Oxytocin makes people trusting, but not gullible.

Mikolajczak et al. demonstrate that oxytocin (OT) is not the magical “trust elixir” described in the news, on the Internet, or even by some influential researchers. They design experiments to show that it does not make people indiscriminately prosocial (trusting to a fault). They used a customized version of the trust game that manipulated partners’ trustworthiness and measured participants’ investment in each partner. They found higher investment by participants who received a nasal OT spray than by control participants, unless there were cues that a partner might not be trustworthy. They also observed a significant effect of OT when the partner was a computer suggesting that OT’s effect may be primarily moderated not by the human versus nonhuman nature of the partner, but rather by the perceived risk inherent to the interaction. In case you are interested, here is their description of the setup:

Each participant assumed the role of investor and could transfer money to a “trustee,” in whose hands the funds would triple. The trustee would then transfer all the money, part of it, or none of it back to the investor. If the investor entrusted the trustee with all of his money, he could maximize his profits if the trustee was reliable and fair. Conversely, he could lose everything if the trustee was not fair. The trust game is perfectly suited to establish the investor’s level of trust (i.e., the higher the trust, the higher the transfer). Each participant played with three different types of trustees: seemingly reliable humans, seemingly unreliable humans, and the computer (i.e., a fully neutral device). By manipulating the partners’ trustworthiness, we sought to determine the extent to which OT impairs sensitivity to potential signs of dishonesty.

In one part of the game, participants were told that they would play 10 rounds with the computer, which would randomly determine the back transfers; in another part, participants were told that they would play online with real people. We gave participants a brief description of their partner before each round. Based on a pretest, these descriptions were manipulated to induce high or low trust: We combined trustworthy academic fields (e.g., philosophy) and activities (e.g., practicing first aid) to make some partners seem reliable, and untrustworthy academic fields (e.g., marketing) and activities (e.g., playing violent sports) to make other partners seem unreliable. The main effect of partner type  confirms that these descriptions were effective in inducing trust or mistrust in this study. Each participant played 10 rounds with 10 different partners (5 trustworthy, 5 untrustworthy). No back-transfers feedback was provided during the experiment, and presentation order was randomized. Before leaving the laboratory, participants were asked to guess the group (OT or control) to which they had been assigned.

Coping with stress stimulates new brain cell growth.

Interesting stuff from Lyons et al., experiments on monkeys which look like they would extrapolate to us humans:

Coping with intermittent social stress is an essential aspect of living in complex social environments. Coping tends to counteract the deleterious effects of stress and is thought to induce neuroadaptations in corticolimbic brain systems. Here we test this hypothesis in adult squirrel monkey males exposed to intermittent social separations and new pair formations. These manipulations simulate conditions that typically occur in male social associations because of competition for limited access to residency in mixed-sex groups. As evidence of coping, we previously confirmed that cortisol levels initially increase and then are restored to prestress levels within several days of each separation and new pair formation. Follow-up studies with exogenous cortisol further established that feedback regulation of the hypothalamic-pituitary-adrenal axis is not impaired. Now we report that exposure to intermittent social separations and new pair formations increased hippocampal neurogenesis in squirrel monkey males. Hippocampal neurogenesis in rodents contributes to spatial learning performance, and in monkeys we found that spatial learning was enhanced in conditions that increased hippocampal neurogenesis. Corresponding changes were discerned in the expression of genes involved in survival and integration of adult-born granule cells into hippocampal neural circuits. These findings support recent indications that stress coping stimulates hippocampal neurogenesis in adult rodents. Psychotherapies designed to promote stress coping potentially have similar effects in humans with major depression.

Solving protein folding - humans outperform computers

I remember from my graduate student days in the 1960's attending biochemistry lectures in which the professors expressed confidence that we would soon know the algorithms for predicting from the linear sequence of amino acids in a protein the three dimensional shape into which it would fold. That goal has seemed to recede from view despite increasing effort with sophisticated supercomputers. (The problem is that even a moderately sized protein can theoretically fold into more possible shapes than there are particles in the universe.) It turns out that Foldit, a multiplayer online game that engages non-scientists, is now yielding more accurate predictions of correct protein folding than one of the best known computer folding programs, Rosetta@home, which was created by molecular biologist David Baker at Univ. Washington, Seattle. (The program distributes its calculations to thousands of home computers around the world, automatically sending the results back to Baker's lab.) From the abstract of the Cooper et al. paper on their Foldit game:

...top-ranked Foldit players excel at solving challenging structure refinement problems in which substantial backbone rearrangements are necessary to achieve the burial of hydrophobic residues. Players working collaboratively develop a rich assortment of new strategies and algorithms; unlike computational approaches, they explore not only the conformational space but also the space of possible search strategies. The integration of human visual problem-solving and strategy development capabilities with traditional computational algorithms through interactive multiplayer games is a powerful new approach to solving computationally-limited scientific problems.

Two useful reviews summarize this work, one in the NYTimes, the other in Science Now.

A Brahms Capriccio as a TGIF offering...

I've been lazy about playing and recording lately, and so have decided to spend a bit more time with my piano. This Brahms Capriccio has one randomly occurring error, which happens with any piece I play regardless of how well I know the notes. (I don't do the cut and paste editing of the good parts. Whatever happens on one complete play through is what you get.) See if you can find the stumble.

Watching our brains perceive the intentions of others.

Two interesting papers on  people playing economic or cooperation games during MRI imaging that reveals activations flitting about different areas of the frontal cortex as different inferences and judgments about other game participants are made:

First, from Dolan's group, on inference of belief:

Humans have the arguably unique ability to understand the mental representations of others. For success in both competitive and cooperative interactions, however, this ability must be extended to include representations of others' belief about our intentions, their model about our belief about their intentions, and so on. We developed a "stag hunt" game in which human subjects interacted with a computerized agent using different degrees of sophistication (recursive inferences) and applied an ecologically valid computational model of dynamic belief inference. We show that rostral medial prefrontal (paracingulate) cortex, a brain region consistently identified in psychological tasks requiring mentalizing, has a specific role in encoding the uncertainty of inference about the other's strategy. In contrast, dorsolateral prefrontal cortex encodes the depth of recursion of the strategy being used, an index of executive sophistication. These findings reveal putative computational representations within prefrontal cortex regions, supporting the maintenance of cooperation in complex social decision making.

The second, from Cooper et al., on judging the intentions of others:

In social decision-making, people care both about others' outcomes and their intentions to help or harm. How the brain integrates representations of others' intentions with their outcomes, however, is unknown. In this study, participants inferred others' decisions in an economic game during functional magnetic resonance imaging. When the game was described in terms of donations, ventromedial prefrontal cortex (VMPFC) activation increased for inferring generous play and decreased for inferring selfish play. When the game was described in terms of individual savings, however, VMPFC activation did not distinguish between strategies. Distinct medial prefrontal regions also encoded consistency with situational norms. A separate network, including right temporoparietal junction and parahippocampal gyrus, was more activated for inferential errors in the donation than in the savings condition. These results demonstrate that neural responses to others' generosity or selfishness depend not only on their actions but also on their perceived intentions.

Summary highlights of Cooper et al.:
- Response to others in identical economic games depends on game description
- Liking, VMPFC distinguish generous from selfish play in “group donation” game only
- Distinct MPFC regions encode consistency with norms regardless of outcome
- Right TPJ and MTL are more activated by learning errors in donation game

My hero questioned...

In this field of studying human and animal minds, I've long been in awe of the intelligence and originality of Mark Hauser. (If you enter the name Hauser in the search box in the left column of this blog you will find no fewer than 20 previous posts on his work!)  He has published crucial experiments on morality in animals, leading him to suggest a universal moral grammar analogous to Chomsky' universal language grammar, and has also reported mirror self recognition and inferring intentions of others in monkeys. His 2002 paper with Chomsky and Fitch on language evolution is a classic.

It appears now that his ambition may have outstripped his intellect. I was saddened to read this recent article in the NYTimes saying that Hauser has gone on academic leave from Harvard after an investigation by the university found problems with his research.

... his undoing seems to have been his experiments, many of which depended on videotaping cotton-topped tamarin monkeys and noting their responses. It is easy for human observers to see the response they want and so to be fooled by the monkeys.

The papers on mirror self recognition and inferring intention are particularly in question. A psychology colleague at Columbia University noted:

First there was arbitrary interpretation of the videotapes to suit the hypothesis...The other was whether the data was real. There have been a number of papers using videotape, and all of them have to be reviewed to see if the data holds up.

Paradigm change in the practice of science?

John Markoff writes an interesting article on how fundamentally critical discourse in mathematics and physics is being transformed by the web. The case in point was the claim by a researcher that he had demonstrated that P (the set of problems that can be easily solved) does not equal NP (those problems that are difficult to solve, but easy to verify once a solution is found). This inequality is fundamental to the modern cryptography required for electronic commerce and digital privacy. The proposed proof was found to have significant shortcomings within weeks, instead of the months to years required by exchanges of written papers and debate at scientific meetings, because discussion and analysis was carried out in real time on blogs and a wiki that had been quickly set up for the purpose of collectively analyzing the paper. Clay Shirky, author of “Cognitive Surplus: Creativity and Generosity in a Connected Age” argues:

....that the emergence of these new collaborative tools is paving the way for a second scientific revolution in the same way the printing press created a demarcation between the age of alchemy and the age of chemistry...a new set of norms is emerging about what it means to do mathematics, assuming coordinated participation.

Stereotypes can prevent perceptual learning.

Some interesting observations from Rydell et al, who find that simply reminding women about the negative stereotype about women's math and visual processing performance inhibits their performance on a visual search task...

Stereotype threat (ST) refers to a situation in which a member of a group fears that her or his performance will validate an existing negative performance stereotype, causing a decrease in performance. For example, reminding women of the stereotype “women are bad at math” causes them to perform more poorly on math questions from the SAT and GRE. Performance deficits can be of several types and be produced by several mechanisms. We show that ST prevents perceptual learning, defined in our task as an increasing rate of search for a target Chinese character in a display of such characters. Displays contained two or four characters and half of these contained a target. Search rate increased across a session of training for a control group of women, but not women under ST. Speeding of search is typically explained in terms of learned “popout” (automatic attraction of attention to a target). Did women under ST learn popout but fail to express it? Following training, the women were shown two colored squares and asked to choose the one with the greater color saturation. Superimposed on the squares were task-irrelevant Chinese characters. For women not trained under ST, the presence of a trained target on one square slowed responding, indicating that training had caused the learning of an attention response to targets. Women trained under ST showed no slowing, indicating that they had not learned such an attention response.

Exercise moderates anger

Tara Parker-Pope does a summary of several studies on psychological effects of exercise, which numerous studies have shown to make people (and laboratory mice) more relaxed, confident, and happy. She describes a Univ. of Georgia study showing that students with short fuses are less likely to feel anger at a provocative stimulus after exercise.

Effect of wilderness vs. tech-world on the brain

Matt Richtel describes the efforts of a group of five neuroscientists to guage the brain effects of their multitasking high tech world by taking themselves on a 5-day rafting wilderness region of the San Juan river in the Glen Canyon preserve - no email, no cell phones, no laptops, etc.

...to understand how heavy use of digital devices and other technology changes how we think and behave, and how a retreat into nature might reverse those effects.

The group contained believers (who believe in damaging psychological effects of too much digital stimulation) and skeptics (who don't). They discussed (the following is a cut/paste/edit gemash):

...a debate that has become increasingly common as technology has redefined the notion of what is “urgent.” How soon do people need to get information and respond to it? The believers in the group say the drumbeat of incoming data has created a false sense of urgency that can affect people’s ability to focus.
...a seminal study from the University of Michigan that showed people can better learn after walking in the woods than after walking a busy street...The study indicates that learning centers in the brain become taxed when asked to process information, even during the relatively passive experience of taking in an urban setting. By extension, some scientists believe heavy multitasking fatigues the brain, draining it of the ability to focus.
...Why don’t brains adapt to the heavy stimulation, turning us into ever-stronger multitaskers?..Why wouldn’t the circuits be exercised, in a sense, and we’d get stronger?
...Behavioral studies have shown that performance suffers when people multitask... researchers are wondering whether attention and focus can take a hit when people merely anticipate the arrival of more digital stimulation...The expectation of e-mail seems to be taking up our working memory...To the extent you have less working memory, you have less space for storing and integrating ideas and therefore less to do the reasoning you need to do...Working memory is a precious resource in the brain...might they be able to prove it using imaging?
...On the trip time slows down, there are periods of silence and awed looks at surroundings...The group becomes more reflective, quieter, more focused on the surroundings...even the more skeptical of the scientists say something is happening to their brains that reinforces their scientific discussions — something that could be important to helping people cope in a world of constant electronic noise...If we can find out that people are walking around fatigued and not realizing their cognitive potential...What can we do to get us back to our full potential?

"The Law of Emotional Balance?"

I thought I would pass on to readers an example of the sort of stuff that I, retired professor and minor blog writer that I am - get sent several times a weeks to "please support or link to," presumably because internet scanning algorithms point to the MindBlog site. I got hooked into spending more time on this one than I should have because the cover email was from Stephen Takowsky, publisher of The Beverly Hills Times, who had:

...come across a book about which we are considering running an article.... Your assistance would be greatly appreciated. Our main goal at this point is to determine whether there is any established scientific evidence that tends either to support or invalidate the theory presented in the book. We want to find out if there is any scientific research that is relevant to the premise of the book.

So....   I take the bait and click on http://www.ofgrandeur.com/ , find a slightly horrific graphic and an introduction on "The Law of Emotional Balance" that raises multiple red flags.   I can't get the better of my curiosity, so I click on, find "comments from active scientist in associated field" which appear to vague clips mentioning general ideas, but which do not reference this book's specific contents.  The brief introduction/preface pretty well finally cashes it in for me, and then I find the text, whose author is one Stephen Takowsky, owner and publisher of The Beverly Hills Times ("who had come across a book..", see above....must be his evil twin). He  has solicited the opinion of hundreds or academics and reports thus far that the professors' votes are 381 nay, and 253 yea...

Still, having taken as much of my time (and yours).... I click through the book and realize that any attempt to make detailed comments would be a promethean and futile task.

Seeking immortality in words, not religion

Christopher Hitchens, atheist author of "God is Not Great: How Religion Poisons Everything," is most likely dying of esophageal cancer. Liesl Schillinger writes on how his writing of an essay on his experience of illness has

...elicited hundreds of responses from well-wishers (and some foes), who urge Mr. Hitchens in online comments (and in their prayers, many write) to accept salvation...When asked, “Do you find it insulting for people to pray for you?” Mr. Hitchens responded: “No, no. I take it kindly, under the assumption that they are praying for my recovery.”..All the same, Mr. Hitchens dismissed both the notion that his cancer would lead him to make a tardy profession of faith and the idea that, if it did, such a profession would be valid...“The entity making such a remark might be a raving, terrified person whose cancer has spread to the brain,” he said. “I can’t guarantee that such an entity wouldn’t make such a ridiculous remark, but no one recognizable as myself would ever make such a remark.”

Hitchens' friend, novelist Martin Amis,

...said his friend, like other writers, surely believed that after death, “not all of you will die,” because the printed words they leave behind constitute a kind of immortality. He added, “The desire for immortality ... explains all the extraordinary achievements, both good and bad.”

Another British-born intellectual's faith in articulacy caught the public eye this summer. On Aug. 6, Tony Judt died of amyotrophic lateral sclerosis. He had told a former student

...that he wanted his epitaph to read, “I did words.”

A custody battle for the mind - brain genes from different parents

Relatively few genes (∼100) have previously been shown to be imprinted such that their expression in progeny derives from either the maternal or paternal copy. Two papers by Gregg et al. now expand this number by an order of magnitude, and reveal complex patterns of parent-of-origin bias in gene expression in the brain that are developmentally and regionally restricted, and in many cases, sexually dimorphic. They uncovered over 1300 loci with maternal or paternal allelic bias. Comparison of the parent-of-origin allelic expression bias in the adult hypothalamus and cortex, and in the developing brain, revealed spatiotemporal and sex-specific regulation. Here are a few clips from the first and the second articles:

...Many imprinted genes are expressed in neural systems associated with feeding and motivated behaviors, and parental biases preferentially target genetic pathways governing metabolism and cell adhesion. We observed a preferential maternal contribution to gene expression in the developing brain and a major paternal contribution in the adult brain. Thus, parental expression bias emerges as a major mode of epigenetic regulation in the brain.
...Our study identified preferential selection of the maternally inherited X chromosome in glutamatergic neurons of the female cortex. Moreover, analysis of the cortex and hypothalamus identified 347 autosomal genes with sex-specific imprinting features. In the hypothalamus, sex-specific imprinted genes were mostly found in females, which suggests parental influence over the hypothalamic function of daughters. We show that interleukin-18, a gene linked to diseases with sex-specific prevalence, is subject to complex, regional, and sex-specific parental effects in the brain. Parent-of-origin effects thus provide new avenues for investigation of sexual dimorphism in brain function and disease.

I found some background given in a review of this work by Tollkuhn et. al. to be useful. Some clips:

Genomic imprinting is a phenomenon in which either the maternal or paternal copy of a gene is expressed preferentially in all progeny. This curious phenomenon, which violates classical Mendelian genetics, appears to occur only in mammals among vertebrates....An imprinted gene renders the organism functionally haploid at that locus, and permits the expression of phenotypes from mutations that would normally be recessive. In other words, imprinting precludes the protection of a back-up copy afforded by a diploid genome. It has been postulated therefore that the existence of imprinting in mammals must confer a selective advantage. What this selective pressure might be remains to be settled, but the most widely accepted explanation is that imprinting is a consequence of parental conflict over resource allocation to the progeny. Briefly, it is in the father's interest to maximize maternal resources devoted to his progeny, whereas the mother might wish to allocate resources more equitably to current and future progeny, who might conceivably result from matings with other males. This conflict is particularly acute in placental mammals, in whom the progeny develop in utero and often for prolonged gestational periods, requiring greater maternal investment. As applied to imprinting, the conflict theory predicts that paternally expressed genes should increase the use of maternal resources to produce more fit offspring. By contrast, maternally expressed genes should quell the effects of such paternally expressed genes.

Where the brain stores emotional memories

The brain mechanisms involved in forming fear memories associated with smells, sounds, and visual images are fairly well understood, but where these old fear memories are stored in the brain has not been as clear. Sacco and Sacchetti now show that these fear memories are stored in secondary, but not primary, sensory cortices - depending on whether the conditioned stimulus was visual, auditory, or olfactory. Only "old," not new, memories are stored in this way, and lesions of secondary cortices, while disrupting the old memories, do not prevent the acquisition of new memories. Here is their abstract:

Visual, acoustic, and olfactory stimuli associated with a highly charged emotional situation take on the affective qualities of that situation. Where the emotional meaning of a given sensory experience is stored is a matter of debate. We found that excitotoxic lesions of auditory, visual, or olfactory secondary sensory cortices impaired remote, but not recent, fear memories in rats. Amnesia was modality-specific and not due to an interference with sensory or emotional processes. In these sites, memory persistence was dependent on ongoing protein kinase M activity and was associated with an increased activity of layers II–IV, thus suggesting a synaptic strengthening of corticocortical connections. Lesions of the same areas left intact the memory of sensory stimuli not associated with any emotional charge. We propose that secondary sensory cortices support memory storage and retrieval of sensory stimuli that have acquired a behavioral salience with the experience.

Sex at Dawn

A recent Dan Savage column in The Onion pointed me to an interesting view of our modern sexual hangups. Ryan and Jetha in their book "Sex at Dawn" ask why monogamy and infidelity are such prominent issues in many societies. They argue that monogamy does not come naturally to our species, but rather is an imposition of the religious and cultural institutions that appeared with the advent of agriculture. These institutions, together with mainstream evolutionary psychology, maintain the conventional wisdom that men and women evolved in families where a man’s possessions and protection were exchanged for a woman’s fertility and fidelity. The authors maintain that this narrative is collapsing, and take a tour of evidence from anthropology, archeology, primatology, anatomy, and psychosexuality to offer data and arguments that our ancestors lived in egalitarian groups that shared food, child care, and often, sexual partners.

I downloaded the book for my Kindle, and found it an entertaining, spirited and engaging read, although it did have its share of inaccuracies, as well as some chaotic, repetitive and preachy sections. Their argument against the conventional evolutionary psychology view as a set of just-so stories is a common one. I would suggest that you glance at the excerpts from the book offered on their website to get an idea of bouncy tone of the prose.

The first church of robotics

Technology guru Jaron Lanier has provided a lucid NYTimes Op-Ed article on now we are misguided and damaged by thinking about increasingly intelligent machines as fellow creatures rather than tools. He sees an inappropriate new religion being expressed through engineering culture, which looses sight of the fact that technology is essentially a service. You should read the article. Here are some clips:

...the nuts and bolts of A.I. research can often be more usefully interpreted without the concept of A.I. at all. For example, I.B.M. scientists recently unveiled a “question answering” machine that is designed to play the TV quiz show “Jeopardy.” Suppose I.B.M. had dispensed with the theatrics, declared it had done Google one better and come up with a new phrase-based search engine. This framing of exactly the same technology would have gained I.B.M.’s team as much (deserved) recognition as the claim of an artificial intelligence, but would also have educated the public about how such a technology might actually be used most effectively.

On Robot Teachers:

...these robots are just a form of high-tech puppetry. The children are the ones making the transaction take place — having conversations and interacting with these machines, but essentially teaching themselves. This just shows that humans are social creatures, so if a machine is presented in a social way, people will adapt to it.

On the recommendations made by Netflix and Pandora:

...our exposure to art shouldn’t be hemmed in by an algorithm that we merely want to believe predicts our tastes accurately. These algorithms do not represent emotion or meaning, only statistics and correlations...while Silicon Valley might sell artificial intelligence to consumers, our industry certainly wouldn’t apply the same automated techniques to some of its own work. Choosing design features in a new smartphone, say, is considered too consequential a game. Engineers don’t seem quite ready to believe in their smart algorithms enough to put them up against Apple’s chief executive, Steve Jobs, or some other person with a real design sensibility.

On Simgularity University:

...The influential Silicon Valley institution preaches a story that goes like this: one day in the not-so-distant future, the Internet will suddenly coalesce into a super-intelligent A.I., infinitely smarter than any of us individually and all of us combined; it will become alive in the blink of an eye, and take over the world before humans even realize what’s happening.
...a great deal of the confusion and rancor in the world today concerns tension at the boundary between religion and modernity — whether it’s the distrust among Islamic or Christian fundamentalists of the scientific worldview, or even the discomfort that often greets progress in fields like climate change science or stem-cell research...If technologists are creating their own ultramodern religion, and it is one in which people are told to wait politely as their very souls are made obsolete, we might expect further and worsening tensions. But if technology were presented without metaphysical baggage, is it possible that modernity would not make people as uncomfortable?

Finally,

Technology is essentially a form of service. We work to make the world better. Our inventions can ease burdens, reduce poverty and suffering, and sometimes even bring new forms of beauty into the world. We can give people more options to act morally, because people with medicine, housing and agriculture can more easily afford to be kind than those who are sick, cold and starving...But civility, human improvement, these are still choices. That’s why scientists and engineers should present technology in ways that don’t confound those choices...We serve people best when we keep our religious ideas out of our work.

Similar brain cortex changes during human development and evolution

Hill et al. show that expansion of the human cortex during development involves the same brain areas that have changed the most in the evolutionary expansion from monkey to human brains.  They suggest that it is beneficial for regions of recent evolutionary expansion to remain less mature at birth, perhaps to increase the influence of postnatal experience on their development.

The cerebral cortex of the human infant at term is complexly folded in a similar fashion to adult cortex but has only one third the total surface area. By comparing 12 healthy infants born at term with 12 healthy young adults, we demonstrate that postnatal cortical expansion is strikingly nonuniform: regions of lateral temporal, parietal, and frontal cortex expand nearly twice as much as other regions in the insular and medial occipital cortex. This differential postnatal expansion may reflect regional differences in the maturity of dendritic and synaptic architecture at birth and/or in the complexity of dendritic and synaptic architecture in adults. This expression may also be associated with differential sensitivity of cortical circuits to childhood experience and insults. By comparing human and macaque monkey cerebral cortex, we infer that the pattern of human evolutionary expansion is remarkably similar to the pattern of human postnatal expansion. To account for this correspondence, we hypothesize that it is beneficial for regions of recent evolutionary expansion to remain less mature at birth, perhaps to increase the influence of postnatal experience on the development of these regions or to focus prenatal resources on regions most important for early survival.

Figure - Comparison of evolutionary and postnatal cortical surface expansion. (A) Map of regional evolutionary cortical expansion between an adult macaque and the average human adult (right hemisphere only). Evolution expansion scale indicates how many times larger the surface area is in humans relative to the corresponding area in the macaque. (B) Map of human postnatal cortical expansion for comparison. (C) Correlation map comparing postnatal to evolutionary cortical surface expansion.

We generalize negative more than positive stimuli

Schechtman et al. find that our learned response to a sound frequency associated with negative reinforcement generalizes over a broader range of adjacent frequencies (has a wider generalization curve) than the response to a positive reinforcement, both being greater than the response to a neutral stimulus. This 'better be safe than sorry' strategy makes sense in terms of survival, as noted in the author's introduction. They discuss the role of the amygdala, and suggest that individual differences in the effect that emotional valence has on generalization could underlie susceptibility to long-term effects of emotional events, possibly explaining why some people seem more susceptible to post-traumatic stress disorder (PTSD).:

If you are a dog, mistaking another dog bark for a lion roar is a shame—you might have missed a friend; but mistaking a roar for a bark can be fatal...Because a miss in this example is much more "costly" than a false-alarm, a more liberal bias for the loss-related stimulus can be expected.... in real-life, it is rarely the exact specific roar or specific bark you once heard, and stimuli rarely repeat with the exact physical properties with which they were first encountered. This means that the same logic used for immediate response should generalize to similar, yet not identical, sounds. We therefore hypothesized that valence associated with a stimulus during learning would influence the scope of generalization, and specifically, that stimuli that were previously associated with loss would generalize more than stimuli that were previously associated with gain.

Here is their abstract, followed by a graphic:

Learning includes the ability to generalize to new situations and respond to similar, yet not identical stimuli. We use stimulus generalization in humans to show that tones that were negatively reinforced induce wider generalization curves than tones that were positively reinforced, and these in turn induce wider curves than neutral memory. Importantly, these wider generalization curves persist even if outcomes for all tones are made identical, indicating that the learning induced a perceptual change, and not merely a decision bias. Moreover, it persists after taking into account loss-aversion, suggesting it is a result of valence per se, and not intensity that reflects overweighting of the aversive stimuli. This effect of emotional valence on learning suggests different locations of plasticity and network mechanisms in the brain. Particularly, it suggests that brain areas that mediate reinforcement and emotions are involved during the learning process to induce a neural representation that can support this broader behavioral generalization. In addition, these findings highlight a model for anxiety and trauma disorders in which aversive experiences affect more than they should, sometimes even in seemingly irrational situations.

Figure - The amount of generalization for negative (aversive), positive (rewarding), and no (neutral)—reinforcement... Average response rate in the generalization stage for tones in different distances from the tones that were reinforced during the acquisition stage.

Trying too hard....

Here is a nice short bit from Daniel Gilbert on how trying too hard makes us perform worse.

Are self-reflective people more depressed?

I've repeatedly heard in psychology seminars the truism that introspection (versus extroversion) correlates with depression. Grossmann and Kross, in their comparison of University of Michigan and Moscow State University students, show that this depends very much on culture. Gilbert Chin does a nice summary in the July 30 Science Magazine (picture credit: Vassilij Grivorovi Perov):

Dostoyevsky. For anyone steeped in the traditional canon of Western literature, his name elicits visions of bleak winters filled with contemplative despair. This common perception of Russian culture has fueled speculation about an underlying symbiosis between a predisposition to focus on negative feelings or experiences and a tendency toward depression. Grossmann and Kross have examined this purported linkage by contrasting self-reflective measures in Russians and Americans. Brooding correlated positively with depressive symptoms in University of Michigan students, but these were inversely related in students at Moscow State University even though the latter displayed a much greater propensity for rumination. Assessing the mode of self-reflection revealed that Russian students were more apt than Americans to examine their feelings from a third-person or observer's perspective, reconstruing the experiential details rather than recounting them from a first-person point of view. Distancing oneself in such a fashion mediated the opposite influences of American versus Russian cultures on the relation between self-reflection and negative affect.