Do estrogen levels affect the willingness to share?

Date:September 17, 2015

Source:Goethe-Universität Frankfurt am Main

Summary:Fluctuating hormone levels change a woman’s social behaviour over the course of the menstrual cycle. Mood swings and irritability before the period as well as a greater interest in sex during ovulation are well known. Now psychologists have discovered that the willingness to share one’s own resources with strangers also fluctuates with hormone levels. Women exhibit a higher willingness to cooperate during and shortly after menstruation — this is the result of two online studies involving over 400 German and US American women.

To qualify for the study, the participants had to have a natural menstrual cycle, in other words not be using hormone-based contraceptives, had to not be pregnant and not have entered menopause yet. The researchers compared the willingness to cooperate between women in the time during and shortly after menstruation (early follicular phase), when the levels of the hormones estrogen and progesterone are low, and a few days after ovulation (midluteal phase), when the estrogen and progesterone levels are especially high. The hormone levels were estimated based on the self-reported day in the cycle.

The researchers measured the subjects’ individual willingness to cooperate using a well-established psychological scale, the “Social Value Orientation.” To do so, they asked the women to divide fictitious money between themselves and another person who was a complete stranger to them.

“Numerous studies have shown that people who exhibit a high willingness to share in this test also donate money more often and in larger amounts in real life, take the train instead of the car to work more often and are more willing to compromise in negotiations than people with a less pronounced pro-social value orientation,” Christine Anderl, lead author of the study, explains.

The two studies showed that the women were significantly more inclined to share their own resources with a stranger during and shortly after menstruation than they were a few days after ovulation.

The greater the cycle-dependent level of the “female” sex hormone estrogen, the lower the willingness to share of the women on a purely statistical basis. “While we are firmly convinced that the variation in the willingness to share over the course of the cycle is a real and systematic effect, we still have to determine whether or not it is really caused by estrogen as the present data suggest,” Christine Anderl tells us.

“This matches the findings of other research groups, who were able to show that hormones such as oxytocin and the “male” sex hormone testosterone affect the willingness to cooperate in humans,” Prof. Sabine Windmann from the Institute for Experimental Psychology 2 at the Goethe University commented. How strongly the cycle-dependent fluctuations in the willingness to cooperate affect the day-to-day life of women and which areas of life are particularly affected by this will have to be researched in further studies.

However, the researchers have already found initial evidence which suggests that the described effects also occur when the subjects are using real money. These results are also interesting in light of hormonal contraception. Little is currently known about how synthetic hormones act on the receptors in the brain and what effect they have on the behaviour of women.


Story Source:

The above post is reprinted from materials provided by Goethe-Universität Frankfurt am Main. Note: Materials may be edited for content and length.


Journal Reference:

  1. Anderl, C., Hahn, T., Notebaert, K., Klotz, C., Rutter, B., & Windmann, S. Cooperative preferences fluctuate across the menstrual cycle. Judgment and Decision Making, Vol. 10, No. 5, September 2015, pp. 400-406

Environmental Factors Determine Whether Immigrants Are Accepted by Cooperatively Breeding Animals

Feb. 6, 2013 — Cichlid fish are more likely to accept immigrants into their group when they are under threat from predators and need reinforcements, new research shows. The researcher suggests that there are parallels between cooperatively breeding fish’s and humans’ regulation of immigrants. The research was published February 6, 2013, in the journalProceedings of the Royal Society B.


The Princess of Lake Tanganyika (Neolamprologus pulcher), a cichlid fish which is popular in home aquariums, are cooperatively breeding fish with a dominant breeding pair and several ‘helper’ fish that do not normally breed but instead assist with raising offspring. Helpers also play a crucial role in defending the group’s territory against outsiders — although helpers also compete with the breeders for resources and reproductive opportunities.

The researchers, led by Dr Markus Zӧttl of the University of Cambridge, wanted to find out how environmental pressures might influence the acceptance of new immigrants. Zӧttl, who conducted the research while at the University of Bern, said: “All animal societies are affected in one or another by immigration and when we seek to understand social organisation we need to understand which environmental factors influence processes like immigration.”

A subdivided tank was used to carry out a series of tests in which different scenarios were observed. For the study, a breeding pair (which would be responsible for deciding whether a newcomer would be allowed to join the group) was placed in one compartment next to a compartment containing either a fish predator, an egg predator, a herbivore fish or no fish at all. An immigrant was placed in a third, adjoining compartment. The breeding pair was then exposed to the different fish in compartment two. The researchers then observed whether the type of fish they were exposed to would affect whether they accepted the immigrant fish from the third compartment.

The researchers found that breeders are less aggressive to immigrants and more likely to accept the unknown and unrelated fish as a member of their group when they are simultaneously exposed to predators. They concluded that cichlid fish are more likely to accept immigrants into their group when they are under threat from predators and can be used to increase their defences.

Dr Zӧttl added: “Our fish resemble human societies’ view of immigration in two crucial aspects: The need for help in the territory takes precedence, and it seems to be a strategy of the territory holders to accept immigrants only when they need assistance with territory defence. This resembles human societies which organise immigration according to the demand in the society by encouraging skilled immigration when certain types of labour are in short supply.”

The researchers also found that the fish appear to consider future threats. When egg predators were presented to a breeding pair who had not yet spawned they accepted new incomers. Their acceptance of reinforcements in the form of immigrant fish suggests that that the egg predator was viewed as a threat.

Dr Zӧttl concluded: “This behaviour suggests that breeders of this species might be able to anticipate a potential threat — and it seems to resemble the future planning evident in birds and apes.”


Story Source:

The above story is reprinted from materials provided byUniversity of Cambridge. The original story is licensed under a Creative Commons license.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


University of Cambridge (2013, February 6). Environmental factors determine whether immigrants are accepted by cooperatively breeding animals. ScienceDaily. Retrieved February 7, 2013, from http://www.sciencedaily.com/releases/2013/02/130206094716.htm

Cooperators Can Coexist With Cheaters, as Long as There Is Room to Grow

Feb. 1, 2013 — Microbes exhibit bewildering diversity even in relatively tight living quarters. But when a population is a mix of cooperators, microbes that share resources, and cheaters, those that selfishly take yet give nothing back, the natural outcome is perpetual war. A new model by a team of researchers from Princeton University in New Jersey and Ben-Gurion University in Israel reveals that even with never-ending battles, the exploiter and the exploited can survive, but only if they have room to expand and grow.


 

The researchers present their findings at the 57th Annual Meeting of the Biophysical Society (BPS), held Feb. 2-6, 2013, in Philadelphia, Pa.

“In a fixed population, cells that share can’t live together with cells that only take,” said David Bruce Borenstein, a researcher at Princeton. “But if the population repeatedly expands and contracts then such ‘cooperators’ and ‘cheaters’ can coexist.”

Our world and our bodies play host to a vast array of microbes. On our teeth alone, there are approximately a thousand different kinds of bacteria, all living in very close quarters. This is amazing, the researchers observe, because many of those species share resources with nearby neighbors, who might not be so cooperative or even related [1].

At the scale of cells, individuals cooperate mainly by exporting resources into the environment and letting them float away. “This is a deceptively complex process in which cells interact at long ranges, but compete only with nearby individuals,” explained Borenstein. “Our models predict that, even when this exploitation prevents any possibility of peaceful coexistence, the exploiter and the exploited can survive across generations in what is basically a perpetual war.” The researchers speculate that similar competition might occur between cancer cells and normal tissue.

Borenstein and his colleagues made their conclusions based on a computer model that considered two types of cells, cooperators and cheaters, and laid them out on a grid. Cooperators were given the ability, not uncommon in nature, to make a resource that speeds up growth in both kinds of cells. Producing this resource slowed down the growth of cooperators, because they have to divert some energy to resource production. This resource then spread out from the cooperator by diffusion, so that the cells closest to a producer have the greatest resource access. The model revealed that the producers tended to cluster, meaning that being a producer gave you greater access to resources. It also meant that even though cheaters are avoiding the cost of production, they pay for it with reduced resource access.

Within these basic constraints it was found that when the two populations must compete directly for survival, no coexistence is possible. “One type always wins out,” observed Borenstein. However, when the two populations can grow into empty space, the researchers found a strange and paradoxical interaction: cheaters may be outcompeting cooperators locally, even as cooperators grow better overall. These complex interactions may play an important role in the maintenance of diverse microbial communities, like those seen in the mouth.

“To our astonishment, we found that while cheaters can exploit cooperators, cooperators can isolate cheaters, just from cooperation and growth,” concludes Borenstein. “As a result, the community can persist in a sort of perpetual race from which a winner need not emerge.”

[1] J. M. ten Cate. “Biofilms, a new approach to the microbiology of dental plaque.” Odontolgy 2006(94):1-9.

 

Story Source:

The above story is reprinted from materials provided byBiophysical Society, via Newswise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Biophysical Society (2013, February 1). Cooperators can coexist with cheaters, as long as there is room to grow. ScienceDaily. Retrieved February 3, 2013, from http://www.sciencedaily.com/releases/2013/02/130201095947.htm

Note: If no author is given, the source is cited instead.

 

Benefits of Social Grooming in Wild Chimpanzees: Hormone Oxytocin Facilitates Cooperation

Jan. 23, 2013 — Animals which maintain cooperative relationships show gains in longevity and offspring survival. However, little is known about the cognitive or hormonal mechanisms involved in cooperation. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have now found that cooperative relationships are facilitated by an endocrinological mechanism involving the hormone oxytocin, even when these are between non-kin.


They collected urine samples of 33 chimpanzees from Budongo Forest, Uganda, and measured their urinary oxytocin levels after single episodes of a specific cooperative behavior, mutual grooming. The result: Oxytocin levels were higher after grooming with cooperation partners compared with non-cooperation partners or after no grooming, regardless of genetic relatedness or sexual interest. This suggests that in chimpanzees oxytocin, which acts directly on neural reward and social memory systems, plays a key role maintaining social relations beyond genetic ties and in keeping track of social interactions with multiple individuals over time.

In non-human primates and other social animals strong and enduring social bonds are typically seen between genetically related individuals but also, occasionally, between non-kin, same-sex individuals. Although such relationships are typically defined by high rates of cooperative behaviors, how they are maintained over time is still unclear. In humans and other social mammals the neuropeptide hormone oxytocin plays a central role in facilitating bonding between kin and mating partners. Catherine Crockford, Roman Wittig and colleagues of the Max Planck Institute for Evolutionary Anthropology have now analyzed the role of this hormone in the social relationships between wild chimpanzees.

To this end the researchers observed social interactions – like mutual grooming – in a group of wild chimpanzees from Budongo Forest in Uganda and non-invasively collected urine samples of the 33 female and male adult group members on plastic bags or leaves. They determined the level of the hormone oxytocin before and shortly after the animals had been grooming with each other and found that oxytocin levels were especially high in chimpanzees who had been grooming with a “bond partner”,  a cooperation partner, irrespective of whether this bond partner happened to be their kin or not. On the other hand, the level of urinary oxytocin was much lower in chimpanzees who had been grooming with a “non-bond partner”, with whom they did not share a cooperative relationship, or in animals who had not been grooming at all. Furthermore, the researchers found that the animal’s sex or age, grooming duration and other factors did not have a significant influence on urinary oxytocin levels.

“Our results demonstrate that a rise in oxytocin was dependent upon the combined effects of social grooming with a bond partner”, says Catherine Crockford of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “Crucially, oxytocin levels were similarly high after grooming with non-kin and kin bond partners. This suggests that, in chimpanzees, oxytocin plays a key role in maintaining social relations beyond immediate genetic ties”.

“This is the first study that measures the levels of the hormone oxytocin on wild animals in a non-invasive way”, says Roman Wittig of the Max Planck Institute for Evolutionary Anthropology. “We have developed a tool with which cross-species comparisons that link underlying physiology and behavior can eventually be made of social mammals in their natural environment”. In future field research this tool will be used to compare single behaviors – like other cooperative  or aggressive behaviors–by measuring how they differ from each other hormonally.

 

Story Source:

The above story is reprinted from materials provided byMax-Planck-Gesellschaft.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. C. Crockford, R. M. Wittig, K. Langergraber, T. E. Ziegler, K. Zuberbuhler, T. Deschner. Urinary oxytocin and social bonding in related and unrelated wild chimpanzees.Proceedings of the Royal Society B: Biological Sciences, 2013; 280 (1755): 20122765 DOI: 10.1098/rspb.2012.2765
Max-Planck-Gesellschaft (2013, January 23). Benefits of social grooming in wild chimpanzees: Hormone oxytocin facilitates cooperation. ScienceDaily. Retrieved January 28, 2013, from http://www.sciencedaily.com/releases/2013/01/130123094251.htm