MindBlog on Twitter

In spite of today's companion post on potential toxic effects of new social phenomena such as Twitter and Facebook, I can't give it a rest, and so have decided to jump in and see what happens. My twitter name is DericBownds. I've put a link to my "tweets" in the left column of the blog under the links to the podcasts. I'm thinking this might be useful not to tell you things like 'now I'm brushing my teeth', but rather to pass on ideas and URLs that I think are interesting, but that are unlikely to make it into a regular post. And to continue my (headache-inducing) entry into the Twitter/Facebook world I've linked the two. I hope I can back track and delete all this if I panic at some point.

Check out this humorous video on the follies:

Want some diet soda?

iParticipate - social participation networks

I guess I am a hard wired old curmudgeon. I wonder how many of you also get an overload headache when confronting this brave new social networking environment on the internet (Facebook, Twitter, etc)? I pass on a few points from an enthusiastic bubbly letter to Science Magazine titled "A National Initiative for Social Participation" which proposes an organized research program to study social action networks:

This program would systematically study the emerging phenomena, determine the sources of success or failure, and disseminate best practices. The payoffs are large enough to warrant an intense national effort akin to NASA's space program or the National Institutes of Health.

Some clips from the letter:

Health discussion groups have long been one of the Internet's success stories. Now, clever entrepreneurs are exploring new social participation ideas with projects such as the www.PatientsLikeMe.com Web site, where users offer their medical experiences in the hope of learning about treatment outcomes from one another. At the same time, these users are building a remarkable resource for medical research and discovery. Physicians have already discussed 30,000 cases at www.sermo.com, where they can offer insights about innovative treatments as well as detect unusual disease patterns. Large corporations also recognize the opportunities and are inviting users to store their medical histories in the Microsoft Health Vault or at Google Health.

Although social networking plays only a small role in national security, community safety could be enormously improved by expanding resident reporting systems, such as www.WatchJeffersonCounty.net, which collects reports of unusual behaviors. These reports provide important clues for civic officials to prevent crimes, control teenage gangs, or simply fix potholes.

The micro-blogging tool Twitter is now rapidly spreading, as users from Orange County fire-fighters to Mumbai police post their 140-character messages about where they are and what they are doing.

The benefits of social media participation are well understood by Obama's staff--during the campaign, they engaged 4 million donors and volunteers. To replicate their success, a National Initiative for Social Participation could stimulate effective collaborations in many professions, restore community social capital, and coordinate national service projects. The challenge is to understand what motivates participants, such as altruism, reputation, or community service. Researchers would have to develop fresh strategies that increased the conversion rates from readers to contributors from the currently typical 100 to 1 to much higher rates. Getting contributors to collaborate for ambitious efforts and to become leaders or mentors are further challenges. Coping with legitimate dangers such as privacy violations, misguided rumors, malicious vandalism, and infrastructure destruction or overload all demand careful planning and testing of potential solutions.

The huge research effort required for a National Initiative for Social Participation would tap the skills of computer scientists to build scalable and reliable systems, interface designers to accommodate diverse user needs, and social scientists to study successes and failures. The risks are substantial, but the payoffs could be enormous.

Markers of conscious access.

An interesting study from Gaillard et. al. :

What is the neural signature of the conscious perception of a visual stimulus? To address this question, we recorded neural activity directly from the brains of human subjects (who were undergoing neural surgery for medical reasons). This rare opportunity afforded greater spatial and temporal resolution than noninvasive methods used previously to probe the neural basis of consciousness. We compared neural activity concomitant with conscious and nonconscious processing of words by using a visual masking procedure that allowed us to manipulate the conscious visibility of briefly masked words. Nonconscious processing of words elicited short-lasting activity across multiple cortical areas, including parietal and visual areas. In sharp contrast, only consciously perceived words were accompanied by long-lasting effects (>200 ms) across a great variety of cortical sites, with a special involvement of the prefrontal lobes. This sustained pattern of neural activity was characterized by a specific increase of coherence between distant areas, suggesting conscious perception is broadcasted widely across the cortex.

The enlightenment returns.

I have been almost reduced to tears of gratitude by Obama's statements on restoring an American government that is guided by rationality and scientific integrity rather than a conservative religious faith that distorts both. Kurt Gottfried and Harold Varmus (see below) write an editorial in Science Magazine that salutes this (Here is the President's memorandum):

The authors of the Declaration of Independence and the Constitution of the United States were children of the Enlightenment. They understood the power that flows from combining human reason with empirical knowledge, and they assumed that the political system they were creating would thrive only in a culture that upheld the values of the Enlightenment. And thrive it did, in large part because our people and government upheld those values throughout most of U.S. history. Recently, however, the precepts of the Enlightenment were ignored and even disdained with respect to the manner in which science was used in the nation's governance. Dogma took precedence over evidence, and opinion over facts. Happily, as was made clear by two policy announcements by President Barack Obama on 9 March 2009, the break in the traditionally harmonious relationship between science and government is now ending

As the president put it, "promoting science isn't just about providing resources--it is also about protecting free and open inquiry … free from manipulation or coercion, and listening to what [scientists] tell us, even when it's inconvenient--especially when it's inconvenient." In using the words "manipulation" and "coercion," the president was not speaking purely in the abstract; he was alluding to recent breaches of a code to which government must adhere if science is to play its proper role in advising the government on such complex issues as public health, climate change, or environmental protection. When the government systematically disregards this code, it undermines the historic role of science as a bulwark of an enlightened democracy.

In the president's Memorandum on Scientific Integrity last week, addressed to the heads of all executive departments and agencies, he directed those officials to neither suppress nor alter scientific and technological findings solicited in the process of policy formulation. He also asked that scientific information developed or used by the government be made readily available to the public. To put these directives in place, the president requested the director of the Office of Science and Technology Policy to develop, within 120 days, recommendations "designed to guarantee scientific integrity throughout the executive branch" and to ensure "that scientific data is never distorted or concealed to serve a political agenda."

(Kurt Gottfried is a cofounder of the Union of Concerned Scientists and chair of its board of directors. He is professor of physics emeritus at Cornell University. Harold Varmus is president of the Memorial Sloan-Kettering Cancer Center, a cochair of the President's Council of Advisors on Science and Technology, and a former director of the National Institutes of Health.)

Brain structures that correlate with impulse control in boys.

From Boes et al.:

Emerging data on the neural mechanisms of impulse control highlight brain regions involved in emotion and decision making, including the ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC) and amygdala. Variation in the development of these regions may influence one's propensity for impulsivity and, by extension, one's vulnerability to disorders involving low impulse control (e.g. substance abuse). Here we test the hypothesis that lower impulse control is associated with structural differences in these regions, particularly on the right side, in 61 normal healthy boys aged 7–17. We assessed parent- and teacher-reported behavioral ratings of impulse control (motor impulsivity and non-planning behavior) in relation to vmPFC, ACC and amygdala volume, measured using structural magnetic resonance imaging and FreeSurfer. A regression analysis showed that the right vmPFC was a significant predictor of impulse control ratings. Follow-up tests showed (i) a significant correlation between low impulse control and decreased right vmPFC volume, especially the medial sector of the vmPFC and (ii) significantly lower right vmPFC volume in a subgroup of 20 impulsive boys relative to 20 non-impulsive boys. These results are consistent with the notion that right vmPFC provides a neuroanatomical correlate of the normal variance in impulse control observed in boys.

Future shock...

I found this video about the growth of information interesting and overwhelming...you will want to turn down the volume a bit. Again, a tip of the hat to my son Jon for finding it.

Restore damaged brain circuits with light...

I generally don't delve into cellular and molecular stuff in this blog (even though my previous lab research was at this level), but sometimes a trick comes along that is so neat that I want to mention it. Alilain et al. manage to restore breathing in rodents with acute spinal cord injury by infecting neurons that constitute the phrenic motor nucleus with a sindbis virus that expresses an algal light-gated ion channel that activates nerve cells by driving cation influx when illuminated with blue light, and also expresses green fluorescent protein (to visualize the nerve cells that have taken up the virus). The authors were able to both visualize and photostimulate the target cells that directly innervate the diaphragm muscles. Here is their abstract, following by a summary graphic from the review by Arenkiel and Peca.

Paralysis is a major consequence of spinal cord injury (SCI). After cervical SCI, respiratory deficits can result through interruption of descending presynaptic inputs to respiratory motor neurons in the spinal cord. Expression of channelrhodopsin-2 (ChR2) and photostimulation in neurons affects neuronal excitability and produces action potentials without any kind of presynaptic inputs. We hypothesized that after transducing spinal neurons in and around the phrenic motor pool to express ChR2, photostimulation would restore respiratory motor function in cervical SCI adult animals. Here we show that light activation of ChR2-expressing animals was sufficient to bring about recovery of respiratory diaphragmatic motor activity. Furthermore, robust rhythmic activity persisted long after photostimulation had ceased. This recovery was accomplished through a form of respiratory plasticity and spinal adaptation which is NMDA receptor dependent. These data suggest a novel, minimally invasive therapeutic avenue to exercise denervated circuitry and/or restore motor function after SCI.


Figure: (click to enlarge) Phrenic motor neurons in the respiratory circuit show light-induced plasticity. A: anatomical diagram of the respiratory circuit. Dashed blue and red lines represent known ipsilateral and contralateral connections between the ventral respiratory group neurons, whereas the solid gray line represents potential cross talk between the phrenic motor neurons. Lesion region is highlighted in addition to the neurons targeted for Channelrhodopsin-2 (ChR2) expression (green circles). B: cellular model of how light-gated ion influx leads to classic potentiation. Photostimulation of ChR2 drives rapid cation influx, which in turn removes N-methyl-D-aspartate receptor (NMDAR) block and allows sparse glutamate signaling to activate NMDARs. NMDAR activation might then mediate classic potentiation mechanisms by promoting AMPA receptor insertion.

Digit ratios and high frequency trading

As a followup to my Jan 16 posting on this topic, I pass on a 'letters to the editor' exchange.
From Kobe Miller:

The article by Coates et al. adds interesting evidence that a low 2D:4D ratio in men predicts success, not only in sports or music, but also in job performance. According to the authors, low-2D:4D traders perform better (i.e., they earn more) because of basic characteristics: rapid visuomotor scanning and physical reflexes. However, they overlook another frugal explanation for their findings. Recently, it has been shown that low-2D:4D men react much more strongly on performance feedback than high-2D:4D men, irrespective of the performance itself. When men with a low 2D:4D ratio find themselves in a subordinate status position (e.g., when they lose a game), they might react strongly, e.g., by acting impulsively, or perhaps even abandoning the activity if possible. Following this rationale, my hypothesis is that low-2D:4D men want to excel and therefore will look for a specific domain (in both hobbies and jobs) where they have the abilities to excel. This idea might help to explain why a low 2D:4D ratio in men is related to better performance in completely different domains such as sports and music.The same mechanism might also lead to a better performance in trading in the financial world but needs not be limited to this type of job. I expect low-2D:4D people to outperform high-2D:4D people in all kind of competitive jobs, sports, and other activities, not because of specific physical characteristics, but because of one specific psychological characteristic: a higher need for achievement.

From the original author, Coates:

Kobe Millet, in a letter commenting on the correlations we found between digit ratios and success in high-frequency trading, suggests that digit ratios gauge the psychological need to excel rather than a physiological characteristic. However, if this were true, then we would find low 2D:4D among successful people of most occupations, but I do not believe we do. One study, for example, found that faculty in the math and science departments of universities had higher more-feminine digit ratios. Furthermore, several digit-ratio studies have controlled for effort and found that relative performance in many sports is predicted by 2D:4D independently of training intensity. Lastly, our own findings show that a lower 2D:4D predicts greater trading profit and loss when the volatility of the market increases, higher volatility demanding faster reaction times. This result, together with the sporting studies mentioned above, suggests that a physiological trait rather than a psychological one is at least partly responsible for success in these fields.

We should, however, point out that our study could not fully test for the mechanism underlying the correlations between trading success and digit ratio. Only laboratory work can establish this mechanism. Our study rather was a piece of field work, a type of study we feel is sadly lacking in the new subject of neuroscience and economics. In field work, you forgo the ability to establish mechanism, but what you lose in rigor you pick up in relevance.

We are all wired differently - first analysis of a mammalian "connectome"

In a striking demonstration, Lu et al have shown that even for one of the smallest muscles in a mouse, the wiring diagram differs between two individuals, and even between the left and right sides of the same mouse. Almost every axon was longer than optimal, breaking a long-held assumption that the total wiring length in a branched axon should be minimized, since the energy costs for conduction increase with length. From Richard Robinson's review:

A complete wiring diagram—where axons go, how they branch, and where they link to muscle—has been developed for roundworms, but never before for a mammal. Performing the same feat in the mouse has presented an enormous technical challenge because of the larger size and complexity of the nervous system. The authors chose to study the interscutularis muscle, which connects the base of the ear to the middle of the skull, because it was small, accessible, and innervated by relatively few neurons...Using mice whose cells all bore a fluorescent tag, and a confocal microscope with a computer-controlled, motorized stage, the authors took thousands of individual photographs and reconstructed them to trace individual axons as they stretched across the skull, entered the muscle, branched repeatedly, and ultimately formed synapses with individual muscle fibers.

In the worm, the routes taken and connections made by axons are highly stereotyped, indicating a high degree of genetic control. But in the mouse, the actual number of axons innervating a single muscle ranged from 13 to 16, differing between mice and even between the left and right sides of the same mouse. Axonal length, including all the branches, varied much more widely, from 1.5 millimeters to 13.3 millimeters, and the number of synapses formed by a single axon ranged from a low of one (for an axon that didn't branch at all) to a high of 37. The branching pattern of axons that innervate a similar number of muscle fibers from different muscles also differed significantly, suggesting that unlike in the worm, branching in the mammal is not a deterministic process; instead it is governed by some general developmental rules, while the details of final connection are shaped by contingencies, as excess synapses are pruned.

Observing a brain rewiring itself

Our motor cortex has a topographic representation of our bodies (a homunculus), as shown in the figure. It has generally been assumed that this organization is "hard wired" by genetic instructions. Stoeckel et al. have now made the fascinating observation that in subjects with congenitally compromised hand function and compensatory skillful foot use, a representation of the foot appears in the vicinity of the normal hand area. Their results imply that during early motor development experience may play a more critical role in the shaping of genetically determined neural networks than previously assumed.

I feel what you feel if we are similar

From Serino et al.:

Social interactions are influenced by the perception of others as similar or dissimilar to the self. Such judgements could depend on physical and semantic characteristics, such as membership in an ethnic or political group. In the present study we tested whether social representations of the self and of others could affect the perception of touch. To this aim, we assessed tactile perception on the face when subjects observed a face being touched by fingers. In different conditions we manipulated the identity of the shown face. In a first experiment, Caucasian and Maghrebian (Northern African) participants viewed a face belonging either to their own or to a different ethnic group; in a second experiment, Liberal and Conservative politically active participants viewed faces of politicians belonging to their own or to the opposite political party. The results showed that viewing a touched face most strongly enhanced the perception of touch on the observer's face when the observed face belonged to his/her own ethnic or political group.

Who you are depends on how you feel.

Here is a curious bit by Ashton-James et al., from the journal Psychological Science, noting yet another distinction between Western and Asian cultures. The studies recruited students from the University of British Columbia (74 Asian and Asian Canadian students, 72 European and European Canadian students) who engaged memory tasks designed to induce positive, neutral, or negative affect. Their abstract:

We present a novel role of affect in the expression of culture. Four experiments tested whether individuals' affective states moderate the expression of culturally normative cognitions and behaviors. We consistently found that value expressions, self-construals, and behaviors were less consistent with cultural norms when individuals were experiencing positive rather than negative affect. Positive affect allowed individuals to explore novel thoughts and behaviors that departed from cultural constraints, whereas negative affect bound people to cultural norms. As a result, when Westerners experienced positive rather than negative affect, they valued self-expression less, showed a greater preference for objects that reflected conformity, viewed the self in more interdependent terms, and sat closer to other people. East Asians showed the reverse pattern for each of these measures, valuing and expressing individuality and independence more when experiencing positive than when experiencing negative affect. The results suggest that affect serves an important functional purpose of attuning individuals more or less closely to their cultural heritage.

Globalization and the internet enhance world cooperation...

Buchan et al. tabulate the relationship between a country-level globalization index (CGI) produced by the Centre for the Study of Globalization and Regionalisation at the University of Warwick, U.K and the results of a game experiment carried out 190 study participants from Columbus (Ohio, U.S.), Milan (Italy), Kazan (Tatarstan, Russia), Buenos Aires (Argentina), Johannesburg (South Africa), Tehran (Iran), and in surrounding areas. In the game (rather involved, here is a PDF describing the details), participants (who are randomly matched with 8 others from other countries and 4 local people) distribute cash tokens between 'personal', 'local', and 'world' envelopes in a sequential series of decisions that result in varying rewards depending on how many other local and other country participants give matched contributions to their local and world envelopes. Their finding and conclusion:

...as country and individual levels of globalization increase, so too does individual cooperation at the global level vis-à-vis the local level. In essence, “globalized” individuals draw broader group boundaries than others, eschewing parochial motivations in favor of cosmopolitan ones. Globalization may thus be fundamental in shaping contemporary large-scale cooperation and may be a positive force toward the provision of global public goods.

As the authors describe their nested world decision game:

A participant (Individual I) may allot the money to his or her Personal account and/or allot it to his or her Local or World group account. The 3 numbers in brackets [x, y, z] represent the returns to I (x), to another person from I's local group (y), and to a person from a different country (z) from a token allotted to I's Personal, Local, or World account, respectively. That is, a token allotted to the Personal account (dotted line) gives 1 token to I and nothing to anyone else. A token allotted to the Local account (dashed line) yields half a token to all of the 3 members of I's Local account but nothing to the people from the other two Local groups. A token allotted to I's World account (solid line) yields a quarter of a token to all of the 12 people in the World group.



Figure - Relationship between CGI and mean Allocations to World and Local Accounts. Countries are plotted according to their macrolevel globalization score on the x axis and mean aggregate levels of contribution to the World account (diamond points), and Local accounts (square points) on the y axis. The linear predictions for both variables are also plotted.

Globalization and the internet diminish cooperation.

As a partial counter to today's other MindBlog posting, a Kristoff essay, "The Daily Me," argues that we use the internet for interactions that confirm and enhance our existing attitudes, thus diminishing the prospect of cooperation or agreement with people who hold different views:

When we go online, each of us is our own editor, our own gatekeeper. We select the kind of news and opinions that we care most about....Nicholas Negroponte of M.I.T. has called this emerging news product The Daily Me. And if that’s the trend, God save us from ourselves...That’s because there’s pretty good evidence that we generally don’t truly want good information — but rather information that confirms our prejudices. We may believe intellectually in the clash of opinions, but in practice we like to embed ourselves in the reassuring womb of an echo chamber.

One of last year’s more fascinating books was Bill Bishop’s “The Big Sort: Why the Clustering of Like-Minded America is Tearing Us Apart.” He argues that Americans increasingly are segregating themselves into communities, clubs and churches where they are surrounded by people who think the way they do...The nation grows more politically segregated — and the benefit that ought to come with having a variety of opinions is lost to the righteousness that is the special entitlement of homogeneous groups...The result is polarization and intolerance.

Why jokes are hard to remember.

Natalie Angier has a nice piece on foibles of our memory in last Tuesday's science section of the NYTimes. Some edited clips:

The ease with which people forget jokes is one of those quirks...that ends up revealing a surprising amount about the underlying architecture of memory....We have our version of a buffer...a short-term working memory of limited scope and fast turnover rate...our equivalent of a save button: the hippocampus, deep in the forebrain is essential for translating short-term memories into a more permanent form...what really distinguishes the lasting from the transient is how strongly the memory is engraved in the brain...The deeper the memory, the more readily and robustly an ensemble of like-minded neurons will fire...A simple melody with a simple rhythm and repetition can be a tremendous mnemonic device...It would be a virtually impossible task for young children to memorize a sequence of 26 separate letters if you just gave it to them as a string of information, but when the alphabet is set to the tune of the ABC song with its four melodic phrases, preschoolers can learn it with ease.

Really great jokes, on the other hand, punch the lights out of do re mi. They work not by conforming to pattern recognition routines but by subverting them...Jokes work because they deal with the unexpected, starting in one direction and then veering off into another...What makes a joke successful are the same properties that can make it difficult to remember.

As frustrating as it can be to forget something new, it’s worse to forget what you already know... Behind the tying up of tongues are the too-delicate nerves of our brain’s frontal lobes and their sensitivity to anxiety and the hormones of fight or flight. The frontal lobes that rifle through stored memories and perform other higher cognitive tasks tend to shut down when the lower brain senses danger and demands that energy be shunted its way....For that reason anxiety can be a test taker’s worst foe.

Pride: Adaptive Social Emotion or Seventh Sin?

The title of this post is taken from a tidy little article by Williams and DeSteno who perform a very simple manipulation to boost the pride (self esteem) of some of the participants in an experiment (telling them they have scored brilliantly on a previous test of visuospatial acuity regardless of their actual score), finding that they then take a dominant role within a subsequent group problem-solving task (working together on a three-dimensional puzzle), and also are perceived as the most likeable interaction partners. Here is their abstract:

This experiment examined the ability of pride to serve as an adaptive emotion within the context of social interaction. After an in vivo induction of pride or a neutral state, participants engaged in a group problem-solving task. In contrast to a conventional view that pride is often associated with negative interpersonal outcomes, results confirmed that proud individuals not only took on a dominant role within the group problem-solving task, but also were perceived as the most likeable interaction partners. These findings suggest that pride, when representing an appropriate response to actual performance (as opposed to overgeneralized hubris), constitutes a functional social emotion with important implications for leadership and the building of social capital.

Musical training enhances detection of emotional components of speech.

As a followup to my Feb. 25 post, I pass on work by Kraus and collaborators at Northwestern Univ. in which they tested 30 young adults in three categories: those with no musical training, those who started learning to play a musical instrument before age 7, and those who started later but had at least 10 years of training. The scientists hooked them up to electrodes that recorded the response of the auditory brainstem to a quarter-second of an emotion-laden sound: an infant's wail (see the figure below). The subjects with the most musical experience responded the fastest to the sound. with those who had practiced since early childhood having the strongest response to the parts of the cry for which timing, pitch, and timbre were most complex. Non-musicians did not pick up on fine-grained information in the signal.
Here is their abstract, followed by a figure:

Musicians exhibit enhanced perception of emotion in speech, although the biological foundations for this advantage remain unconfirmed. In order to gain a better understanding for the influences of musical experience on neural processing of emotionally salient sounds, we recorded brainstem potentials to affective human vocal sounds. Musicians showed enhanced time-domain response magnitude to the most spectrally complex portion of the stimulus and decreased magnitude to the more periodic, less complex portion. Enhanced phase-locking to stimulus periodicity was likewise seen in musicians' responses to the complex portion. These results suggest that auditory expertise engenders both enhancement and efficiency of subcortical neural responses that are intricately connected with acoustic features important for the communication of emotional states. Our findings provide the first biological evidence for behavioral observations indicating that musical training enhances the perception of vocally expressed emotion in addition to establishing a subcortical role in the auditory processing of emotional cues.


Fig. 1. Stimulus and grand average response waveforms. Response waveforms have been shifted back in time (∼7 msec) to align the stimulus and response onsets. Boxes delineate two stimulus subsections and the corresponding brainstem responses. The first subsection (112–142 ms) corresponds to the periodic portion and the second (145–212 ms) corresponds to the more complex portion. (A) Stimulus time-amplitude waveform. (B) Stimulus spectrogram. The stimulus F₀ is superimposed as a highlighted line (∼280 Hz, left axis) with higher frequency spectral components plotted between white dotted lines (right axis). Although the F₀ is detectable during the first section, the greater acoustic complexity of the second section results in the inability of the sound analyzing software (Praat) to track the F₀. The harmonics are likewise more aperiodic. (C) The averaged responses of MusYrs and NonMus. Major peaks (β, 1 and 2) are labeled above the waveform.

A model for the outbreak of cooperation.

Helbing and Yu, in an open access article, offer a fascinating game theoretic model that turns defectors into cooperators. The trick is to incorporate success-driven migration. The graphic illustrations are interesting and clear, and I suggest you check them out. Here is their abstract:

According to Thomas Hobbes' Leviathan [1651; 2008 (Touchstone, New York), English Ed], “the life of man [is] solitary, poor, nasty, brutish, and short,” and it would need powerful social institutions to establish social order. In reality, however, social cooperation can also arise spontaneously, based on local interactions rather than centralized control. The self-organization of cooperative behavior is particularly puzzling for social dilemmas related to sharing natural resources or creating common goods. Such situations are often described by the prisoner's dilemma. Here, we report the sudden outbreak of predominant cooperation in a noisy world dominated by selfishness and defection, when individuals imitate superior strategies and show success-driven migration. In our model, individuals are unrelated, and do not inherit behavioral traits. They defect or cooperate selfishly when the opportunity arises, and they do not know how often they will interact or have interacted with someone else. Moreover, our individuals have no reputation mechanism to form friendship networks, nor do they have the option of voluntary interaction or costly punishment. Therefore, the outbreak of prevailing cooperation, when directed motion is integrated in a game-theoretical model, is remarkable, particularly when random strategy mutations and random relocations challenge the formation and survival of cooperative clusters. Our results suggest that mobility is significant for the evolution of social order, and essential for its stabilization and maintenance.

Empathy modulated by genetic background.

In mice, to be sure, but if this is like so many other genetics/behavior studies in mice, the same observations will probably soon be made in humans.

Empathy, as originally defined, refers to an emotional experience that is shared among individuals. When discomfort or alarm is detected in another, a variety of behavioral responses can follow, including greater levels of nurturing, consolation or increased vigilance towards a threat. Moreover, changes in systemic physiology often accompany the recognition of distressed states in others. Employing a mouse model of cue-conditioned fear, we asked whether exposure to conspecific distress influences how a mouse subsequently responds to environmental cues that predict this distress. We found that mice are responsive to environmental cues that predict social distress, that their heart rate changes when distress vocalizations are emitted from conspecifics, and that genetic background substantially influences the magnitude of these responses. Specifically, during a series of pre-exposure sessions, repeated experiences of object mice that were exposed to a tone-shock (CS-UCS) contingency resulted in heart rate deceleration in subjects from the gregarious C57BL/6J (B6) strain, but not in subjects from the less social BALB/cJ (BALB) strain. Following the pre-exposure sessions, subjects were individually presented with the CS-only for 5 consecutive trials followed by 5 consecutive pairings of the CS with the UCS. Pre-exposure to object distress increased the freezing responses of B6 mice, but not BALB mice, on both the CS-only and the CS-UCS trials. These physiological and behavioral responses of B6 mice to social distress parallel features of human empathy. Our paradigm thus has construct and face validity with contemporary views of empathy, and provides unequivocal evidence for a genetic contribution to the expression of empathic behavior.