Choosing whether you are anxious or chilled out - a toolkit.

This is a followup on my May 2 post, which provided a link to a lecture that I now have given (this past Tuesday) to the Chaos and Complex Systems Seminar series here at UW Madison. Responses to that talk have been very positive. I thought I would suggest that MindBlog readers who want to get quickly to the "bottom line" click straight through the presentation to the fourth part of the talk (4. What are the regulators of calm and stress to which we have conscious access?), which describes a toolkit of "bottom-up" and "top-down" approaches or techniques that can influence whether we are calm or losing it.

The topics:
1. Structures of calm and arousal: What machinery has been cobbled together over evolutionary time? 2. What is going on in our brains and bodies during calm or stress?
3. What is the nature of the self that is having this experience?
4. What are the regulators of calm and stress to which we have conscious access?

12 month old human infants recognize stable social dominance relations.

Interesting work from Mascaro and Csibra. They presented several dominance scenarios with block figures to infants, and then examined mean looking time when the dominance relation that the infant had become familiar with was subsequently violated. In the first study, for example, 9- and 12-mo-old infants were shown short animations depicting the actions of two agents. First, the “subordinate” agent was seen collecting small objects. Then the “dominant” agent entered and started to collect objects while the subordinate one let it succeed. In the second study, Twelve- and 15-mo-old infants watched familiarization events in which the agents did not collect objects but competed to stay in a little area, the boundaries of which were delimited by walls. First, the subordinate agent entered the area alone. Then the dominant agent arrived and monopolized the little area by repeatedly pushing the subordinate agent away. In subsequent viewings these dominance relations were either confirmed or violated. Mean gaze time increased significantly when the familiarized sequence was violated. Here is their abstract:

What are the origins of humans’ capacity to represent social relations? We approached this question by studying human infants’ understanding of social dominance as a stable relation. We presented infants with interactions between animated agents in conflict situations. Studies 1 and 2 targeted expectations of stability of social dominance. They revealed that 15-mo-olds (and, to a lesser extent, 12-mo-olds) expect an asymmetric relationship between two agents to remain stable from one conflict to another. To do so, infants need to infer that one of the agents (the dominant) will consistently prevail when her goals conflict with those of the other (the subordinate). Study 3 and 4 targeted the format of infants’ representation of social dominance. In these studies, we found that 12- and 15-mo-olds did not extend their expectations of dominance to unobserved relationships, even when they could have been established by transitive inference. These results suggest that infants' expectation of stability originates from their representation of social dominance as a relationship between two agents rather than as an individual property. Infants’ demonstrated understanding of social dominance reflects the cognitive underpinning of humans’ capacity to represent social relations, which may be evolutionarily ancient, and may be shared with nonhuman species.

In study 1,

Further work on when two heads are better or worse than one.

Studies that compare the accuracy of individual and group decision yield somewhat inconsistent results. The key to benefiting from other minds is to know when to rely on the group and when to walk alone. To follow up a thread started in two previous posts (here and here) on when two heads are better or worse than one, I pass on this work by Koriat. He shows that in an inference task involving two alternatives, optimal results are obtained with the simple heuristic of selecting the response expressed with the higher—or in the case of more than two heads, highest—degree of confidence. Here is the abstract:

A recent study, using a perceptual task, indicated that two heads were better than one provided that the members could communicate freely, presumably sharing their confidence in their judgments. Capitalizing on recent work on subjective confidence, I replicated this effect in the absence of any dyadic interaction by selecting on each trial the decision of the more confident member of a virtual dyad. However, because subjective confidence monitors the consensuality rather than the accuracy of a decision, when most participants were in error, reliance on the more confident member yielded worse decisions than those of the better individual. Assuming that for each issue group decisions are dominated by the more confident member, these results help specify when groups will be more or less accurate than individuals.

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Brain correlates of whether we help someone suffering.

I thought I would pass on this interesting paper that is being discussed by an emotion seminar group here on the Univ. of Wisc. campus.  Hein et al. touch on the question of whether we are fundamentally good or bad. Is our human nature always fundamentally prosocial?   They find it depends very much on whether we are helping one of "us" or one of "them."  Their summary of the main points, followed by their abstract:

• Empathy-related brain responses in anterior insula predict costly helping
• Helping ingroup and outgroup members is predicted by distinct neural responses
• Brain responses predict behavior toward outgroup members better than self-reports

Little is known about the neurobiological mechanisms underlying prosocial decisions and how they are modulated by social factors such as perceived group membership. The present study investigates the neural processes preceding the willingness to engage in costly helping toward ingroup and outgroup members. Soccer fans witnessed a fan of their favorite team (ingroup member) or of a rival team (outgroup member) experience pain. They were subsequently able to choose to help the other by enduring physical pain themselves to reduce the other's pain. Helping the ingroup member was best predicted by anterior insula activation when seeing him suffer and by associated self-reports of empathic concern. In contrast, not helping the outgroup member was best predicted by nucleus accumbens activation and the degree of negative evaluation of the other. We conclude that empathy-related insula activation can motivate costly helping, whereas an antagonistic signal in nucleus accumbens reduces the propensity to help.

Metaphors are the tip of the mind's iceberg.

An essay by Benjamin Bergen does a nice summary of the importance of ideas in Lakoff and Johnson's 1980 book, "Metaphors We Live By."  (I remember being completely awed and fascinated by this book when it appeared.) They established the point that metaphor is not linguistic window-dressing, it reveals fundamental operations of mind.

...Lakoff and Johnson observed that real metaphorical language as actually used isn't haphazard at all. Instead, it's systematic and coherent...Metaphor is unidirectional, from concrete to abstract.(You can't reverse metaphors. While you can say "He's clean" to mean he has no criminal record, you can't say "He's moral" to mean that he bathed recently.)

Metaphorical expressions are coherent with one another. Take the example of understanding and seeing. ...You always describe the understander as the seer, the understood idea as the seen object, the act of understanding as seeing, the understandability of the idea as the visibility of the object, and so on. In other words, the aspects of seeing you use to talk about aspects of understanding stand in a fixed mapping to one another.

These observations led Lakoff and Johnson to propose that there was something going on with metaphor that was deeper than just the words. They argued that the metaphorical expressions in language are really only surface phenomena, organized and generated by mappings in people's minds. For them, the reason metaphorical language exists and the reason why it's systematic and coherent is that people think metaphorically. You don't just talk about understanding as seeing; you think about understanding as seeing. You don't just talk about morality as cleanliness; you think about morality as cleanliness. And it's because you think metaphorically—because you systematically map certain concepts onto others in your mind—that you talk metaphorically. The metaphorical expressions are merely the visible tip of the iceberg.

As explanations go, this one covers all the bases. It's elegant in that it explains messy and complicated phenomena (the various metaphorical expressions we have that describe understanding as seeing, for instance) in terms of something much simpler—a structured mapping between the two conceptual domains in people's minds. It's powerful in that it explains things other than metaphorical language—recent work in cognitive psychology shows that people think metaphorically even in the absence of metaphorical language; affection as warmth, morality as cleanliness. As a result, the conceptual metaphor explanation helps to explain how it is that we understand abstract concepts like affection or morality at all—by metaphorically mapping them onto more concrete ones.

...the conceptual metaphor explanation is transformative—it flies in the face of the accepted idea that metaphor is just a linguistic device based on similarity. In an instant, it made us rethink 2000 years of received wisdom.

Homophobic? Maybe you're gay!

Two of the co-authors of an interesting article on homophobia in the Journal of Personality and Social Psychology summarize their work in a New York Times piece. They ask why political and religious figures who campaign against gay rights are so often implicated in sexual encounters with same-sex partners. Their:

... paper describes six studies conducted in the United States and Germany involving 784 university students. Participants rated their sexual orientation on a 10-point scale, ranging from gay to straight. Then they took a computer-administered test designed to measure their implicit sexual orientation. In the test, the participants were shown images and words indicative of hetero- and homosexuality (pictures of same-sex and straight couples, words like “homosexual” and “gay”) and were asked to sort them into the appropriate category, gay or straight, as quickly as possible. The computer measured their reaction times.

The twist was that before each word and image appeared, the word “me” or “other” was flashed on the screen for 35 milliseconds — long enough for participants to subliminally process the word but short enough that they could not consciously see it. The theory here, known as semantic association, is that when “me” precedes words or images that reflect your sexual orientation (for example, heterosexual images for a straight person), you will sort these images into the correct category faster than when “me” precedes words or images that are incongruent with your sexual orientation (for example, homosexual images for a straight person). This technique, adapted from similar tests used to assess attitudes like subconscious racial bias, reliably distinguishes between self-identified straight individuals and those who self-identify as lesbian, gay or bisexual. 

Over 20 percent of the participants who identified themselves as highly straight indicated some level of same-sex attraction (i.e., associated “me” most rapidly with gay-related words and pictures). These individuals were more likely than others to favor anti-gay policies, impose harsher penalties on petty crimes perpetrated by those thought to be gay, and were raised by parents perceived to be controlling, less accepting, and more prejudiced against homosexuals.

Structures of arousal and calm - This year's MindBlog Web Lecture

Having posted lectures that I have given for the past two years,  I thought I would pass on this year's talk. The topic of the talk derives from a scan of the  thousands of posts I have done since 2006 on Deric’s MindBlog. The scan for my favorites yielded groupings into areas that have I been most interested in, and suggested possible topics for a talk.  Some examples:

-Freud redux - The constancy of models of mind
-Can we cope with understanding out minds?
-Biology designs us for faith
-The 200 millisecond manager - it's all over in less   than a second.
-Are you breathing? - The evolution of arousal and calm
-What woke up this morning? And what can you do about it?
-The necessity of self delusion.

I decided to go with:

“Are you holding your breath?”  -  Structures of arousal and calm

You can find this talk via the MINDBLOG WEB LECTURES list in the column to your left, or HERE.

These take you to a Web techie toy (new to me) called Prezi, an idea and presentation manager.  Click on "More" in the bottom right corner of the window, go to full screen, and proceed through the presentation by clicking on the arrow at the bottom right of the screen. If you move the cursor to the left margin, zoom buttoms appear. Clicking on an area of the screen allows lets you move about on your own. Clicking on one of the URL links in the text opens that link in a new tab on your browser.  Press escape to look at that reference, then go back to the talk tab and resume the talk sequence.

From the first graphic in the presentation:

This is the web version of a talk given on Tuesday May 8, 2012, to the Tuesday noon Chaos and Complex Systems Seminar at the University of Wisconsin, Madison. It discusses some of the structures of calm and arousal - whether we are chilled out or losing it.   The material is cooked down to four sections that: (1), note some structures regulating calm and arousal  (2), list some brain and body correlates (3) consider the definition of the self that stresses or calms.  (4) discuss bottom-up and top-down regulators under some voluntary control that can alter the balance between calm and arousal. 

Analytic thinking promotes religious disbelief.

From Gervais and Norenzayan's introduction to their paper:

According to dual-process theories of human thinking, there are two distinct but interacting systems for information processing. One (System 1) relies upon frugal heuristics yielding intuitive responses, while the other (System 2) relies upon deliberative analytic processing. Although both systems can at times run in parallel, System 2 often overrides the input of system 1 when analytic tendencies are activated and cognitive resources are available. Dual-process theories have been successfully applied to diverse domains and phenomena across a wide range of fields

If religious belief emerges through a converging set of intuitive processes, and analytic processing can inhibit or override intuitive processing, then analytic thinking may undermine intuitive support for religious belief. Thus, a dual-process account predicts that analytic thinking may be one source of religious disbelief. Recent evidence is consistent with this hypothesis.

We adopted three complementary strategies to test for robustness and generality. First, study 1 tested whether individual differences in the tendency to engage analytic thinking are associated with reduced religious belief. Second, studies 2 to 5 established causation by testing whether various experimental manipulations of analytic processing, induced subtly and implicitly, encourage religious disbelief. These manipulations of analytic processing included visual priming, implicit priming, and cognitive disfluency. Third, across studies, we assessed religious belief using diverse measures that focused primarily on belief in and commitment to religiously endorsed supernatural agents. Samples consisted of participants from diverse cultural and religious backgrounds

From their abstract:

...Combined, these studies indicate that analytic processing is one factor (presumably among several) that promotes religious disbelief. Although these findings do not speak directly to conversations about the inherent rationality, value, or truth of religious beliefs, they illuminate one cognitive factor that may influence such discussions.

We don't project our visceral states onto dissimilar others.

Interesting observations from O’Brien and Ellsworth on limits to the empathy of our embodied cognition:

What people feel shapes their perceptions of others. We have examined the assimilative influence of visceral states on social judgment. Replicating prior research, we found in a first experiment that participants who were outside during winter overestimated the extent to which other people were bothered by cold, and in a second study found that participants who ate salty snacks without water thought other people were overly bothered by thirst. However, in both studies, this effect evaporated when participants believed that the other people under consideration held political views opposing their own. Participants who judged these dissimilar others were unaffected by their own strong visceral-drive states, a finding that highlights the power of dissimilarity in social judgment. Dissimilarity may thus represent a boundary condition for embodied cognition and inhibit an empathic understanding of shared out-group pain. Our findings reveal the need for a better understanding of how people’s internal experiences influence their perceptions of the feelings and experiences of those who may hold values different from their own.

Facial theory of politics

I wanted to pass on this piece by Leonard Mlodinow to continue the thread started in previous posts (also, click on 'faces' in the blog categories in the left column).  He points to work suggesting that voters, regardless of issues and ideology, unconsciously favor the candidate that seems to radiate competence and most 'looks the part.'

Better brains through exercise

Reynolds points to some fascinating work by Justin Rhodes that upends previous assumptions about the importance of a rich environment leading to increased brain power (in mice). Apparently physical exercise alone is the sine qua non. Rhodes:

...gathered four groups of mice and set them into four distinct living arrangements. One group lived in a world of sensual and gustatory plenty, dining on nuts, fruits and cheeses, their food occasionally dusted with cinnamon, all of it washed down with variously flavored waters. Their “beds” were colorful plastic igloos occupying one corner of the cage. Neon-hued balls, plastic tunnels, nibble-able blocks, mirrors and seesaws filled other parts of the cage. Group 2 had access to all of these pleasures, plus they had small disc-shaped running wheels in their cages. A third group’s cages held no embellishments, and they received standard, dull kibble. And the fourth group’s homes contained the running wheels but no other toys or treats. All the animals completed a series of cognitive tests at the start of the study and were injected with a substance that allows scientists to track changes in their brain structures. Then they ran, played or, if their environment was unenriched, lolled about in their cages for several months. Afterward, Rhodes’s team put the mice through the same cognitive tests and examined brain tissues. It turned out that the toys and tastes, no matter how stimulating, had not improved the animals’ brains...Animals that didn’t run, no matter how enriched their world was otherwise, did not improve their brainpower in complex, lasting ways...

Both human and animal studies have shown that exercise increases levels of brain-derived neurotropic factor, or B.D.N.F., that stimulates growth of the hippocampus as well as some other brain areas, and also improves performance on cognitive tests.

We're talking mice, not humans, and studies on human children and adults continue to suggest that mental exercises like the n-back test to enhance working memory that I've mentioned in several posts can increase fluid intelligence in a long term, but still reversible, way (use it or loose it.)

Walking on air.

I thought I would pass on this nifty video. Calming, but at the same time sobering to see how people are down there.

Physical exertion can impair recall and recognition.

Some interesting observations from Hope et al.:

Understanding memory performance under different operational conditions is critical in many occupational settings. To examine the effect of physical exertion on memory for a witnessed event, we placed two groups of law-enforcement officers in a live, occupationally relevant scenario. One group had previously completed a high-intensity physical-assault exercise, and the other had not. Participants who completed the assault exercise showed impaired recall and recognition performance compared with the control group. Specifically, they provided significantly less accurate information concerning critical and incidental target individuals encountered during the scenario, recalled less briefing information, and provided fewer briefing updates than control participants did. Exertion was also associated with reduced accuracy in identifying the critical target from a lineup. These results support arousal-based competition accounts proposing differential allocation of resources under physiological arousal. These novel findings relating to eyewitness memory performance have important implications for victims, ordinary citizens who become witnesses, and witnesses in policing, military, and related operational contexts.

Increases in stress and amygdala volume reversed by mindfulness meditation.

Davidson and McEwen offer a nice review of stress induced changes in the amygdala and hippocampus, and also describe experiments showing that mindfulness meditation can decrease both stress behavior and amygdala size. Here is their abstract, followed by two figures from the paper:

Experiential factors shape the neural circuits underlying social and emotional behavior from the prenatal period to the end of life. These factors include both incidental influences, such as early adversity, and intentional influences that can be produced in humans through specific interventions designed to promote prosocial behavior and well-being. Here we review important extant evidence in animal models and humans. Although the precise mechanisms of plasticity are still not fully understood, moderate to severe stress appears to increase the growth of several sectors of the amygdala, whereas the effects in the hippocampus and prefrontal cortex tend to be opposite. Structural and functional changes in the brain have been observed with cognitive therapy and certain forms of meditation and lead to the suggestion that well-being and other prosocial characteristics might be enhanced through training.

Figure - Chronic stress causes neurons to shrink or grow, but not necessarily to die. Representation of the chronic stress effects detected in animal models on growth or retraction of dendrites in the basolateral amygdala and orbitofrontal cortex (growth) and in the CA3 hippocampus, dentate gyrus and medial prefrontal cortex (shrinkage). These effects are largely reversible in young adult animals, although aging appears to compromise resilience and medial prefrontal cortex recovery.

Figure - Change in gray matter volume in the right basolateral amygdala from pre to post 8 weeks of mindfulness based stress reduction was associated with decreases in perceived stress over this same time period (see Hölzel et al.). Individuals undergoing MBSR who showed the largest decreases in perceived stress also showed the largest decreases in basolateral amygdala gray matter volume.

Both mental and physical effort rise from deep sub-cortical structures.

Schmidt et al. show that a common motivational system within the basala ganglia underlies performance of both mental and physical efforts.

Mental and physical efforts, such as paying attention and lifting weights, have been shown to involve different brain systems. These cognitive and motor systems, respectively, include cortical networks (prefronto-parietal and precentral regions) as well as subregions of the dorsal basal ganglia (caudate and putamen). Both systems appeared sensitive to incentive motivation: their activity increases when we work for higher rewards. Another brain system, including the ventral prefrontal cortex and the ventral basal ganglia, has been implicated in encoding expected rewards. How this motivational system drives the cognitive and motor systems remains poorly understood. More specifically, it is unclear whether cognitive and motor systems can be driven by a common motivational center or if they are driven by distinct, dedicated motivational modules. To address this issue, we used functional MRI to scan healthy participants while performing a task in which incentive motivation, cognitive, and motor demands were varied independently. We reasoned that a common motivational node should (1) represent the reward expected from effort exertion, (2) correlate with the performance attained, and (3) switch effective connectivity between cognitive and motor regions depending on task demand.

The ventral striatum fulfilled all three criteria and therefore qualified as a common motivational node capable of driving both cognitive and motor regions of the dorsal striatum. Thus, we suggest that the interaction between a common motivational system and the different task-specific systems underpinning behavioral performance might occur within the basal ganglia.

Liljeholm and O'Doherty also offer context and perspective on this work.

Young blood enhances repair of old brains.

In a Neuroscience perspective in Science Redmond and Chan summarize work of Ruckh et al. showing that factors present in the blood of younger mice (introduced by joining the circulatory systems of a young and old mouse) enhance repair of the myelin sheath around neuronal axons in the older mice. Here is a graphic from the summary:

Legend - The circulatory system of an “old” mouse (gray) with a demyelinated lesion was surgically joined with that of a healthy “young” mouse (white. The old mouse exhibited enhanced remyelination relative to the control, an old-old mouse pair. Remyelination depended on the recruitment of circulatory factors from the young mouse, including macrophages. Resident “old” oligodendroglia retain remyelination potential even as they age, but macrophage-mediated clearance of inhibitory myelin debris from the lesion may become impaired.

John Cleese on creativity

For the second time, I've come across some engaging comments by the British actor John Cleese, and I though I would pass them on. Cleese's model for creativity centers on the interplay of two modes of operating – open, where we take a wide-angle, abstract view of the problem and allow the mind to ponder possible solutions, and closed, where we zoom in on implementing a specific solution with narrow precision.  In the 10 minute video, he stresses the role of the unconscious. 

-Space ("You can't become playful, and therefore creative, if you're under your usual pressures.")

-Time ("It's not enough to create space; you have to create your space for a specific period of time.")


-Time ("Giving your mind as long as possible to come up with something original," and learning to tolerate the discomfort of pondering time and indecision.)

-Confidence ("Nothing will stop you being creative so effectively as the fear of making a mistake.")
 -Humor ("The main evolutionary significance of humor is that it gets us from the closed mode to the open mode quicker than anything else.")

Further points:

Creativity is not a talent. It is a way of operating.

We need to be in the open mode when pondering a problem – but! – once we come up with a solution, we must then switch to the closed mode to implement it. Because once we've made a decision, we are efficient only if we go through with it decisively, undistracted by doubts about its correctness.

To be at our most efficient, we need to be able to switch backwards and forward between the two modes. But – here's the problem – we too often get stuck in the closed mode. Under the pressures which are all too familiar to us, we tend to maintain tunnel vision at times when we really need to step back and contemplate the wider view. This is particularly true, for example, of politicians. The main complaint about them from their nonpolitical colleagues is that they've become so addicted to the adrenaline that they get from reacting to events on an hour-by-hour basis that they almost completely lose the desire or the ability to ponder problems in the open mode. Cleese concludes with a beautiful articulation of the premise and promise of his recipe for creativity:

This is the extraordinary thing about creativity: If just you keep your mind resting against the subject in a friendly but persistent way, sooner or later you will get a reward from your unconscious.

Swarm Intelligence - The Simpleton Ant and the Intelligent Ants

Another posting from my scan of responses to the edge.org annual question "What is your favorite deep elegant or beautiful explanation?" In his essay, Robert Sapolsky does a curious stroll through several candidate beautiful stories he considered (the double helix, the work of Hubel and Wiesel on how the visual brain extracts features, how the GI tract moves stuff along…) and comes to rest on this selection:

...emergence and complexity, as represented by "swarm intelligence."

Observe a single ant, and it doesn't make much sense, walking in one direction, suddenly careening in another for no obvious reason, doubling back on itself. Thoroughly unpredictable.

The same happens with two ants, a handful of ants. But a colony of ants makes fantastic sense. Specialized jobs, efficient means of exploiting new food sources, complex underground nests with temperature regulated within a few degrees. And critically, there's no blueprint or central source of command—each individual ants has algorithms for their behaviors. But this is not wisdom of the crowd, where a bunch of reasonably informed individuals outperform a single expert. The ants aren't reasonably informed about the big picture. Instead, the behavior algorithms of each ant consist of a few simple rules for interacting with the local environment and local ants. And out of this emerges a highly efficient colony.

Ant colonies excel at generating trails that connect locations in the shortest possible way, accomplished with simple rules about when to lay down a pheromone trail and what to do when encountering someone else's trail—approximations of optimal solutions to the Traveling Salesman problem. This has useful applications. In "ant-based routing," simulations using virtual ants with similar rules can generate optimal ways of connecting the nodes in a network, something of great interest to telecommunications companies. It applies to the developing brain, which must wire up vast numbers of neurons with vaster numbers of connections without constructing millions of miles of connecting axons. And migrating fetal neurons generate an efficient solution with a different version of ant-based routine.

A wonderful example is how local rules about attraction and repulsion (i.e., positive and negative charges) allow simple molecules in an organic soup to occasionally form more complex ones. Life may have originated this way without the requirement of bolts of lightening to catalyze the formation of complex molecules

. And why is self-organization so beautiful to my atheistic self? Because if complex, adaptive systems don't require a blue print, they don't require a blue print maker. If they don't require lightening bolts, they don't require Someone hurtling lightening bolts. 

Two different ways of making choices in two brain areas.

Kolling et al. note brain correlates of two different ways of making decisions. They use fMRI of humans to examine neural correlates of foraging, which involves a choice of whether or not to engage with options as they are encountered (which is different from the sort of binary choice between currently available options studied by behavioral economics.) Here is their abstract:

Behavioral economic studies involving limited numbers of choices have provided key insights into neural decision-making mechanisms. By contrast, animals’ foraging choices arise in the context of sequences of encounters with prey or food. On each encounter, the animal chooses whether to engage or, if the environment is sufficiently rich, to search elsewhere. The cost of foraging is also critical. We demonstrate that humans can alternate between two modes of choice, comparative decision-making and foraging, depending on distinct neural mechanisms in ventromedial prefrontal cortex (vmPFC) and anterior cingulate cortex (ACC) using distinct reference frames; in ACC, choice variables are represented in invariant reference to foraging or searching for alternatives. Whereas vmPFC encodes values of specific well-defined options, ACC encodes the average value of the foraging environment and cost of foraging.

More on why exercise is so good for us...

Many studies show that egular physical activity confers enormous fitness benefits. Exercise training enhances muscular endurance and strength, expends calories, and combats the development of common diseases such as obesity and type 2 diabetes. The effects of exercise are systemic and seemingly cannot be explained solely by the expenditure of calories in muscle.  Daniel Kelly writes a perspective on recent work showing how a new protein messenger named irisin (after Iris, the Greek messenger goddess) is released during muscle activity and triggers remodeling and energy expenditure in distant subcutaneous fat tissue deposits. Here is a summary figure of the muscle cell (myocyte) - fat cell (adipocyte) connection. 

Figure: The proposed irisin messenger system is depicted for humans [but was characterized in mice]. Exercise and energy expenditure induces the transcriptional regulator PGC-1α in the skeletal myocyte, which in turn drives the production of the membrane protein FNDC5. The circulating factor irisin, cleaved from FNDC5, activates thermogenic programs in white adipose tissue (“browning”), including mitochondrial biogenesis and the expression of uncoupling protein 1 (UCP1), leading to mitochondrial heat production and energy expenditure.