Author: Roheeni Saxena

In adapting to our environment, we'd ideally use the results of previous actions to inform future choices, updating our expectations and decisions to reflect knowledge gained from earlier experiences. However, sometimes we ignore the past's feedback when we really should pay attention it, leaving us trapped in a series of bad decisions. A study published in PNAS demonstrates that this “bad choice persistence” occurs when changing our decisions would go against our existing biases. This means that our beliefs can trap us in a difficult-to-break bad-decision feedback loop.

To examine this phenomenon, researchers looked at how subjects integrated new experiences with their past history when completing a sensory stimulus task. The participants were asked to predict whether a visual stimulus would appear on the left side or the right side of a screen based on where the stimulus appeared in previous trials.

In the first set of experimental trials, the location of the stimulus was randomized. These trials assessed the subjects’ baseline biases towards choosing one side of the screen or the other. After establishing these biases, the participants began a second set of experimental trials. In these experiments, the stimulus' location was determined by a probabilistic model that set the odds of its location using both the participants' previous choice history and the item's previous locations.

The oxygen minimum zone is the section of ocean that has the lowest oxygen saturation. While the thickness and depth of the OMZ varies, the Pacific Ocean's OMZ has been expanding in recent years. This has consequences for oceanic ecosystems, since animals struggle in this region, and its primary productivity is low. However, the cause of this oxygen decline is not fully understood. A paper published in Nature Geoscience uses climate modeling to indicate that aerosol particulate pollution may be contributing significantly to the acceleration of oxygen depletion.

To determine the relationship among atmospheric pollution, ocean dynamics, and the OMZ, researchers performed computational simulations of atmospheric chemistry and its impact on marine biochemistry. This modeling included fluctuations of aerosols that contained soluble iron and fixed nitrogen, coupled with a dust-iron dissolution scheme. The model also included hindcast simulations that tracked anthropogenic pollution increases between the years of 1750 and 2002.

The researchers’ model showed that the combination of climate variability and longterm increases in macro- and micronutrients going into the ocean alters the large-scale patterns of ocean productivity and dissolved oxygen. They also saw that variability in ocean circulation and pollution enhanced the deposition of soluble iron, whereas fixed nitrogen did not see the same effect.

Most modern conflicts are civil wars—wars that tear countries apart, sometimes even pitting friends and family against each other. After the fighting dies down, nations are left with a divided populace and are faced with the difficult task of reconciliation. A study published in Science magazine found that post-war reconciliation efforts can lead to an increase in national social capital, but this benefit comes at the expense of individual citizens’ psychological well being.

The researchers examined the consequences of a truth and reconciliation effort in Sierra Leone using a randomized controlled trial approach. The recent civil conflict in Sierra Leone resulted in more than fifty thousand deaths, and more than half of the population was displaced. Violence occurred between neighbors within the same village, and the rebel group frequently recruited and deployed child soldiers.

After the war, the new government set up a national truth and reconciliation program, but this program only covered a small fraction of the war-related trauma. To study the effects of these types of programs, the researchers implemented their own truth and reconciliation effort. It was built around forums where victims of the civil war could describe the violence that they had experienced, and the perpetrators of these crimes could seek forgiveness for their actions.

Male competitiveness is pretty engrained in our culture, with popular images of it encompassing everything from sports to business to the PlayStation. And there are some studies that have shown men to be more competitive than women, but this effect hasn’t been studied all that deeply. A new paper published in PNAS shows that gender’s effects on competitiveness go away when the stakes of the competition are related to children’s benefit, rather than personal gain. When children are at stake, women and men are equally competitive.

The study is based on the idea that women aren’t necessarily less competitive than men, but there are gender-specific spheres of competition. The authors hypothesized that one of those spheres involves offspring. To test this hypothesis, the researchers asked participants of both genders to perform tasks under two different reward schemes. In the first reward scheme, participants received cash, a standard incentive in psychology experiments. In the second reward scheme, participants received a scholastic bookstore voucher worth the same value. This voucher was a proxy for children’s benefit.

This study was conducted in China, and all participants were parents of school-aged students. The authors think that Chinese culture’s heavy emphasis on education makes it more likely that the participants would see a “scholastic bookstore voucher” as something that would benefit their child. This expectation was confirmed via interviews with local teachers and parents, who agreed that Chinese participants would likely use a scholastic bookstore voucher to buy educational books for their children.

The HPV vaccine provides effective protection from the human papilloma virus and the cancers it can induce. Because HPV is transmitted sexually, inclusion in mandatory vaccination schedules has been a controversial issue, and legislation varies by state. Complicating matters further, companies have continued to improve the vaccine, expanding the list of viral strains that it protects against. A new study in PNAS finds that having states require the latest, most protective HPV vaccine for girls and boys would be highly cost-effective and would lead to better health outcomes at the national level.

HPV is the most prevalent sexually transmitted infection in the US, with over 100 viral strains circulating in the population. Over half of cervical cancer cases in the US are thought to be caused by HPV, which can also cause vaginal cancer, penile cancer, anal cancer, and cancers of the mouth and throat.

Fortunately, several vaccines for HPV are now available, including bivalent, quadrivalent, and nonavalent—these protect against two, four, and nine strains of HPV respectively. These vaccines can protect women from 66-81 percent of cervical cancers, depending on the number of strains that are included in the formulation.

Unemployment obviously has economic effects on people, but it can also have psychological impacts, sometimes triggering depressive episodes. However, until now, there has been no quantitative research evaluating consequences of unemployment on people’s feelings about money. A study published in PNAS finds that unemployment changes how people think about entitlement.

The study defines entitlement as the acknowledgement that someone has a right to keep, consume, or dispose of things that they have earned, including their salary. The idea of entitlement is important for understanding the labor market and workers’ self-interest. Generally, people who earn a higher income tend to be more self-interested, with minimal preference for wealth redistribution, whereas lower-income individuals tend to think that wealthier people should pay more taxes and poorer people should be eligible for social support.

The study examined participants’ attitudes on wealth redistribution and wealth entitlement twice, with a year-long gap between experiments. This setup allowed the researchers to study people who transitioned between various states of employment in the interim. The study was conducted in Spain, which has the third highest unemployment rate in the Organization for Economic Cooperation and Development. The attrition rate was 48 percent between the two experiments, and this paper focuses on 151 participants who were either employed or students for both experiments, or employed/students for the first experiment and unemployed for the second.

In 2015, a study was published that claimed that reducing prejudice against homosexual people was relatively easy. All it took was a brief conversation with a stranger who was going door to door talking about prejudice against homosexuals. Supposedly, participants’ attitudes remained changed up to three months after said conversation.

The study received widespread media coverage and was considered groundbreaking because we knew so little about how to reduce prejudice. Unfortunately, it turned out to be built largely on fraudulent data, and the study was retracted.

Ironically, the researcher who uncovered the fraudulent data in this first canvassing study, David Broockman, has now published his own study on the same issue. It demonstrates that canvassing actually does change participants’ attitudes toward transgender individuals and that this change in attitudes persists for at least three months.

Personal biases held by physicians and others in the field of healthcare continue to affect patients of all kinds. These can be biases about specific diseases or treatments, or biases about the patients themselves.

Pain management is one area in which racial disparities have been widely documented but haven’t been fully understood. A new study published in PNAS indicates that incorrect beliefs about racial differences cause white doctors and medical students to make less-appropriate pain-treatment recommendations. In short, black patients may be getting short-changed on pain management if their doctors think that black bodies are inherently stronger than white bodies.

To study the phenomenon of racial bias in pain treatment, the researchers conducted two studies. They first examined the beliefs of whites who were not medical professionals to establish baseline prejudices about pain perception for people of different backgrounds. They found that white adults with no medical training endorse at least some false beliefs about biological differences with black people, including the incorrect belief that blood coagulates at different speeds for people of different races.

Attraction is a mysterious phenomenon that science keeps trying to decode. We have examined the neurochemicals that may be associated with personal chemistry, we have conducted experiments to see if we can make people fall in love, and major online dating sites mine their data to look for patterns among potential matches. A recent article published in PNAS adds a new piece of information to the scientific puzzle: humans tend to be more attracted to other people who take up more space.

These results echo earlier findings that suggest “power poses” can help individuals feel more confident—perhaps a similar phenomenon makes people who engage in dominant non-verbal displays more attractive to potential mates.

For this paper, researchers conducted two field studies in which they tracked nonverbal behaviors that might be associated with attraction and dominance. The first study took place in a speed-dating setting and was an observational study in which the researchers simply watched daters’ behavior. The second study was experimental; it tracked participants’ romantic attraction to potential matches presented by a freely available GPS-based dating app in the San Francisco area (presumably something similar to dating apps like Tinder or OKCupid).

Memories allow us to record and store information, a central feature of our lives. Since the groundbreaking case of HM, a patient who lost the majority his hippocampus, we’ve known that this brain structure is central to forming long-term episodic memories. But we’re still unsure about how the neurons of the hippocampus change at the cellular level to lock those memories in place. A new paper published in Science provides a new insight on this: two different types of neurons, with different activity and adaptability, are both needed to handle memories.

The researchers behind the new study tracked the neural firing patterns of rats that were placed in mazes and allowed to find their way out. The authors were most interested in examining a type of neuron known as a “place cell.” These place cells are hippocampal neurons that are activated when the rat finds itself in a particular place—they play a role in orienting the animal to its environment. Critically, these cells are central to recalling memories—both positive and negative—associated with a location.

The researchers studied these neurons in rats that navigated around a maze, and as they took a post-maze nap to allow them to consolidate their new memories. The authors were interested in a phenomenon called sleep-related hippocampal sharp wave ripples among these rats.