Posts Tagged ‘social behavior’

By Lucy Huang

Ants infected with fungal pathogens steer clear of other cliques within the colony—avoiding wider infection, and allowing for a sort of immunity. Lucy Huang reports.

It’s peak cold and flu season, which means taking a lot of preventive measures. Frequent hand-washing is a must. As is avoiding co-workers or friends who are sick. But we humans are not the only animals that change behavior to keep diseases at bay. So do ants.

“So there are the foragers and the nurses– it’s two different groups of work.”

Nathalie Stroeymeyt of the University of Lausanne. She and colleagues observed ants to see their reaction to the presence of a pathogen.

“With the nurses staying inside the nurse taking care of the brood and being made of young workers. And the foragers are all the workers at outside of the nest to collect food and defend the territory.”

Forager ants are at greater risk of getting exposed to diseases because they leave the safety of the nest. So the researchers sprayed a common fungus on a small group of forager ants and then followed their movements to see the way other ants reacted.

“We marked all ants in the colony was individual labels, which carries these two-dimensional bar code marks like QR code which is automatically detected and recorded using a tracking system.”

After the infection, the nurse and forager ants stayed within their cliques and interacted less outside of their work group. The researchers also saw that forager ants spent more time outside of the nest.

“They increase that amount by 15 percent so by quite a long large amount.”

The researchers also measured the amount of fungus on each ant and saw that it was almost completely contained within the foragers group. Some nurse ants and even the Queen did have trace amounts of the fungus’ spores on them but the amount was small enough that they could easily groom them off of their bodies. The study is in the journal Science. [Nathalie Stroeymeyt et al., Social network plasticity decreases disease transmission in a eusocial insect]

Not only does the cliquish behavior stop the spread of the fungus, “but it allows you to develop immunization. Something that’s quite interesting in these ants that’s been shown by other study is that when you receive very small amount of these spores, you don’t have an increase in mortality risk because it’s low enough that you can heal, it’s sort of boost your immune defenses and protect you against later exposure to the same pathogen.

Seems that in their ability to avoid infecting other members of the community, ants may be more advanced than we are.

https://www.scientificamerican.com/podcast/episode/ants-stick-to-cliques-to-dodge-disease/

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Patterns of gene expression unite the prairie vole Microtus ochrogaster with other monogamous species, including certain frogs, fish, and birds. YVA MOMATIUK AND JOHN EASTCOTT/MINDEN PICTURES

By Kelly Servick

In the animal world, monogamy has some clear perks. Living in pairs can give animals some stability and certainty in the constant struggle to reproduce and protect their young—which may be why it has evolved independently in various species. Now, an analysis of gene activity within the brains of frogs, rodents, fish, and birds suggests there may be a pattern common to monogamous creatures. Despite very different brain structures and evolutionary histories, these animals all seem to have developed monogamy by turning on and off some of the same sets of genes.

“It is quite surprising,” says Harvard University evolutionary biologist Hopi Hoekstra, who was not involved in the new work. “It suggests that there’s a sort of genomic strategy to becoming monogamous that evolution has repeatedly tapped into.”

Evolutionary biologists have proposed various benefits to so-called social monogamy, where mates pair up for at least a breeding season to care for their young and defend their territory. When potential mates are scarce or widely dispersed, for example, forming a single-pair bond can ensure they get to keep reproducing.

Neuroscientist Hans Hofmann and evolutionary biologist Rebecca Young at the University of Texas in Austin wanted to explore how the regulation of genes in the brain might have changed when a nonmonogamous species evolved to become monogamous. For example, the complex set of genes that underlie the ability to tolerate the presence of another member of one’s species presumably exists in nonmonogamous animals, but might be activated in different patterns to allow prolonged partnerships in monogamous ones.

“We wanted to be bold—and maybe a little bit crazy” in the new experiment, Hofmann says. Instead of doing a relatively straightforward genetic comparison between closely related species on either side of the monogamy divide, he and colleagues wanted to hunt down a gene activity signature associated with monogamy in males across a wide variety of species—frogs, mice, voles, birds, and fish. So in each of these groups, they selected two species, one monogamous and one nonmonogamous.

Rounding up the brains of those animals took an international team and years of effort. Hostile regional authorities and a complicated permitting system confronted the team in Romania as they tried to capture two types of a native songbird. Hofmann donned scuba gear and plunged into Africa’s Lake Tanganyika to chase finger-length cichlid fish into nets. Delicately debraining them while aboard a rocking boat, he says, was a struggle.

Back the lab, the researchers then grouped roughly comparable genes across all 10 species based on similarities in their sequences. For each of these cross-species gene groups, they measured activity based on how much the cells in the brain transcribed the DNA’s proteinmaking instructions into strands of RNA.

Among the monogamous animals, a pattern emerged. The researchers found certain sets of genes were more likely to be “turned up” or “turned down” in those creatures than in the nonmonogamous species. And they ruled out other reasons why these monogamous animals might have similar gene expression patterns, including similar environments or close evolutionary relationships.

Among the genes with increased activity in monogamous species were those involved in neural development, signaling between cells, learning, and memory, the researchers report online today in the Proceedings of the National Academy of Sciences. They speculate that genes that make the brain more adaptable—and better able to remember—might also help animals recognize their mates and find their presence rewarding.

It makes sense that genes involved in brain development and function would underlie a complex behavior like monogamy, says behavioral neuroscientist Claudio Mello of Oregon Health & Science University in Portland. But because the researchers didn’t dissect out specific brain regions and analyze their RNA production independently, they can’t describe the finely tuned patterns of gene expression in areas that are key to reproductive behavior. “It seems to me unlikely that by themselves these genes will be able to ‘explain’ this behavior,” he says.

“The fact that they got any common genes at all is interesting,” adds Lisa Stubbs, a developmental geneticist at the University of Illinois in Urbana. “It is a superb data set and an expert analysis,” she says, “[but] the authors have not actually uncovered many important biological insights into monogamy.”

The study did turn up a curious outlier. Some of the genes with decreased expression in most of the monogamous species showed increased expression in one of them—the poison dart frog Ranitomeya imitator. Young notes that in this species’s evolutionary history, fathers cared for the young before cooperative parenting evolved. As a result, these frogs may have had a different evolutionary starting point than other animals in the study, later tapping into different genes to become monogamous.

Hoekstra, who has studied the genetics of monogamy in mice, sees “a lot of exciting next steps.” There are likely mutations in other regions of DNA that regulate the expression of the genes this study identified. But it will take more work to show a causal relationship between any particular genetic sequence and monogamous behavior.

People also often opt for monogamy, albeit for a complicated set of social and cultural reasons. So, do we share the gene activity signature common to monogamous birds, fish, and frogs? “We don’t know that,” says Hofmann, but “we certainly would speculate that the kind of gene expression patterns … might [show up] in humans as well.”

http://www.sciencemag.org/news/2019/01/monogamy-may-have-telltale-signature-gene-activity

Activating something called the behavioral immune system puts a damper on dating, new research shows.

About a decade ago, evolutionary psychologists suggested that humans have evolved a first line of defense against disease: this behavioral immune system or BIS.

The theory is that perceiving, rightly or wrongly, the threat of disease unconsciously activates this system. Although we cannot see microorganisms with the naked eye, we are nevertheless able to identify cues—such as coughs, unpleasant smells, or skin lesions—that hint at the possible presence of pathogens, whether or not these are actually present or represent real health threats.

Scientists have suggested that the activation of the BIS leads to prejudiced and avoidant attitudes and behavior towards those who display superficial cues connoting disease.

But how does this affect our dating lives, where two competing needs are pitted against one another—i.e., the potential benefits of connecting and finding a mate versus the need to protect oneself from disease? McGill University scientists set out to find out, by looking at the activation of the BIS in young, single, heterosexual Montrealers in both real speed-dating events and in experimental online dating.

The results were convincing. And not very happy.

“We found that when the behavioral immune system was activated it seemed to put the brakes on our drive to connect with our peers socially,” says first author of the study Natsumi Sawada, who holds a PhD in psychology from McGill University.

“We hadn’t expected this to be the case in real life situations like dating where people are generally so motivated to connect. The results suggest that beyond how we consciously or unconsciously think and feel about each other there are additional factors that we may not be consciously aware of, such as a fear of disease that may influence how we connect with others.”

This video explains how the experiments worked:

The findings appear in the Personality and Social Psychology Bulletin. The Social Sciences and Humanities Research Council (SSHRC) and the Fonds de Recherche sur la Société et la Culture (FRQSC) supported the work.

https://www.futurity.org/behavioral-immune-system-dating-1745362-2/

BY RACHEL EHRENBERG

Getting your groove on solo with headphones on might be your jam, but it can’t compare with a live concert. Just ask your brain. When people watch live music together, their brains waves synchronize, and this brain bonding is linked with having a better time.

The new findings, reported March 27 at a Cognitive Neuroscience Society meeting, are a reminder that humans are social creatures. In western cultures, performing music is generally reserved for the tunefully talented, but this hasn’t been true through much of human history. “Music is typically linked with ritual and in most cultures is associated with dance,” said neuroscientist Jessica Grahn of Western University in London, Canada. “It’s a way to have social participation.”

Study participants were split into groups of 20 and experienced music in one of three ways. Some watched a live concert with a large audience, some watched a recording of the concert with a large audience, and some watched the recording with only a few other people. Each person wore EEG caps, headwear covered with electrodes that measure the collective behavior of the brain’s nerve cells. The musicians played an original song they wrote for the study.

The delta brain waves of audience members who watched the music live were more synchronized than those of people in the other two groups. Delta brain waves fall in a frequency range that roughly corresponds to the beat of the music, suggesting that beat drives the synchronicity, neuroscientist Molly Henry, a member of Grahn’s lab, reported. The more synchronized a particular audience member was with others, the more he or she reported feeling connected to the performers and enjoying the show.

https://www.sciencenews.org/article/brain-waves-concertgoers-sync-shows

Any ad executive will tell you that sex sells. But why? Do sexy images stimulate our biological urges, somehow motivating us to buy products? Or do marketers merely exploit and perpetuate our cultural obsession with sexual imagery? Do people want the beauty, wealth and power celebrities have, and use the products they endorse in the hope of achieving these same qualities?

These explanations are plausible, but my colleagues and I have a new one, based on decades of work comparing the behavior and neurobiology of decision-making in monkeys and people: Our brains have been fine-tuned by evolution to prioritize social information, and this laser focus on others profoundly shapes our decisions.

As early as the 1870s, companies like Pearl Tobacco and later, W. Duke & Sons, employed social advertising, showcasing nude or partially exposed women on posters and trading cards. Although the images had no direct link to the products, sales increased. A century and a half later, it seems impossible to escape sexual imagery in advertising. The same is true for celebrities in marketing campaigns—actors, musicians, athletes, even politicians and business leaders. These celebrities often don’t even use the products they advertise, yet the method still seems to work.

Our brains have circuits specialized for identifying, remembering and inferring the mental states of others so we can predict their behavior and make good decisions. In other words, we’re built to deal with people. But we’re not alone in this connection. Many species of monkeys and apes—our closest living relatives—also live in large, complex, dynamic societies. Behavioral studies show that, like us, these primates identify others, track prior encounters, empathize with friends and relatives, and make inferences about individuals’ mental states.

For people and monkeys alike, it’s important to find a good mate, make powerful allies and avoid potential threats. Paying close attention to social cues can improve these choices. In fact, both men and male monkeys are exquisitely sensitive to indications of female fertility. Men rate ovulating women as more attractive, and tip more for lap dances by fertile women. Similarly, male rhesus macaques prefer images of females with artificially reddened faces and hindquarters, coloration that predicts ovulation and sexual receptivity.

Women and female monkeys are also sensitive to clues about male quality, although what we know about that is based on fewer studies. A woman’s preference shifts toward more masculine faces—broader jaw, wider-set but smaller eyes—during ovulation. Female macaques, when ovulating, tend to mate with higher-ranking males and prefer those with reddened faces caused by a testosterone surge. Other studies found that both people and monkeys pay more attention to high-status individuals and are more likely to follow their gaze.

According to economics, we can quantify how much someone values something—coffee, a magazine—by how much he or she will pay for it. In our latest work, we developed an assessment, dubbed the “pay-per-view” test, to measure subconscious value of visual images. In the experiment, monkeys had the option to forego juice or food for a glimpse at a picture of another monkey. People could choose whether to accept a smaller cash reward to peek at a picture of another individual.

Our findings were striking. Male college students paid slightly more money to view an attractive woman than an unattractive one, losing several dollars during the experiment. Female students were much less motivated to see attractive men. Monkeys of both genders valued sex and status, accepting less food or juice to see images of monkey genitalia and faces of high-status males. In contrast, they required extra food or juice to look at faces of low-status males.

Based on these findings, it’s clear that monkeys and humans value information about sex and status so much that it can replace rewards like food, juice and money. Strong parallels between the two suggest shared brain mechanisms at work.

To test this idea, we used fMRI to scan the brains of male students in two circumstances: one, while they viewed female faces of varying attractiveness, the other while money was either deposited or withdrawn from their study stipend. The sight of attractive faces strongly activated a network of brain areas previously implicated in processing rewards—including the orbitofrontal cortex, ventromedial prefrontal cortex, and medial and ventral striatum—and neural activity increased with increasing attractiveness. The same happened with monetary rewards and losses. We believe this network computes economic “utility,” a person’s internal desire for or satisfaction with a good or service, thought to underlie decisions.

To determine the physiological basis of these signals, we measured individual brain cell activity in monkeys. Some fired strongly when male monkeys chose to see female genitalia, a high-status male face, or a large juice reward, but fired less when they chose low-status faces or small juice rewards. Specific brain cells reacted to images of faces and genitals but not juice, indicating the brain’s reward system possesses dedicated hardware for identifying and prioritizing key social information.

Can these discoveries help explain the power of sex and status in advertising? In theory, ads that associate sex or status with specific brands or products activate the brain mechanisms that prioritize social information, and turning on this switch may bias us toward the product.

To test this idea, we exposed male rhesus macaques to logos of household brands like Nike and Pizza Hut paired with a social image (e.g., female genitalia, high-status male face) or the same image with pixels rearranged to make it unrecognizable but retain the same brightness, contrast, and color, salient cues that could draw attention to a stimulus. Monkeys received a sweet treat for touching the screen after the ad, then had the choice between brands paired with a social image or its scrambled version.

Our advertising campaign was remarkably effective. Monkeys developed preferences for brands linked with sex and status. Both males and females preferred logos paired with sexual cues and the faces of high-status monkeys. And the more often male monkeys saw sexual advertisements, the more they preferred the brands. Sound familiar? Even monkeys, it seems, can be persuaded to choose a brand through social advertising.

Given the nearly identical specializations of brain reward circuits to prioritize social information in monkeys and people, is it any wonder that sex and status sell?

https://blogs.scientificamerican.com/observations/what-monkeys-can-teach-us-about-advertising/

By Richard Kemeny

According to much of the scientific literature, dominance in social animals goes hand-in-hand with healthier lives. Yet leaders of the pack might not be healthier in all aspects, and according to a study published last week (February 26) in Scientific Reports, they are more at risk of parasite infection.

“While high-ranking animals often have the best access to food and mates, these advantages appear to come with strings attached,” says study coauthor Elizabeth Archie, a behavioral and disease ecologist at the University of Notre Dame, in an email to The Scientist. “These strings take the form of higher parasite exposure and susceptibility.”

Lower social status is usually linked to poorer health, according to previous studies. Animals towards the bottom of hierarchies have to struggle more for resources, and are often subjected to aggressive behavior from their superiors. In many species of birds, mice, and nonhuman primates, for instance, poorer physical condition is more common for subordinates. Female macaques of low social status, for example, have been shown to have lower bone density and an increased risk of developing inflammatory diseases.

Yet the relationship between social subordination and infectious disease risk hasn’t been clearly measured, according Archie and her coauthors. To look at the relationship between social status and one particular malady—parasite infections—they carried out a meta-analysis of 39 studies spanning 31 species, searching for patterns of parasitism.

In the majority of studies, those individuals in dominant positions—in particular, dominant males—were found to be more at risk of being infected. The effect was strongest in mammals, and in ordered hierarchical societies where social status is correlated with sexual activity.

These findings support two previous hypotheses about the links between social status and parasitism. One relates infection risk to resource access: exposure to infection is more common when animals feed and mate more. Dominant reindeer, for example, spend more time eating than subordinate individuals, and are more likely to become infected by nematodes. And greater sexual activity brings more risk of transmitted infections. Take, for instance, dominant feral cats, whose sexual proclivity increases the chances of developing Feline Immunodeficiency Virus.

The other hypothesis proposes a trade-off between reproductive effort and immunity to disease. In other words, those in dominant positions expend more energy on mating, and therefore invest less into costly immune defences.

“When you put it in the context [of these hypotheses], it does make a lot of sense,” says Jennifer Koop, a biologist at the University of Massachusetts-Dartmouth, who was not involved in the study.

Archie doesn’t think that individuals will deliberately opt for lower status in order to avoid infection. “High status comes with so many other advantages that the cost of a few more parasites might not be enough for individuals to shun high social status,” she says.

It’s also conceivable that there are benefits to both parasite and host in this relationship, says Nicole Mideo, an evolutionary biologist at the Univeristy of Toronto, who was not involved in the study. “The parasites are exploiting the resources of the host, so if you have a host that doesn’t get access to much food, then the parasite isn’t going to get access to much food,” she says.

This study mostly focused on parasitic worms, a limitation the researchers want to expand beyond. Additionally, the toll on dominant animals’ health of the increased risk of parasite infections was not explored. Mideo explains that there could be subtle advantages here, as research has shown worms can alter immune systems, and might protect against other infections. “It’s entirely possible that having worm infections does confer some sort of advantage in the context of other potential diseases,” she says.

Habig et al., “Social status and parasitism in male and female vertebrates: a meta-analysis,” Scientific Reports, doi:10.1038/s41598-018-21994-7, 2018.

https://www.the-scientist.com/?articles.view/articleNo/52003/title/Social-Dominance-Comes-At-a-Cost/