Gender bias when evaluating people

Wonkblog reports on a new study on gendered bias: The remarkably different answers men and women give when asked who’s the smartest in the class

Anthropologist Dan Grunspan was studying the habits of undergraduates when he noticed a persistent trend: Male students assumed their male classmates knew more about course material than female students — even if the young women earned better grades. 

“The pattern just screamed at me,” he said. 

So, Grunspan and his colleagues at the University of Washington and elsewhere decided to quantify the degree of this gender bias in the classroom. 

After surveying roughly 1,700 students across three biology courses, they found young men consistently gave each other more credit than they awarded to their just-as-savvy female classmates. 

Men over-ranked their peers by three-quarters of a GPA point, according to the study, published this month in the journal PLOS ONE. In other words, if Johnny and Susie both had A's, they’d receive equal applause from female students — but Susie would register as a B student in the eyes of her male peers, and Johnny would look like a rock star.

It is a pretty good article, and well worth the read - as is the actual paper in PLOS One

Males Under-Estimate Academic Performance of Their Female Peers in Undergraduate Biology Classrooms

Women who start college in one of the natural or physical sciences leave in greater proportions than their male peers. The reasons for this difference are complex, and one possible contributing factor is the social environment women experience in the classroom. Using social network analysis, we explore how gender influences the confidence that college-level biology students have in each other’s mastery of biology. Results reveal that males are more likely than females to be named by peers as being knowledgeable about the course content. This effect increases as the term progresses, and persists even after controlling for class performance and outspokenness. The bias in nominations is specifically due to males over-nominating their male peers relative to their performance. The over-nomination of male peers is commensurate with an overestimation of male grades by 0.57 points on a 4 point grade scale, indicating a strong male bias among males when assessing their classmates. Females, in contrast, nominated equitably based on student performance rather than gender, suggesting they lacked gender biases in filling out these surveys. These trends persist across eleven surveys taken in three different iterations of the same Biology course. In every class, the most renowned students are always male. This favoring of males by peers could influence student self-confidence, and thus persistence in this STEM discipline.

The paper doesn't really tell anything new - it is well documented that there is a gender-bias against women when evaluating performance and skills, especially in science - see e.g. Science faculty’s subtle gender biases favor male students

Despite efforts to recruit and retain more women, a stark gender disparity persists within academic science. Abundant research has demonstrated gender bias in many demographic groups, but has yet to experimentally investigate whether science faculty exhibit a bias against female students that could contribute to the gender disparity in academic science. In a randomized double-blind study (n = 127), science faculty from research-intensive universities rated the application materials of a student—who was randomly assigned either a male or female name—for a laboratory manager position. Faculty participants rated the male applicant as significantly more competent and hireable than the (identical) female applicant. These participants also selected a higher starting salary and offered more career mentoring to the male applicant. The gender of the faculty participants did not affect responses, such that female and male faculty were equally likely to exhibit bias against the female student. Mediation analyses indicated that the female student was less likely to be hired because she was viewed as less competent. We also assessed faculty participants’ preexisting subtle bias against women using a standard instrument and found that preexisting subtle bias against women played a moderating role, such that subtle bias against women was associated with less support for the female student, but was unrelated to reactions to the male student. These results suggest that interventions addressing faculty gender bias might advance the goal of increasing the participation of women in science.

Or How stereotypes impair women’s careers in science

 Women outnumber men in undergraduate enrollments, but they are much less likely than men to major in mathematics or science or to choose a profession in these fields. This outcome often is attributed to the effects of negative sex-based stereotypes. We studied the effect of such stereotypes in an experimental market, where subjects were hired to perform an arithmetic task that, on average, both genders perform equally well. We find that without any information other than a candidate’s appearance (which makes sex clear), both male and female subjects are twice more likely to hire a man than a woman. The discrimination survives if performance on the arithmetic task is self-reported, because men tend to boast about their performance, whereas women generally underreport it. The discrimination is reduced, but not eliminated, by providing full information about previous performance on the task. By using the Implicit Association Test, we show that implicit stereotypes are responsible for the initial average bias in sex-related beliefs and for a bias in updating expectations when performance information is self-reported. That is, employers biased against women are less likely to take into account the fact that men, on average, boast more than women about their future performance, leading to suboptimal hiring choices that remain biased in favor of men.

What I find interesting with the newest study, however, is that it seems like it mostly affects men, while women tend to be better at giving a correct evaluation of the skills of their peers.

If this tendency continues after leaving the classroom (and other studies strongly indicate that this is so), this means that men are more likely to hire less qualified men than the more qualified women, while believing that they are hiring the most qualified person.

Women on the other hand, is more likely to hire the most qualified person, regardless of gender.

When people argue against quotas and other measures to create a level playing field on the job market, they usually argue that the most qualified person should be hired to a given job - well, this study clearly shows that in order for this to happen, there has to be more women involved in the hiring, since otherwise the less qualified men will get hired. 

In other words, in order for people to really get hired on the basis of their merits, we have to break the cycle of hiring based on biases.

So, maybe quotas and other measures are the real way of ensuring people getting hired on the basis of their merit?

Invasive species implicated in killing prehistoric animals

New findings show that it's likely that an invasive species killed off large marsupial species in prehistoric Australia.

What invasive species would that be? Home sapient, the most invasive around.

ScienceDaily has the story.

Humans Implicated In Prehistoric Animal Extinctions With New Evidence

Research led by UK and Australian scientists sheds new light on the role that our ancestors played in the extinction of Australia's prehistoric animals. The new study provides the first evidence that Tasmania's giant kangaroos and marsupial 'rhinos' and 'leopards' were still roaming the island when humans first arrived.

The findings suggest that the mass extinction of Tasmania's large prehistoric animals was the result of human hunting, and not climate change as previously believed.

While the ScienceDaily article makes it sound like this is amazing news, but the idea of a human cause of the megafauna's extinction is hardly a novel idea, and it has certainly been investigated before. PNAS had a good overview article on it back in 2002 Explaining the Pleistocene megafaunal extinctions: Models, chronologies, and assumptions by Brook and Bowman.

The focus of these investigations have mostly focused on whether there were an overlap of human and megafauna inhabitation of Australia, but other studies have shown that even if there were, the extinction might still be at least partly caused by climate changes - see e.g Prolonged coexistence of humans and megafauna in Pleistocene Australia (.pdf) by Trueman et al.

According to the ScienceDaily article, new findings puts humans as the culprits.

Previous research by Professor Flannery and Professor Bert Roberts of the University of Wollongong, Australia, has shown that 90 per cent of mainland Australia's megafauna disappeared about 46,000 years ago, soon after humans first settled the continent. But humans did not reach Tasmania until a few thousand years later, when the island became connected to the mainland by a land bridge as sea levels fell during the last glaciation. "The Tasmanian results echo those on mainland Australia, putting humans squarely back in the frame as the driving force behind megafaunal extinction", said Professor Roberts.

It should perhaps be pointed out that human driven extinction could be cause indirectly, e.g. through changes to the living habitats by the burning of forests etc. or by animals brought along by the humans (e.g. dingos).

Unfortunately it appears that the study the ScienceDaily article refers to haven't appeared online yet - it should be published in the Proceedings of the National Academy of Sciences of the USA (PNAS), so I expect it to be only a matter of time before it's available (though probably behind a paywall).

While looking after the article, however, I did come across to one that's seems somewhat related:
Species invasions and extinction: The future of native
biodiversity on islands (.pdf) by Sax and Gaines. It does address the role of humans in the recent extinction of species.

Better understanding of mammalian hearing

I had the impression that the hows and whys of hearing was pretty much known, at least when it came to mammals, but a new discovery shows that I was wrong about that.

ScienceDaily reports on it.

New Hearing Mechanism Discovered

MIT researchers have discovered a hearing mechanism that fundamentally changes the current understanding of inner ear function. This new mechanism could help explain the ear's remarkable ability to sense and discriminate sounds. Its discovery could eventually lead to improved systems for restoring hearing.

MIT Professor Dennis M. Freeman, working with graduate student Roozbeh Ghaffari and research scientist Alexander J. Aranyosi, found that the tectorial membrane, a gelatinous structure inside the cochlea of the ear, is much more important to hearing than previously thought. It can selectively pick up and transmit energy to different parts of the cochlea via a kind of wave that is different from that commonly associated with hearing.

The article explains in some detail how this discovery differentiates from our former knowledge.

It has been known for over half a century that inside the cochlea sound waves are translated into up-and-down waves that travel along a structure called the basilar membrane. But the team has now found that a different kind of wave, a traveling wave that moves from side to side, can also carry sound energy. This wave moves along the tectorial membrane, which is situated directly above the sensory hair cells that transmit sounds to the brain. This second wave mechanism is poised to play a crucial role in delivering sound signals to these hair cells.

In short, the ear can mechanically translate sounds into two different kinds of wave motion at once. These waves can interact to excite the hair cells and enhance their sensitivity, "which may help explain how we hear sounds as quiet as whispers," says Aranyosi. The interactions between these two wave mechanisms may be a key part of how we are able to hear with such fidelity - for example, knowing when a single instrument in an orchestra is out of tune.

It's always fascinating when scientists expand on our knowledge, especially so when it's on our knowledge of how the body functions.

The research has been published in Proceedings of the National Academy of Sciences (with the graduate student as the first-name author), and it's a featured article, so it's available for free.

Longitudinally propagating traveling waves of the mammalian tectorial membrane

Is walking upright more energy efficient?

ScienceDaily reports on a new study that gives some evidence for the hypothesis that walking on two legs is more energy efficient than than dragging your knuckles while walking.

Study Identifies Energy Efficiency As Reason For Evolution Of Upright Walking

A new study provides support for the hypothesis that walking on two legs, or bipedalism, evolved because it used less energy than quadrupedal knucklewalking.

When I read that last night, while rather tired, my first thought was that that it sounded inplausible - if walking upright is more energy efficient, then why don't most mammals walk on two legs. Rereading it today, I of course realized that walking upright, like a Home Sapiens, is more energy efficient than walking on your legs and knuckles, like our fellow apes does. That doesn't mean that it's necessarily more efficient than walking on four legs, like the majority of mammals do.

Bipedalism marks a critical divergence between humans and other apes and is considered a defining characteristic of human ancestors. It has been hypothesized that the reduced energy cost of walking upright would have provided evolutionary advantages by decreasing the cost of foraging.

"For decades now researchers have debated the role of energetics and the evolution of bipedalism," said Raichlen. "The big problem in the study of bipedalism was that there was little data out there."

The researches collected metabolic, kinematic and kenetic data from five chimpanzees and four adult humans walking on a treadmill. The chimpanzees were trained to walk quadrupedally and bipedally on the treadmill.

Humans walking on two legs only used one-quarter of the energy that chimpanzees who knuckle-walked on four legs did. On average, the chimpanzees used the same amount of energy using two legs as they did when they used four legs. However, there was variability among chimpanzees in how much energy they used, and this difference corresponded to their different gaits and anatomy.

Interesting result, and it certainly explains why bipedalism became the movement of choice for Homo Sapiens and our ancestors. Or at least, it does so, once we moved down from the trees - I would expect that if we looked at movement in trees, the energy use would be somewhat reversed.

The study is published in PNAS, but unfortunately it's behind a pay-wall. The abstract can be found here though.

Two interesting articles from PNAS

While looking for the article about the early panda mentioned in my last post, I came across a couple of interesting articles at Proceedings of the National Academy of Sciences that were open access.

One of them is about how geographic range affects the risk of extinction.

Wide geographic range is generally thought to buffer taxa against extinction, but the strength of this effect has not been investigated for the great majority of the fossil record. Although the majority of genus extinctions have occurred between major mass extinctions, little is known about extinction selectivity regimes during these "background" intervals. Consequently, the question of whether selectivity regimes differ between background and mass extinctions is largely unresolved. Using logistic regression, we evaluated the selectivity of genus survivorship with respect to geographic range by using a global database of fossil benthic marine invertebrates spanning the Cambrian through the Neogene periods, an interval of {approx}500 My. Our results show that wide geographic range has been significantly and positively associated with survivorship for the great majority of Phanerozoic time. Moreover, the significant association between geographic range and survivorship remains after controlling for differences in species richness and abundance among genera. However, mass extinctions and several second-order extinction events exhibit less geographic range selectivity than predicted by range alone. Widespread environmental disturbance can explain the reduced association between geographic range and extinction risk by simultaneously affecting genera with similar ecological and physiological characteristics on global scales. Although factors other than geographic range have certainly affected extinction risk during many intervals, geographic range is likely the most consistently significant predictor of extinction risk in the marine fossil record.

So, in other words, animals that live in large geographical range are less likely to become extinct than animals that live in a narrow geographical range. This is less notable during mass extinction (i.e. times where large numbers of species go extinct), but even then it can be measured.

This is something that was expected, but undocumented until now.

The other article, is also something that follows quite logically from what we know. It shows that resources have an influence on biodiversity

I probably explained the findings incorrectly, and would love to see any of the real biologist out there (e.g. Coturnix or PZ Myers) explain these papers to the rest of us.

I wonder if Amanda has any comments....

I could help thinking of Pandagon when I saw this bit of news on ScienceDaily

Remains Of Earliest Giant Panda Discovered

Although it may sound like an oxymoron, a University of Iowa anthropologist and his colleagues report the first discovery of a skull from a "pygmy-sized" giant panda -- the earliest-known ancestor of the giant panda -- that lived in south China some two million years ago.

The remains were found 18 months ago, and shows that pandas have remained relatively unchanged through the last couple of million years, both in regards to anatomy and to diet.

"Pandas are very unique bears --- the only bear species that is known to exist wholly on a vegetarian diet," says Ciochon. "The evolution of this unique dietary specialization probably took millions of years to refine. Our new discovery shows the great time depth of this unique bamboo-eating specialization in pandas. Thus, pandas have been 'uniquely pandas' for many millions of years says Ciochon."

Ciochon says that the find further helps establish conditions that existed in the region during the varying climatic conditions of the Pliocene and Pleistocene epochs, stretching back some three millions years before the present. The pygmy giant panda lived in lowland tropical bamboo forests. It is often found associated with the extinct elephant-like creature, Stegodon, and the giant extinct ape, Gigantopithecus. Today's giant panda is isolated in mountainous upland bamboo forests, partly due to the pressure of modern civilization.

The article was brought in the June 18-22 online issue of Proceedings of the National Academy of Sciences, but unfortunately it's behind a paywall.

Are chimps more advanced than humans?

Well, yes, if you are talking about which species that has gone through most positive selection on genes, according to a new study published in the Proceedings of the National Academy of Sciences, and reported on by ScienceDaily.

Put a human and a chimpanzee side by side, and it seems obvious which lineage has changed the most since the two diverged from a common ancestor millions of years ago. Such apparent physical differences, along with human speech, language and brainpower, have led many people to believe that natural selection has acted in a positive manner on more genes in humans than in chimps.

But new research at the University of Michigan challenges that human-centered view. "We often think that we're unique and superior to other species, so there must be a lot of Darwinian selection behind our origin," said Jianzhi (George) Zhang, associate professor of ecology and evolutionary biology. "However, we found that more genes have undergone positive selection in chimpanzee evolution than in human evolution."

When looking at species and their development, it is natural to hold an anthropocentric view, where you regard your own species as the pinnacle of evolution. However, this view is unfounded, since you cannot consider any evolutionary process better than the other, as long as it result in the survival of a species. The is no doubt that Homo sapiens is among the most adaptive and succesful species on our planet, but so you could say about Rattus rattus (the black rat) or cockroaches.

This research shows that humankind can be considered less advanced, evolution wise, than chimpanzees. Something that quite a few people will probably have some problems accepting, even if they accept evolution. Such problems doesn't not change the facts though, and it might lead to a more healthy understanding of our species' role in the greater scheme of things. A more humble view on ourselves if you will.

An abstract of the study can be found here.