The age of American unreason

A Kakutani review of Susan's Jacoby's book with the title of this post is worth a look.

Adolescent outbursts related to prefrontal and amygdala sizes

Whittle et al. have done fMRI experiments on adolescents that focused on three key brain regions which are known to represent critical nodes in neural networks supporting affective regulation: the amygdala, anterior cingulate cortex (ACC), and orbitofrontal cortex (OFC). Increased amygdala volume and a relative decrease of left versus right paralimbic ACC volumes were associated with increased duration of aggressive behaviors during parent-child interactions, with the latter association being apparent in males but not females. Decreased relative volume of left vs. right OFC was associated with greater reciprocity of dysphoric behaviors, the association also being specific to males. An absence of mean gender differences in affective behaviors suggests that the neural circuits underlying affective behaviors may differ for male and female adolescents during this age period. Here are some (slightly edited) comments by the authors:

The maturation of the prefrontal cortex and its inhibitory connections with the subcortex are key outcomes of the adolescent neurodevelopment that underlies the development of emotional and behavioral regulatory abilities. The associations of increased amygdala volume and decreased left frontal asymmetries with more negative affective behaviors may represent a delay in brain maturation. Longitudinal research would be needed to examine whether these findings have implications for the development of affective and behavioral dysregulation later in life.

The male specificity of this finding adds to a growing body of evidence that the neural mechanisms underlying affective processing differ between males and females. Males have been found to exhibit structural and functional brain asymmetries to a greater extent than females in a number of prefrontal areas, including the cingulate region. It has been suggested that these asymmetries may render males more vulnerable to certain disorders involving dysfunction of the frontal lobes such as ADHD, autism, and dyslexia. Although males in the present study did not display more aggressive behavior than females, the more pronounced relationship between ACCP asymmetry and aggressive affective behaviors in males suggests that aggressive affect in male adolescents may function as a mechanism by which their brain asymmetry is implicated in their risk for psychopathology.

Here is a useful figure that shows you the locations and variations in the anatomy of the cingulate structures being discussed:

Figure-Example of changes in the location and extent of the limbic (ACCL; highlighted in green) and paralimbic (ACCP; highlighted in blue) anterior cingulate cortices as a function of variations in the cingulate sulcus (CS; green arrow, Upper row) and paracingulate sulcus (PCS; blue arrow, Upper row). A PCS is absent in the left-hand case and present in the right-hand case. The Upper row presents parasagittal slices through an individual's T1-weighted image. The coronal section illustrates the distinction between absent (left-hand side) and present (right-hand side) cases. Notice that the ACCP is buried in the depths of the CS when the PCS is absent and extends over the paracingulate gyrus when the PCS is present. The same principle applies throughout consecutive coronal sections.

Brain imaging of our parental instinct

A group of collaborators reports in PLOS ONE a specific and rapid neural signature for our parental instinct:

Darwin originally pointed out that there is something about infants which prompts adults to respond to and care for them, in order to increase individual fitness, i.e. reproductive success, via increased survivorship of one's own offspring. Lorenz proposed that it is the specific structure of the infant face that serves to elicit these parental responses, but the biological basis for this remains elusive. Here, we investigated whether adults show specific brain responses to unfamiliar infant faces compared to adult faces, where the infant and adult faces had been carefully matched across the two groups for emotional valence and arousal, as well as size and luminosity. The faces also matched closely in terms of attractiveness. Using magnetoencephalography (MEG) in adults, we found that highly specific brain activity occurred within a seventh of a second in response to unfamiliar infant faces but not to adult faces. This activity occurred in the medial orbitofrontal cortex (mOFC), an area implicated in reward behaviour, suggesting for the first time a neural basis for this vital evolutionary process. We found a peak in activity first in mOFC and then in the right fusiform face area (FFA)....These findings provide evidence in humans of a potential brain basis for the “innate releasing mechanisms” described by Lorenz for affection and nurturing of young infants.


The group analysis reveals a significant peak in the medial orbitofrontal cortex in the 10–30 Hz band in the 0–250 ms (first two columns), 100–350 ms (third column) and 200–450 ms (fourth column) windows when participants viewed infant (upper row) and not when they viewed adult faces (lower row). The fifth column shows the integrated map over the three time windows...In order to see the extent of the spread of activity over the fusiform cortices elicited by faces, the group activity is superimposed on a ventral view of the human brain (with the cerebellum removed).

More on Brain Enhancement

Have a look at Benedict Carey's article, "Brain Enhancement Is Wrong, Right?," in the NY Times Week in Review of 3/9/08. It continues the topic of using performance enhancing drugs, following up on a Nature article that I mentioned in my Feb. 1 post on the same subject. By the way, I have been meaning to point you to Chris Chatham's excellent post on how to use caffeine properly, obtaining effects on cognitive performance equivalent to those of modifanil. Here are some clips from the Carey article:

...two Cambridge University researchers reported that about a dozen of their colleagues had admitted to regular use of prescription drugs like Adderall, a stimulant, and Provigil, which promotes wakefulness, to improve their academic performance. The former is approved to treat attention deficit disorder, the latter narcolepsy, and both are considered more effective, and more widely available, than the drugs circulating in dorms a generation ago.

Francis Fukuyama raises the broader issue of performance enhancement: “The original purpose of medicine is to heal the sick, not turn healthy people into gods.” He and others point out that increased use of such drugs could raise the standard of what is considered “normal” performance and widen the gap between those who have access to the medications and those who don’t — and even erode the relationship between struggle and the building of character.

People already use legal performance enhancers, he said, from high-octane cafe Americanos to the beta-blockers taken by musicians to ease stage fright, to antidepressants to improve mood. “So the question with all of these things is, Is this enhancement, or a matter of removing the cloud over our better selves?”.

“You can imagine a scenario in the future, when you’re applying for a job, and the employer says, ‘Sure, you’ve got the talent for this, but we require you to take Adderall.’ Now, maybe you do start to care about the ethical implications.”

Moral Neuropolitics

Gary Olson, who is Chair of the Dept. of Political Science of Maravian College in Bethlehm, PA., sent me a latest draft of his article "From Mirror Neuron to Moral Neuropolitics." It does a nice job with the literature on mirror neurons and its implications, as well as political and cultural factors that enhance and inhibit moral behaviors. Gary is willing to pass on the draft article to blog readers for further comment (web version here; PDF download here).

My main comment was that the article might - in addition to covering cultural and political factors that work against moral behaviors between groups of distant people - add more data from evolutionary and developmental biology studies that also offer some evidence for factors working against morality and compassion. There is evidence for xenophobia and aggression between groups of animals (intra-group morality and cooperation, but also inter-group aggression and warfare), well documented in Chimps (cf. Feb. 19 Killer Instincts post), and other social animals (cf. March 8 post on Hyenas). Also, experiments show that that groups of children spontaneously invent not only language, but also in-groups and out-groups (cf. July 31 post) that can become competitive.

A voice region in the monkey brain

Both human and monkey brains have visual regions that are activated most strongly by the faces of conspecifics. Our brains also have have a region that is specialized for processing human voices that is located anteriorly on the temporal lobe, on the upper bank of the superior-temporal sulcus. Logothetis and his colleagues have now found a corresponding region in monkey brains. Their abstract and a portion of one of the figures:

For vocal animals, recognizing species-specific vocalizations is important for survival and social interactions. In humans, a voice region has been identified that is sensitive to human voices and vocalizations. As this region also strongly responds to speech, it is unclear whether it is tightly associated with linguistic processing and is thus unique to humans. Using functional magnetic resonance imaging of macaque monkeys (Old World primates, Macaca mulatta) we discovered a high-level auditory region that prefers species-specific vocalizations over other vocalizations and sounds. This region not only showed sensitivity to the 'voice' of the species, but also to the vocal identify of conspecific individuals. The monkey voice region is located on the superior-temporal plane and belongs to an anterior auditory 'what' pathway. These results establish functional relationships with the human voice region and support the notion that, for different primate species, the anterior temporal regions of the brain are adapted for recognizing communication signals from conspecifics.

Figure - The color code from orange to red indicates voxels with a clear and significant preference for macaque vocalizations. The cyan-to-blue color code identifies voxels with no preference for MVocs. The slice orientation and position are shown in the lower inset

The social brains of Hyenas

There is a correlation between brain size, particularly the newer frontal lobes, and the size of the social group an animal lives in. This rule works for our primate lineage and, it turns out, also for hyenas: those with the simplest social systems have the tiniest frontal cortices. The spotted hyena, which lives in the most complex societies, has far and away the largest frontal cortex. The brown and striped hyenas, with intermediate social systems, have intermediate brains. It appears that primates are not unique in the complexity of their social lives. An article by Zimmer describes the work of Holekamp and colleagues, who have found an array of complex social behaviors in spotted hyenas that are as complex as those of baboons. The groups are comprised of 60 to 80 individuals who all know each other individually. There are alliances, rivalries, and social hierarchies headed by an alpha female. Cubs undergo an education period. Hyena clans patrol their territory borders together against neighboring clans, kills near these borders can provoke clan conflicts. These behaviors are accomplished by brains with frontal lobes that are as easily distinguished as those of social primates (see figure.)

Watching musical improvisation in the brain

Limb and Braun have done a fascinating functional MRI study of brain activity changes distinctively associated with improvisation in professional jazz pianists (compared to production of learned musical sequences). They suggest that a pattern of focal activation of the medial prefrontal (frontal polar) cortex, along with extensive deactivation of dorsolateral prefrontal and lateral orbital regions, may reflect a combination of psychological processes required for spontaneous improvisation, in which internally motivated, stimulus-independent behaviors unfold in the absence of central processes that typically mediate self-monitoring and conscious volitional control of ongoing performance.

The patterns they observe suggest cognitive dissociations that may be intrinsic to the creative process: the innovative, internally motivated production of novel material (at once rule based and highly structured) that can apparently occur outside of conscious awareness and beyond volitional control.

You can check out the experimental paradigms used and also listen to audio samples of the musical excerpts provided in supporting information.

Three-dimensional surface projection of activations and deactivations associated with improvisation during the Jazz paradigm. Medial prefrontal cortex activation, dorsolateral prefrontal cortex deactivation, and sensorimotor activation can be seen. The scale bar shows the range of t-scores; the axes demonstrate anatomic orientation. Abbreviations: a, anterior; p, posterior; d, dorsal; v, ventral; R, right; L, left.

The Advantages of Closing a Few Doors

John Tierney has a fascinating short article with the title of this post in the NY Times - noting studies that show most of us insist on keeping options open even when doing this is irrational and against our best interests. The article focuses on the work of Dan Ariely at M.I.T. and relates an interesting experiment which I suspect you will be able to relate to your own behavior:

They played a computer game that paid real cash to look for money behind three doors on the screen. (You can play it yourself, without pay, at tierneylab.blogs.nytimes.com.) After they opened a door by clicking on it, each subsequent click earned a little money, with the sum varying each time...As each player went through the 100 allotted clicks, he could switch rooms to search for higher payoffs, but each switch used up a click to open the new door. The best strategy was to quickly check out the three rooms and settle in the one with the highest rewards.

Even after students got the hang of the game by practicing it, they were flummoxed when a new visual feature was introduced. If they stayed out of any room, its door would start shrinking and eventually disappear...They should have ignored those disappearing doors, but the students couldn’t. They wasted so many clicks rushing back to reopen doors that their earnings dropped 15 percent. Even when the penalties for switching grew stiffer — besides losing a click, the players had to pay a cash fee — the students kept losing money by frantically keeping all their doors open.

Why were they so attached to those doors? The players...would probably say they were just trying to keep future options open. But that’s not the real reason, according to Dr. Ariely and his collaborator in the experiments, Jiwoong Shin, an economist who is now at Yale.

They plumbed the players’ motivations by introducing yet another twist. This time, even if a door vanished from the screen, players could make it reappear whenever they wanted. But even when they knew it would not cost anything to make the door reappear, they still kept frantically trying to prevent doors from vanishing...Apparently they did not care so much about maintaining flexibility in the future. What really motivated them was the desire to avoid the immediate pain of watching a door close.

“Closing a door on an option is experienced as a loss, and people are willing to pay a price to avoid the emotion of loss,” Dr. Ariely says. In the experiment, the price was easy to measure in lost cash. In life, the costs are less obvious — wasted time, missed opportunities. If you are afraid to drop any project at the office, you pay for it at home.

Reasoning about our irrational ways

Elizabert Kolbert writes an interesting review in The New Yorker of several books on our irrational economic and political behaviors, the field of behavioral economics. It seems very likely that as politicians and governments become more knowledgeable about the patterns and emotional mechanisms governing our blunders, they will begin to nudge people towards more rational choices. The 'opt out' plans for increasing the numbers of people with health insurance plans or retirement savings are one example of this. Obama's campaign is making very good use of some basic neuro-economics and some of his people are aware of Westin's work (see my July 11 post), as well as Lakoff's (see Jan 31 post). Hillary doesn't seem to have a clue......

A test for Alzheimer's risk

A news piece by Jennifer Couzin in the Feb. 22 Science notes that starting in about a month, for ~$400, you can send a saliva sample to Smart Genetics in Philadelphia for their "Alzheimer's Mirror" test that determines whether you have a variant of the APOE gene that indicates a risk of Alzheimer's that's 3 to 15 times higher than normal. The company plans plan to screen out those who seem emotionally unstable and provide a genetic counseling session by telephone before giving out APOE results.

Not surprisingly many physicians and researchers are expressing reservations about making this gene test widely available. What are the mental health consequences of being told you may get a disease that's neither preventable nor treatable and is invariably fatal? (It's the only genetic information that James Watson, the DNA discoverer who recently had his entire genome sequenced, kept secret.) Would it turn out that people who had this information were more likely experience depression?

An officer at Smart Genetics argues that knowing one is at higher risk might trigger practical responses, including regular memory screenings or making certain financial decisions such as buying long-term care insurance.

Chill out, and your wounds will heal faster.

It is known that anger expression can be associated with increases in cortisol secretion and lowered immune function of the sort seen with other kinds of stress. Gouin et al. at Ohio State Univ. have examined the effect of anger on wound healing by following 98 community volunteers who agreed to receive a standardized blister wound on their non-dominant forearm. They found that wounds of those who expressed little anger or displayed anger in a controlled fashion healed more rapidly than the hotheads. The hotheads exhibited higher cortisol reactivity during the blistering procedure. This enhanced cortisol secretion was in turn related to longer time to heal.

The data show more rapid wound healing in subjects with high anger control.
Measurement of the rate of transepidermal water loss (TEWL) through human skin provides a noninvasive method to monitor changes in the stratum corneum barrier function of the skin. TEWL was measured using a vapor pressure gradient estimation method. TEWL decreased as the barrier was restored; thus, monitoring of TEWL over time allowed objective evaluation of wound healing.

The Fires of Aging

Donna Holmes offers an interesting review with the title of this post, of Caleb Finch's new book "The Biology of Human Longevity." Here are a few edited clips from that review:

Metabolically speaking, we're all on fire. Current thinking in the biology of aging suggests that the normal processes cells use to burn fuel, providing energy for life, indirectly lead to much of the disease and disability that characterize aging in humans and other animals. Chemically unstable by-products of cellular oxidation--especially free oxygen radicals--can initiate the deterioration of cell membranes and macromolecules. As small "hits" causing cellular injury accumulate, the results can range from uncorrected mutations and cancers to forms of tissue damage leading to vascular pathology and Alzheimer's disease.

Oxidative damage remains a central player in the drama Fitch unfolds, but now it shares the stage with several lesser-known, equally important accomplices: inflammation, damage during development, and the hazards of overnutrition.

Finch proposes that increases in brain size and the human life span over the past million years occurred in concert with changing nutritional priorities, slower developmental rates, and a tolerance for inflammation in "dirty, invasive, and stingy" prehistoric environments. The integration of more meat into the human diet, he argues, provided protein needed for larger brains but involved new physiological and genetic trade-offs between fitness and liability for long-term damage. This scenario provides a satisfying rationale for why variants of some genes for metabolizing animal fat that are linked to a human predilection for atherosclerosis, some cancers, and the amyloid plaques characteristic of Alzheimer's disease (such as those of the ApoE gene family) are not shared by our closest primate relatives.

A primer on executive function in the prefrontal cortex

Gilbert and Burgess offer a brief review of our prefrontal brain cortex structures that enable our flexible responses to situations with alternative choices. I think it provides a good look-up reference, and so I want to excerpt a few of the summary figures and text here:

At the heart of most (but not all) theories of executive function is a distinction, or gradation, between routine (or ‘automatic’) and non-routine (or ‘controlled’) processing. Routine processing refers to mental operations that are well rehearsed or overlearned, for example reading out a word. By contrast, non-routine processing most commonly refers to mental operations that are used in situations when there is not a well-established stimulus-response association, or where a behavioural impasse has occurred (for example one notices an error, or realises that one is behaving in a sub-optimal fashion). The term ‘executive functions’ has become synonymous with those behaviours and abilities.

Determining the relative contributions of different frontal subregions to different executive functions is a highly complex matter, both theoretically and methodologically. On current evidence, however, one can make some preliminary suggestions. The figure illustrates some of the major subdivisions of the human PFC, which may be divided into lateral and medial surfaces. On the lateral surface, the PFC may be further subdivided into ventrolateral, dorsolateral, and rostral regions. Although the medial PFC is depicted as a single area in the figure, there is now strong evidence that this part of PFC can also be subdivided both on cytoarchitectonic and functional grounds. The figure shows the lateral surface split into a ventrolateral region (VLPFC), dorsolateral region (DLPFC) and rostral region (RPFC). The medial surface (MPFC) is illustrated as a single region, but recent studies indicate considerable anatomical and functional variation within this region as well. (Click to enlarge)


Ventrolateral PFC (VLPFC) is thought to be involved in comparatively simple tasks, such as short-term maintenance of information that cannot currently be perceived in ‘working memory’ (for example, memorising a phone number you have just been told, before keying the numbers into a telephone). It has also been proposed — although this is controversial — that different parts of the VLPFC are used to store different types of information (for example, the sound of a word versus its meaning). By contrast, dorsolateral PFC (DLPFC) has been most commonly implicated not so much in maintaining information that is no longer available in our environment, but in manipulating that information. For example, although DLPFC is probably not involved in processes such as remembering a telephone number, it does seem to play a role in more difficult tasks, such as dialling the number in reverse order (rearranging the digits that we have just been told). DLPFC has also been suggested to be involved in complex functions such as making plans for the future.

A brain region with strong projections to and from the DLPFC is the anterior cingulate cortex (ACC), part of the medial PFC. One influential theory proposes that this brain region detects the need for control, for example where there is competition between two or more ways of behaving in a certain situation, both of which may be triggered by events in our environment, requiring top-down input to resolve the conflict. It is suggested that the ACC does not itself provide higher-level modulation of lower-level processes, but instead signals to DLPFC when such higher-level modulation is required.

The largest, but most mysterious, sub-region of prefrontal cortex is the rostral PFC (RPFC). As a proportion of whole-brain volume, some have estimated the human RPFC to be twice as large as the corresponding region in the chimpanzee brain. Yet curiously, patients with damage restricted to the RPFC often perform well on standard neuropsychological tests, including ‘classical’ tests of executive function such as the Wisconsin card sorting test. Instead, patients with damage to this region seem to have particular difficulty in real-world ‘multitasking’ situations, such as organising a shopping trip when there are few strict constraints — participants are relatively free to organise their behaviour however they like — but there are also multiple instructions to be remembered, rules to be followed, and potential distractions in the environment. Recent accounts have focused on the role of RPFC in the most high-level human abilities, such as combining two distinct cognitive operations in order to perform a single task, trying to work out what other people are thinking (‘mentalising’), and reflecting on information we retrieve from long-term memory (‘source memory’, for example trying to work out when we last saw a person familiar to us). We recently put forward the unifying hypothesis that this brain region serves as a ‘gateway’ between cognitive processes directed towards current incoming perceptual information, versus information that we generate ourselves. We have also shown (see following figure) by a meta-analysis of functional neuroimaging results that there are distinct functions associated with different parts of the RPFC, with segregation especially between lateral versus medial regions, and between rostral versus caudal regions. (Click to enlarge)

Kahneman on happiness.

An interesting shift in opinion on what we thought we knew about measuring happiness from Nobel laureate Daniel Kahneman:

Ten years ago the generally accepted position was that there is considerable hedonic adaptation to life conditions. The effects of circumstances on life satisfaction appeared surprisingly small: the rich were only slightly more satisfied with their lives than the poor, the married were happier than the unmarried but not by much, and neither age nor moderately poor health diminished life satisfaction. Evidence that people adapt — though not completely — to becoming paraplegic or winning the lottery supported the idea of a "hedonic treadmill": we move but we remain in place. The famous "Easterlin paradox" seemed to nail it down: Self-reported life satisfaction has changed very little in prosperous countries over the last fifty years, in spite of large increases in the standard of living.

Hedonic adaptation is a troubling concept, regardless of where you stand on the political spectrum. If you believe that economic growth is the key to increased well-being, the Easterlin paradox is bad news. If you are a compassionate liberal, the finding that the sick and the poor are not very miserable takes wind from your sails. And if you hope to use a measure of well-being to guide social policy you need an index that will pick up permanent effects of good policies on the happiness of the population.

...an idea that seemed to solve these difficulties: perhaps people's satisfaction with their life is not the right measure of well-being. ..happy people have high aspirations. The aspiration treadmill offered an appealing solution to the puzzles of adaptation: it suggested that measure of life satisfaction underestimate the well-being benefits of life circumstances such as income, marital status or living in California. The hope was that measures of experienced happiness would be more sensitive.

Then after a series of experiments thoroughly refuted this hypothesis, further problems with the original issue:

...recent findings from the Gallup World Poll raise doubts about the puzzle itself. The most dramatic result is that when the entire range of human living standards is considered, the effects of income on a measure of life satisfaction (the "ladder of life") are not small at all. We had thought income effects are small because we were looking within countries. The GDP differences between countries are enormous, and highly predictive of differences in life satisfaction. In a sample of over 130,000 people from 126 countries, the correlation between the life satisfaction of individuals and the GDP of the country in which they live was over .40 – an exceptionally high value in social science. Humans everywhere, from Norway to Sierra Leone, apparently evaluate their life by a common standard of material prosperity, which changes as GDP increases. The implied conclusion, that citizens of different countries do not adapt to their level of prosperity, flies against everything we thought we knew ten years ago. We have been wrong and now we know it. I suppose this means that there is a science of well-being, even if we are not doing it very well.

Your pupils reveal shifts in your perception

Here is an interesting nugget from Christof Koch's laboratory at Cal Tech. When we look at an ambiguous image such as the Necker Cube or the duck/rabbit shown here, our perception switches back and forth between the alternatives.


It turns out that our pupil diameter increases just before the perceptual switch, and predicts its duration. Here is their abstract:

During sustained viewing of an ambiguous stimulus, an individual's perceptual experience will generally switch between the different possible alternatives rather than stay fixed on one interpretation (perceptual rivalry). Here, we measured pupil diameter while subjects viewed different ambiguous visual and auditory stimuli. For all stimuli tested, pupil diameter increased just before the reported perceptual switch and the relative amount of dilation before this switch was a significant predictor of the subsequent duration of perceptual stability. These results could not be explained by blink or eye-movement effects, the motor response or stimulus driven changes in retinal input. Because pupil dilation reflects levels of norepinephrine (NE) released from the locus coeruleus (LC), we interpret these results as suggestive that the LC–NE complex may play the same role in perceptual selection as in behavioral decision making.

Study increases learning less than testing...

Karpicke and Roediger question the common assumption that learning increases as people study and encode material, while measuring that learning by testing does not by itself produce learning. They examined undergraduates tasked with learning the meanings of 40 words in Swahili. Repeated testing of already learned words enhanced long-term recall when assessed 1 week later, whereas repeated studying had no beneficial effects. Testing required the students to retrieve the English-Swahili word associations, which suggests that encoding, although critical for the formation of a memory, may not be sufficient for its retention or consolidation. Their abstract:

Learning is often considered complete when a student can produce the correct answer to a question. In our research, students in one condition learned foreign language vocabulary words in the standard paradigm of repeated study-test trials. In three other conditions, once a student had correctly produced the vocabulary item, it was repeatedly studied but dropped from further testing, repeatedly tested but dropped from further study, or dropped from both study and test. Repeated studying after learning had no effect on delayed recall, but repeated testing produced a large positive effect. In addition, students' predictions of their performance were uncorrelated with actual performance. The results demonstrate the critical role of retrieval practice in consolidating learning and show that even university students seem unaware of this fact.

Bright light and good moods...

We are more agreeable when the light is brighter: here is the abstract, and one figure, from "Exposure to bright light is associated with positive social interaction and good mood over short time periods: A naturalistic study in mildly seasonal people" published in the Journal of Psychology:

Bright light is used to treat winter depression and might also have positive effects on mood in some healthy individuals. We examined possible links between bright light exposure and social interaction using naturalistic data. For 20 days in winter and/or summer, 48 mildly seasonal healthy individuals wore a light meter at the wrist and recorded in real-time their behaviours, mood, and perceptions of others during social interactions. Possible short-term effects of bright light were examined using the number of minutes, within any given morning, afternoon or evening, that people were exposed to light exceeding 1000 lux (average: 19.6 min). Social interactions were labelled as having occurred under conditions of no, low or high bright light exposure. Independent of season, day, time, and location, participants reported less quarrelsome behaviours, more agreeable behaviours and better mood when exposed to high but not low levels of bright light. Given that the effects were seen only when exposure levels were above average, a minimum level of bright light may be necessary for its positive effects to occur. Daily exposure levels were generally low in both winter and summer. Spending more time outdoors and improving indoor lighting may help optimize everyday social behaviour and mood across seasons in people with mild seasonality.

Figure - Quarrelsome behaviours (a) and agreeable behaviours (b) during time periods of no, low, or high levels of bright light exposure. Values are expressed as estimated least squares means of ipsatized frequencies, multiplied by a factor 100. Error bars represent standard errors of the mean. (* Significantly different from social interactions with low bright light exposure.)

Life expectancy increases

Taken from an article by Kirkwood on a systems biology approach to longevity...


The graph shows the life expectancy in the then longest-living country. During the nineteenth and early twentieth centuries, the increase was driven mainly by improvements in sanitation, housing and education, causing a steady decline in early and mid-life mortality, which was chiefly due to infections. This trend continued with the development of vaccines and then antibiotics. By the latter half of the twentieth century, there was little room for further reduction in early and mid-life mortality. The continuing increase is due almost entirely to a new phenomenon: the decline in late-life mortality.

Love speed dating

You may do better in relying on your impression after only 4 minutes of interaction with a potential partner than if you think about it a lot. Here is an engaging essay by Matt Kaplan.