produced by high-fat diet withdrawal, an additional component of human dieting. In examination of long-term behavioral consequences, previously restricted mice showed a significant increase in binge eating of a palatable high-fat food during stress exposure...In humans, such changes would be expected to reduce treatment success by promoting behaviors resulting in weight regain, and suggest that management of stress during dieting may be beneficial in long-term maintenance.

Sigh....

Coming upon cheerful news like the following makes me want to dig a hole, get in it, and pull it in after myself....

40 Percent Of Americans Still Believe In Creationism
Creationists And Climate Deniers Take On Teaching Climate Science In Schools

Regulation of distress better with thicker prefrontal cortex.

Ventral prefrontal cortex activity correlates with suppression of amygdala reactivity to emotionally challenging stimuli, presumably reflecting higher-order cognitive evaluation of negative stimuli being brought into play. (The amygdala influences a broad range of physiological and behavioral responses associated with emotion, with the left amygdala being particularly responsive to negative facial expressions.) Foland-Ross et al. have now shown that prefrontal grey matter (nerve cell containing cortical layer) thickness inversely correlates with amygdala reactivity. Greater ventromedial prefrontal cortical gray matter thickness was associated with greater reduction of activation in the left amygdala during affect labeling, a cognitive task that had previously been shown to dampen amygdala response.

In other words, if you have a thicker layer of prefrontal nerve cells, you might be less prone to emotional upset from unpleasant stimuli.

Out of our brains - extended mind continues

As a followup to my Nov. 3 post on critiques of Andy Clark's extended mind ideas (which drew 20 comments) I wanted to pass on this further Clark commentary and a sequel, pointed out to me by a loyal MindBlog reader, in which Clark tries to clarify his ideas.

Reducing depression with light stimulation of medial prefrontal cortex

In mice, to be sure.....Brain imaging and direct brain stimulation have implicated the prefrontal cortex in clinical depression in humans and mice, and now a study by Covington et al. confirms in both that suppression of gene activities associated with nerve activity in medial prefrontal cortex are associated with depressive behavior. In mice they used a genetic trick to introduce light activated channel proteins into nerve cells membranes in this area, and found that light stimulation which enhanced nerve activity had potent antidepressant-like effects. Here is their abstract:

Brain stimulation and imaging studies in humans have highlighted a key role for the prefrontal cortex in clinical depression; however, it remains unknown whether excitation or inhibition of prefrontal cortical neuronal activity is associated with antidepressant responses. Here, we examined cellular indicators of functional activity, including the immediate early genes (IEGs) zif268 (egr1), c-fos, and arc, in the prefrontal cortex of clinically depressed humans obtained postmortem. We also examined these genes in the ventral portion of the medial prefrontal cortex (mPFC) of mice after chronic social defeat stress, a mouse model of depression. In addition, we used viral vectors to overexpress channel rhodopsin 2 (a light-activated cation channel) in mouse mPFC to optogenetically drive "burst" patterns of cortical firing in vivo and examine the behavioral consequences. Prefrontal cortical tissue derived from clinically depressed humans displayed significant reductions in IEG expression, consistent with a deficit in neuronal activity within this brain region. Mice subjected to chronic social defeat stress exhibited similar reductions in levels of IEG expression in mPFC. Interestingly, some of these changes were not observed in defeated mice that escape the deleterious consequences of the stress, i.e., resilient animals. In those mice that expressed a strong depressive-like phenotype, i.e., susceptible animals, optogenetic stimulation of mPFC exerted potent antidepressant-like effects, without affecting general locomotor activity, anxiety-like behaviors, or social memory. These results indicate that the activity of the mPFC is a key determinant of depression-like behavior, as well as antidepressant responses.

Time, space, and number - evolved brain computations

Dehaene and Brannon introduce a special (and open access) issue of Trends in Cognitive Science on Time, space, and number.

What do the representations of space, time and number share that might justify their joint presence in a special issue of TICS? In his Critique of Pure Reason, Immanuel Kant famously argued that they provide ‘a priori intuitions’ that precede and structure how humans experience the environment. Indeed, these concepts are so basic to any understanding of the external world that it is hard to imagine how any animal species could survive without having mechanisms for spatial navigation, temporal orienting (e.g. time-stamped memories) and elementary numerical computations (e.g. choosing the food patch with the largest expected return). In the course of their evolution, humans and many other animal species might have internalized basic codes and operations that are isomorphic to the physical and arithmetic laws that govern the interaction of objects in the external world. The articles in this special issue all support this point of view: from grid cells to number neurons, the richness and variety of mechanisms by which animals and humans, including infants, can represent the dimensions of space, time and number is bewildering and suggests evolutionary processes and neural mechanisms by which Kantian intuitions might universally arise.