Hygiene can hurt.

I pass on this summary from the Editor's choice section of Science, follwed by the abstract of the work mentioned. It describes further work on how failure to interact with natural environments during childhood can lead to later chronic inflammatory disorders. Also, relevant to this topic is a recent Op-Ed piece in the NYTimes called "Dirtying Up Our Diets.", and this further piece discusses our human microbiome.

As human societies urbanize, chronic inflammatory disorders become more apparent. The hygiene hypothesis suggests that individuals exposed to infection in childhood are less likely to develop inflammatory disease because exposure to microorganisms is important for stimulating responses that maintain epithelial cell integrity. Hence, in urban environments, reduced contact with the full diversity of the microbial world may be leading to the increased incidence of inflammatory disorders. Hanski et al. took a random sample of 118 adolescents from towns, villages, and isolated dwellings in eastern Finland, tested their immune function and allergic responses, surveyed their skin microflora, and investigated the biodiversity within their homes. They found several significant correlations, not least that low biodiversity was surprisingly strongly associated with atopy, and concluded that humans need to interact with natural environments for their physical health, not just for their peace of mind.

Here is the Hanski et al. abstract:

Rapidly declining biodiversity may be a contributing factor to another global megatrend—the rapidly increasing prevalence of allergies and other chronic inflammatory diseases among urban populations worldwide. According to the “biodiversity hypothesis,” reduced contact of people with natural environmental features and biodiversity may adversely affect the human commensal microbiota and its immunomodulatory capacity. Analyzing atopic sensitization (i.e., allergic disposition) in a random sample of adolescents living in a heterogeneous region of 100 × 150 km, we show that environmental biodiversity in the surroundings of the study subjects’ homes influenced the composition of the bacterial classes on their skin. Compared with healthy individuals, atopic individuals had lower environmental biodiversity in the surroundings of their homes and significantly lower generic diversity of gammaproteobacteria on their skin. The functional role of the Gram-negative gammaproteobacteria is supported by in vitro measurements of expression of IL-10, a key anti-inflammatory cytokine in immunologic tolerance, in peripheral blood mononuclear cells. In healthy, but not in atopic, individuals, IL-10 expression was positively correlated with the abundance of the gammaproteobacterial genus Acinetobacter on the skin. These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general.

Life satisfaction and economic growth.

Richard Easterlin coauthored a seminal study in 1974 that attempted to explain why the happiness score in the United Sates and elsewhere had stayed constant while per capita income had gone up. His explanation was that economic growth has a positive effect on happiness with other things being equal; however, it also raises aspirations, and aspirations have a negative effect. Aspirations are determined by society, particularly reference group income. The combination of these two effects gives rise to a Hedonic Treadmill.

He now has coauthored a study on China, an excellent setting for investigating the relationship between economic growth and life satisfaction. Over the period of economic reform, starting in 1978, income per capita rose 10-fold, China’s Human Development Index score improved impressively in all three dimensions, and through its steady, evolutionary reforms, China avoided the hardship that would have accompanied an economic revolution. Surely the Chinese people became happier as a result?

On the contrary, his latest results bear some erie similarities to the unequal effects of our current economic downturn on low versus higher income citizens:

Despite its unprecedented growth in output per capita in the last two decades, China has essentially followed the life satisfaction trajectory of the central and eastern European transition countries—a U-shaped swing and a nil or declining trend. There is no evidence of an increase in life satisfaction of the magnitude that might have been expected to result from the fourfold improvement in the level of per capita consumption that has occurred. As in the European countries, in China the trend and U-shaped pattern appear to be related to a pronounced rise in unemployment followed by a mild decline, and an accompanying dissolution of the social safety net along with growing income inequality. The burden of worsening life satisfaction in China has fallen chiefly on the lowest socioeconomic groups. An initially highly egalitarian distribution of life satisfaction has been replaced by an increasingly unequal one, with decreasing life satisfaction in persons in the bottom third of the income distribution and increasing life satisfaction in those in the top third.

Synchronized brain activity across individuals during emotional arousal.

From Nummenmaa et al.:

Sharing others’ emotional states may facilitate understanding their intentions and actions. Here we show that networks of brain areas “tick together” in participants who are viewing similar emotional events in a movie. Participants’ brain activity was measured with functional MRI while they watched movies depicting unpleasant, neutral, and pleasant emotions. After scanning, participants watched the movies again and continuously rated their experience of pleasantness–unpleasantness (i.e., valence) and of arousal–calmness. Pearson’s correlation coefficient was used to derive multisubject voxelwise similarity measures [intersubject correlations (ISCs)] of functional MRI data. Valence and arousal time series were used to predict the moment-to-moment ISCs computed using a 17-s moving average. During movie viewing, participants' brain activity was synchronized in lower- and higher-order sensory areas and in corticolimbic emotion circuits. Negative valence was associated with increased ISC in the emotion-processing network (thalamus, ventral striatum, insula) and in the default-mode network (precuneus, temporoparietal junction, medial prefrontal cortex, posterior superior temporal sulcus). High arousal was associated with increased ISC in the somatosensory cortices and visual and dorsal attention networks comprising the visual cortex, bilateral intraparietal sulci, and frontal eye fields. Seed-voxel–based correlation analysis confirmed that these sets of regions constitute dissociable, functional networks. We propose that negative valence synchronizes individuals’ brain areas supporting emotional sensations and understanding of another’s actions, whereas high arousal directs individuals’ attention to similar features of the environment. By enhancing the synchrony of brain activity across individuals, emotions may promote social interaction and facilitate interpersonal understanding.

Cumulative life stress decreases working memory and prefrontal cortex size.

Two of my colleagues here at the University of Wisconsin, Richard Davidson and Seth Pollack, have collaborated with others in a sobering study that demonstrates brain changes caused by childhood stress:

A large corpus of research indicates that exposure to stress impairs cognitive abilities, specifically executive functioning dependent on the prefrontal cortex (PFC). We collected structural MRI scans (n = 61), well-validated assessments of executive functioning, and detailed interviews assessing stress exposure in humans to examine whether cumulative life stress affected brain morphometry and one type of executive functioning, spatial working memory, during adolescence—a critical time of brain development and reorganization. Analysis of variations in brain structure revealed that cumulative life stress and spatial working memory were related to smaller volumes in the PFC, specifically prefrontal gray and white matter between the anterior cingulate and the frontal poles. Mediation analyses revealed that individual differences in prefrontal volumes accounted for the association between cumulative life stress and spatial working memory. These results suggest that structural changes in the PFC may serve as a mediating mechanism through which greater cumulative life stress engenders decrements in cognitive functioning.

A study in the same vein on rhesus monkeys also notes late life heath effects of early adversity:

This paper exploits a unique ongoing experiment to analyze the effects of early rearing conditions on physical and mental health in a sample of rhesus monkeys (Macaca mulatta). We analyze the health records of 231 monkeys that were randomly allocated at birth across three rearing conditions: mother rearing, peer rearing, and surrogate peer rearing. We show that the lack of a secure attachment relationship in the early years engendered by adverse rearing conditions has detrimental long-term effects on health that are not compensated for by a normal social environment later in life.

Finding genes that affect brain integrity and intellectual performance

Chiang et al. have looked at brain images of 472 twins and their non-twin siblings to observe gene network effects on brain microstructure and intellectual performance:

A major challenge in neuroscience is finding which genes affect brain integrity, connectivity, and intellectual function. Discovering influential genes holds vast promise for neuroscience, but typical genome-wide searches assess approximately one million genetic variants one-by-one, leading to intractable false positive rates, even with vast samples of subjects. Even more intractable is the question of which genes interact and how they work together to affect brain connectivity. Here, we report a novel approach that discovers which genes contribute to brain wiring and fiber integrity at all pairs of points in a brain scan. We studied genetic correlations between thousands of points in human brain images from 472 twins and their nontwin siblings (mean age: 23.7 ± 2.1 SD years; 193 male/279 female). We combined clustering with genome-wide scanning to find brain systems with common genetic determination. We then filtered the image in a new way to boost power to find causal genes. Using network analysis, we found a network of genes that affect brain wiring in healthy young adults. Our new strategy makes it computationally more tractable to discover genes that affect brain integrity. The gene network showed small-world and scale-free topologies, suggesting efficiency in genetic interactions and resilience to network disruption. Genetic variants at hubs of the network influence intellectual performance by modulating associations between performance intelligence quotient and the integrity of major white matter tracts, such as the callosal genu and splenium, cingulum, optic radiations, and the superior longitudinal fasciculus.

Happiness for people who can’t stand positive thinking.

Being a bit curmudgeonly about the whole Happiness industry, and having once been a contrarian guest on a west coast happiness radio program (whose message was to laugh and be positive ALL the time), I thought I should mention a nice book “The Antidote”, by Oliver Burkeman, on embracing uncertainty and rediscovering the power of negative thinking. He offers this animated trailer:

How depressives surf the web.

A brief piece with the title of this post recently appeared in the NYTimes, and is an example of annoying phenomenon: advertising by advance announcement in popular media with reference made to a "forthcoming" article. The points raised are interesting enough that the reader deserves access to what might be more thorough analysis and discussion. I'm thinking the correlations indicated might be quite spurious. For what it is worth, in a study involving the usual gaggle of undergraduate volunteers, the authors claim to have:

...identified several features of Internet usage that correlated with depression. In other words, we found a trend: in general, the more a participant’s score on the survey indicated depression, the more his or her Internet usage included these (rather technical-sounding) features — for instance, “p2p packets,” which indicate high levels of sharing files (like movies and music).

Our second major discovery was that there were patterns of Internet usage that were statistically high among participants with depressive symptoms compared with those without symptoms. That is, we found indicators: styles of Internet behavior that were signs of depressive people. For example, participants with depressive symptoms tended to engage in very high e-mail usage. This perhaps was to be expected: research by the psychologists Janet Morahan-Martin and Phyllis Schumacher has shown that frequent checking of e-mail may relate to high levels of anxiety, which itself correlates with depressive symptoms.

Another example: the Internet usage of depressive people tended to exhibit high “flow duration entropy” — which often occurs when there is frequent switching among Internet applications like e-mail, chat rooms and games. This may indicate difficulty concentrating. This finding, too, is consistent with the psychological literature: according to the National Institute of Mental Health, difficulty concentrating is also a sign of depressive symptoms among students... OTHER characteristic features of “depressive” Internet behavior included increased amounts of video watching, gaming and chatting.

Highjacked brain fallacy, and free will illusion going mainstream.

In a series of previous posts on MindBlog I have enjoyed following the continuing back and forth over free will and neuroscience,and my own sentiments are clearly revealed in my introductory web/lecture listed in the column to your left ("The I Illusion"). A raft of books on this subject has recently appeared, an example being Eagleman's "Incognito: Secret Lives of the Brain" as well as several mentioned in a recent Huffington Post essay by Victor Strenger. An interesting variation on the free will question is provided by O'Connor's discussion of a popular analogy that clouds our discussion of addiction, i.e. the portrayal of addition as a disease (not subject to our willful control, thus not the responsibility of the victim) rather than a choice.

In the “hijacked” view of addiction, the brain is the innocent victim of certain substances — alcohol, cocaine, nicotine or heroin, for example — as well as certain behaviors like eating, gambling or sexual activity...drugs like alcohol and cocaine and behaviors like gambling light up the brain’s pleasure circuitry, often bringing a burst of euphoria. Other studies indicate that people who are addicted have lower dopamine and serotonin levels in their brains, which means that it takes more of a particular substance or behavior for them to experience pleasure or to reach a certain threshold of pleasure.

However,

"A hijacker comes from outside and takes control by violent means. A hijacker takes a vehicle that is not his; hijacking is always a form of stealing and kidnapping...The analogy of addiction and hijacking involves the same category mistake as the money switched from hand to hand...It might be tempting to claim that in an addiction scenario, the drugs or behaviors are the hijackers. However, those drugs and behaviors need to be done by the person herself...In the usual cases, an individual is the one putting chemicals into her body or engaging in certain behaviors in the hopes of getting high...There is a kind of intentionality to hijacking that clearly is absent in addiction...Addiction develops over time and requires repeated and worsening use...If we think, however, of addiction as involving both choice and disease, our outlook is likely to become more nuanced.

Linking choice and responsibility is right in many ways, so long as we acknowledge that choice can be constrained in ways other than by force or overt coercion. There is no doubt that the choices of people progressing to addiction are constrained; compulsion and impulsiveness constrain choices. Many addicts will say that they choose to take that first drink or drug and that once they start they cannot stop. A classic binge drinker is a prime example; his choices are constrained with the first drink. He both has and does not have a choice. (That moment before the first drink or drug is what the philosopher Owen Flanagan describes as a “zone of control.”) But he still bears some degree of responsibility to others and to himself...Addicts are neither hijackers nor victims. It is time to retire this analogy.

Exercise bad for you?

My almost religious devotion to exercise has been slightly nudged by this piece by Gina Kolata pointing to a study by Bouchard et al., who do a rather thorough exercise study involving 1,687 people to find that

...about 10 percent actually got worse on at least one of the measures related to heart disease: blood pressure and levels of insulin, HDL cholesterol or triglycerides....But counterbalancing the 10 percent who got worse were about the same proportion who had an exaggeratedly good response on at least one measure. Others had responses ranging from little or no change up to big changes, seen in about 10 percent, where risk factor measurements improved anywhere from 20 percent to 50 percent.

The burdens of being a biped

Given my current preoccupation with my failing 70 year old knee joints, I was drawn to a brief piece by Elizabeth Pennisi with the title of this post.  Here I give a summary graphic and a few clips of her discussion:

...a number of musculoskeletal issues are traceable to our past, in particular to the switch to walking upright more than 7 million years ago…Shifting from a four-legged support system to a two-legged one put extra stress on the legs and vertebrae. Adaptations in the feet, knees, hips, pelvis, and spine accommodate these forces, but at a cost…vertebrae that break more easily, weaker bones, and feet prone to heel spurs and sprained ankles…A brief tour of the body reveals a number of design flaws, the legacy of our past…

Spine. Back pain is the leading health complaint in the United States. In dogs, horses, and even chimpanzees, the backbone is a series of vertebrae neatly stacked and evenly spaced to form a relatively stiff, gently curving beam…the human spine… is highly flexible and can even bend backward..this flexibility creates wear and tear on joint surfaces and predisposes us to osteoarthritis…One type of break, called spondylolysis, affects about 6% of the U.S. population and is a leading cause of lower-back pain in teenage athletes. In this condition, the neural arch - a triangle of bone that surrounds the spinal cord - detaches from the rest of its vertebra, allowing the spine to slip forward relative to the back of the pelvis, pinching nerves and causing pain…the problem lies in inadequate spacing between the joints connecting the vertebrae.

Feet. To cope with the added load on just two feet, the foot evolved a shock-absorbing arch by bringing what was a grasping big toe into line with the other toes. When that arch fails to form fully, as in people with flat feet, fatigue fractures can result.

Fragile bones. The added load on two feet also caused knee and hip joints to expand, creating more surface area to absorb foot-fall forces. But the joints—and vertebrae as well—evolved to be bigger by enlarging the spongy, inner bone and thinning the hard, outer bone. As a result, human bones are less dense than those of other primates. Bone...loses mass during adulthood. With humans having ever longer life spans, bones, particularly vertebrae, may become fragile and break spontaneously.

Bipedality leaves its mark in other parts of our bodies, too, for example in the difficulty of childbirth and in our vulnerability to rotator cuff injuries of the shoulder. loses mass during adulthood. With humans having ever longer life spans, bones, particularly vertebrae, may become fragile and break spontaneously.

A musical offering.

As has been my custom, I post on this blog piano video-recordings that I have recently made, this being the Chopin Nocturne in C# Minor that I played at a house concert on May 27, and subsequently recorded on June 10.

Skin Pics

One frequently comes across amazing images in cell biology. This time I felt like passing some on to readers.

The science of gaydar

Yet another study suggesting that we have an ability (if not a proficiency) to correctly judge the sexual orientation of others about 60% of the time, significantly great than chance. This piece in the New York Times points to work by Tabak and Zayas:

Research has shown that people are able to judge sexual orientation from faces with above-chance accuracy, but little is known about how these judgments are formed. Here, we investigated the importance of well-established face processing mechanisms in such judgments: featural processing (e.g., an eye) and configural processing (e.g., spatial distance between eyes). Participants judged sexual orientation from faces presented for 50 milliseconds either upright, which recruits both configural and featural processing, or upside-down, when configural processing is strongly impaired and featural processing remains relatively intact. Although participants judged women’s and men’s sexual orientation with above-chance accuracy for upright faces and for upside-down faces, accuracy for upside-down faces was significantly reduced. The reduced judgment accuracy for upside-down faces indicates that configural face processing significantly contributes to accurate snap judgments of sexual orientation.

Brain correlates of resting, alert, and meditation states.

Posner and colleagues do a nice review of neural correlates of establishing, maintaining, and switching brain states.  I thought I would pass on a few chunks from their article describing the alert state and the meditation state:

The three brain states are compared in Table 1.

The meditation state differs from the alert state induced by a warning signal in several crucial ways. First, the alert state can be induced by the simple instruction to expect a target, without requiring any practice, whereas the meditation state requires specific instruction and practice. Second, the alert state requires an external target, whereas the meditation state may not involve a target event. Third, the alert state involves primarily the neuromodulator NE, whereas dopamine (DA) has often been shown to be important to the meditation state. Finally, the alert state involves a reduction in ACC activity, likely in order to keep the mind clear to perceive and respond quickly to the target. The meditation state, however, shows increased ACC activity that serves to regulate mind wandering. As mentioned previously, Five days of integrative mind-body training (IBMT) increases brain activity in the ACC, insula, and striatum. One month of IBMT improves white matter connectivity between the ACC, striatum, and other regions. Based on these results and related work, we propose the insula, ACC, and stiatum (IAS) as key neural correlates of changing brain states (Figure 2).

Because of its role in attention and self-regulation, we hypothesize that the ACC is involved in maintaining a state by reducing conflict with other states; the insula serves a primary role in switching between states, and the striatum is linked to the reward experience and formation of habits needed to make maintenance easier. The insula and ACC work together to support the role of the autonomic nervous system in maintaining the meditation state.

Your great grandparent's experience might have altered your stress response.

This fascinating nugget from Crews et a. (open access) adds to accumulating evidence on the importance of experience induced modification of our genomes that can be passed between generations. (The experiments are on mice, because obviously you don't do this kind of study directly on humans.)

Ancestral environmental exposures have previously been shown to promote epigenetic transgenerational inheritance and influence all aspects of an individual’s life history. In addition, proximate life events such as chronic stress have documented effects on the development of physiological, neural, and behavioral phenotypes in adulthood. We used a systems biology approach to investigate in male rats the interaction of the ancestral modifications carried transgenerationally in the germ line and the proximate modifications involving chronic restraint stress during adolescence. We find that a single exposure to a common-use fungicide (vinclozolin) three generations removed alters the physiology, behavior, metabolic activity, and transcriptome in discrete brain nuclei in descendant males, causing them to respond differently to chronic restraint stress. This alteration of baseline brain development promotes a change in neural genomic activity that correlates with changes in physiology and behavior, revealing the interaction of genetics, environment, and epigenetic transgenerational inheritance in the shaping of the adult phenotype. This is an important demonstration in an animal that ancestral exposure to an environmental compound modifies how descendants of these progenitor individuals perceive and respond to a stress challenge experienced during their own life history.

MindBlog's other lives

This post is sharing with readers two aspects of Deric's private life.  I studied visual transduction over a 36 year period (1960-1996), and on Saturday May 26, near a 70th birthday in May, my former students  gathered in Madison Wisconsin (one flying from Japan for the weekend!) for a laboratory reunion.  Several former Ph.D. or postdoctoral students now head their own laboratories, are department chairs, have chair professorships, or have won academic prizes.  In preparation for the reunion, I prepared a brief web history of the laboratory, and pictures of the reunion can be found here.

On the next day, Sunday May 27,  my partner Len (on right in the picture below) and I hosted a Social/Musical at our Twin Valley home (an 1860 stone schoolhouse converted to a residence) that was attended by friends as well as many who were at the laboratory reunion.  Music selections were from the romantic literature, by Chopin, Brahms, Faure, and Debussy. Pictures of that occasion can be found here.  Included in this post is a video of the Chopin C Minor Nocture played at the Social, recorded this past Saturday. I hope to do video recordings of several of the pieces played in the next period of time.)

   

Different sorts of suspicion - brain correlates

Bhatt et al. (open access) show brain correlates of the distinction between suspicion based on a person’s general beliefs about people in the world and the situation at hand, versus suspicion that is generated by the behavior of other people:

Humans assess the credibility of information gained from others on a daily basis; this ongoing assessment is especially crucial for avoiding exploitation by others. We used a repeated, two-person bargaining game and a cognitive hierarchy model to test how subjects judge the information sent asymmetrically from one player to the other. The weight that they give to this information is the result of two distinct factors: their baseline suspicion given the situation and the suspicion generated by the other person’s behavior. We hypothesized that human brains maintain an ongoing estimate of the credibility of the other player and sought to uncover neural correlates of this process. In the game, sellers were forced to infer the value of an object based on signals sent from a prospective buyer. We found that amygdala activity correlated with baseline suspicion, whereas activations in bilateral parahippocampus correlated with trial-by-trial uncertainty induced by the buyer’s sequence of suggestions. In addition, the less credible buyers that appeared, the more sensitive parahippocampal activation was to trial-by-trial uncertainty. Although both of these neural structures have previously been implicated in trustworthiness judgments, these results suggest that they have distinct and separable roles that correspond to their theorized roles in learning and memory.

Why the liberals lost Wisconsin, and Obama may lose.

Last Tuesday the liberal bubble of Madison Wisconsin that I live in got reminded of what the rest of the state (and the U.S.) is really like:

I think this graphic from an article by Jonathan Haidt (whose book "The Righteous Mind" I'm reading, and strongly recommend you read) gives the most important part of the story. The conservative stance appeals to five of our evolved moral emotions, the liberal stance to only two.

Deep brain stimulation, fear extinction, and OCD suppression

Interesting work from Rodriguez-Romaguera et al. (open access):

Deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VC/VS) reduces symptoms of intractable obsessive-compulsive disorder (OCD), but the mechanism of action is unknown. OCD is characterized by avoidance behaviors that fail to extinguish, and DBS could act, in part, by facilitating extinction of fear. We investigated this possibility by using auditory fear conditioning in rats, for which the circuits of fear extinction are well characterized. We found that DBS of the VS (the VC/VS homolog in rats) during extinction training reduced fear expression and strengthened extinction memory. Facilitation of extinction was observed for a specific zone of dorsomedial VS, just above the anterior commissure; stimulation of more ventrolateral sites in VS impaired extinction. DBS effects could not be obtained with pharmacological inactivation of either dorsomedial VS or ventrolateral VS, suggesting an extrastriatal mechanism. Accordingly, DBS of dorsomedial VS (but not ventrolateral VS) increased expression of a plasticity marker in the prelimbic and infralimbic prefrontal cortices, the orbitofrontal cortex, the amygdala central nucleus (lateral division), and intercalated cells, areas known to learn and express extinction. Facilitation of fear extinction suggests that, in accord with clinical observations, DBS could augment the effectiveness of cognitive behavioral therapies for OCD.

Embodied metaphors and creative acts

K.-y. Leung et al. do a series of studies that suggest that embodiment of metaphors for creativity promotes creative problem solving. Given that across cultures and languages (e.g., English, Korean, Hebrew, and Chinese), metaphors associate creativity with bilateral physical orientations (thinking about a problem “on one hand” and then “on the other hand”), a first study probed divergent thinking (fluency, flexibility, and originality) by asking participants to imagine multiple uses for a university building complex while gesturing with their right hand towards a wall. During a second trial, control participants generated additional ideas while raising the same hand they had raised during the first trial; participants in the experimental condition, however, switched hands by holding their left hand toward the wall and their right hand behind their back while they generated additional ideas (participants were not aware that they would have to generate answers to the same question on both trials until the second trial began.) The experimental subjects who changed hands generated more ideas, which were also more flexible and original.

A second two part experiment looked at the "think outside of the box" metaphor by seating participants inside or outside of a 5x5 ft. box, who carried out a convergent thinking task (think of a word that is related to three cue words. For example, “measure,” “worm,” and “video” might elicit the fourth word “tape”). Participants who completed such a remote associates test while they were physically outside the box generated more correct answers. In a variation on the box theme, divergent thinking was then probed by noting the effect of having participants physically embody a box by walking in a fixed, rectangular path. Participants who could move freely were more creative in imagining identities of ambiguous objects.

Two further studies dealt with the “putting two and two together” metaphor (by noting the effect of physically moving blocks on convergent thinking), and imagining bodily motions in a virtual world similar to those of physically enacting such metaphors (as in the first and second experiments).

Here is their abstract:

Creativity is a highly sought-after skill. Prescriptive advice for inspiring creativity abounds in the form of metaphors: People are encouraged to “think outside the box,” to consider a problem “on one hand, then on the other hand,” and to “put two and two together” to achieve creative breakthroughs. These metaphors suggest a connection between concrete bodily experiences and creative cognition. Inspired by recent advances in the understanding of body-mind linkages in the research on embodied cognition, we explored whether enacting metaphors for creativity enhances creative problem solving. Our findings from five studies revealed that both physical and psychological embodiment of metaphors for creativity promoted convergent thinking and divergent thinking (i.e., fluency, flexibility, or originality) in problem solving. Going beyond prior research, which focused primarily on the kind of embodiment that primes preexisting knowledge, we provide the first evidence that embodiment can also activate cognitive processes that facilitate the generation of new ideas and connections.