Inequality in faculty placement

inequality in academia

How does your PhD institution affect your chances at a faculty position?

Across disciplines, we find steep prestige hierarchies, in which only 9 to 14% of faculty are placed at institutions more prestigious than their doctorate…Under a meritocracy, the observed placement rates would imply that faculty with doctorates from the top 10 units are inherently two to six times more productive than faculty with doctorates from the third 10 units. The magnitude of these differences makes a pure meritocracy seem implausible, suggesting the influence of nonmeritocratic factors like social status.

Academia ROCSome factoids:

  • This falloff in faculty production is sufficiently steep that only the top 18 to 36% of institutions are net producers of within-discipline faculty
  • Differences by gender are greatest for graduates of the most prestigious institutions in computer science and business, where median placement for women graduating from the top 15% of units is 12 to 18% worse than for men from the same institutions. That is, the hierarchy is slightly steeper for elite women than for elite men in these disciplines.
  • These results are broadly consistent with an academic system organized in a classic core-periphery pattern (17), in which increased prestige correlates with occupying a more central, better connected, and more influential network position…As a result, faculty at central institutions literally perceive a “small world”  as compared to faculty located in the periphery.
  • Reinforcing the association of centrality and insularity with higher prestige, we observe that 68 to 88% of faculty at the top 15% of units received their doctorate from within this group, and only 4 to 7% received their doctorate from below the top 25% of units.

You can find their prestige rankings for Computer Science, Business, and History in their supplemental material (figure S10).

Obviously, things are more complicated when you have postdocs or are in a “high status” lab in a “low prestige” university.

The problems of academic insularity and flow of good ideas is evident.

Reference

Clauset A, Arbesman S, & Larremore DB (2015). Systematic inequality and hierarchy in faculty hiring networks Science Advances

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Optimal hipster theory

I think people are trying to send me a message. For the last few days, I’ve been getting a steady stream of emails letting me know about a new paper posted on the arXiv – The hipster effect: When anticonformists all look the same (for the record, I have never had an ironic mustache.) It’s definitely because of the math involved. Yeah, that’s it.

Just as I started to write this up, though, I see that someone else has already done a fantastic job at a lay introduction to the paper:

Touboul begins by envisioning a world where people choose between just two styles: Call them punk or normcore. There are two kinds of people in this world: those who like to go with the flow, and those who do the opposite — hipsters, in other words. Over time, people perceive what the mainstream trend is, and either align themselves with it or oppose it.

Here are some examples with a population of three conformists and one hipster. How the world evolves over time depends on who starts off in the majority and who starts off in the minority. Take white to be normcore, and black to be punk (obviously).

What if this world contained equal numbers of conformists and hipsters? No matter how the population starts out, it will end up in some kind of cycle, as the conformists try to catch up to the hipsters, and the hipsters try to differentiate themselves from the conformists.

Essentially, the model assumes that individuals have two states (styles) and they flip between them. The switching rate is determined by the mean-field trend such that mainstream individuals will flip to the mainstream (mean-field) style at a high rate; hipsters will flip at a much lower rate. This can be modeled as a spin-glass system where many analytical results are already known.

Now, spin-glass systems are known from magnetism: they help describe how whole systems can suddenly switch from one macro state to another. For instance, from disorder to sudden order. In the hipster system, near the critical point you get sudden transient alignments of hipsters before switching randomly:

hipster critical point

A lot of flop flop flopping from the nonconformists (hipsters).

A more interesting result is that a time-delay induces a Hopf bifurcation in the system causing systematic hipster alignment:

hipster hopf bifurcations

This immediately suggests that decreased time delays should reduce the coherence of anticonformist trends. Luckily we have a natural experiment – the Internet. I’m not aware enough of fashion to comment on that but I am a pretty big music junky. Thanks to the internet, music genres have split into subgenres which split into microgenres and oh god it’s so hard to even keep track of what is what any more.

Similarly, the paper shows that if you there is a spatial extent to the model, then at low delays you only get hipster synchronization when the spatial extent is not too large or too small (in the figure below, the x-axis a is spatial extent, y-axis tau_0 is temporal delay).

hipster time and area delays

Despite the simplifications in the model – fashion is one-dimensional and everyone exists at unit distance etc – there is insight to be gained.

Additionally, while hipster-hunting is an Internet past-time, distinctiveness is a serious matter in ecology and sociology. This is useful!

Reference

Jonathan Touboul (2014). The hipster effect: When anticonformists all look the same arXiv arXiv: 1410.8001v1

Testosterone! Aggression!

Could low testosterone be what made us modern humans?!

The hormone, associated with both biologically male characteristics and aggression, makes skulls grow those heavy brows we associate with our evolutionary ancestors…The key, the researchers claim, could be found in the feminized skulls that became more prevalent around that time. A rounder face in humans isassociated with less testosterone, and less testosterone can mean better cooperation between individuals. Less head clubbing and more community building, basically.

The paper is pretty heavy on speculation – human skulls have gotten less masculinized over time, though obviously that could be for reasons beyond changing levels of testosterone; something downstream or different altogether could be the cause. But I think this is a good time to review some things about testosterone. From Sapolsky’s The Trouble With Testosterone:

Okay, suppose you note a correlation between levels of aggression and levels of testosterone among these normal males. This could be because (a) testosterone elevates aggression; (b) aggression elevates testosterone secretion; (c) neither causes the other. There’s a huge bias to assume option a, while b is the answer. Study after study has shown that when you examine testosterone levels when males are first placed together in the social group, testosterone levels predict nothing about who is going to be aggressive. The subsequent behavioral differences drive the hormonal changes, rather than the other way around…

Yes, it’s going to be on the final, and it’s one of the more subtle points in endocrinology—what is referred to as a hormone having a “permissive effect.” Remove someone’s testes and, as noted, the frequency of aggressive behavior is likely to plummet. Reinstate precastration levels of testosterone by injecting that hormone, and precastration levels of aggression typically return. Fair enough. Now this time, castrate an individual and restore testosterone levels to only 20 percent of normal and . . . amazingly, normal precastration levels of aggression come back. Castrate and now generate twice the testosterone levels from before castration—and the same level of aggressive behavior returns. You need some testosterone around for normal aggressive behavior—zero levels after castration, and down it usually goes; quadruple it (the sort of range generated in weight lifters abusing anabolic steroids), and aggression typically increases. But anywhere from roughly 20 percent of normal to twice normal and it’s all the same; the brain can’t distinguish among this wide range of basically normal values…

Round up some male monkeys…number 3, for example, can pass his day throwing around his weight with numbers 4 and 5, ripping off their monkey chow, forcing them to relinquish the best spots to sit in, but, at the same time, remembering to deal with numbers 1 and 2 with shit-eating obsequiousness…Take that third monkey and inject him with testosterone.  Inject a ton of it in him…And no surprise, when you check the behavioral data, it turns out that he will probably be participating in more aggressive actions than before…Is he now raining aggressive terror on any and all in the group, frothing in an androgenic glaze of indiscriminate violence?  Not at all.  He’s still judiciously kowtowing to numbers 1 and 2 but has become a total bastard to numbers 4 and 5. This is critical: testosterone isn’t causing aggression, it’s exaggerating the aggression that’s already there.

And don’t forget that the “effect of testosterone” can be culturally contingent:

However, subjects who believed that they received testosterone—regardless of whether they actually received it or not—behaved much more unfairly than those who believed that they were treated with placebo. Thus, the folk hypothesis seems to generate a strong negative association between subjects’ beliefs and the fairness of their offers, even though testosterone administration actually causes a substantial increase in the frequency of fair bargaining offers in our experiment.

And, revisiting this somewhat-embarrassing early post of mine about the role of testosterone in social domination (and physical displays associated with it):

However, if you go ahead and stick a needle in the other birds – the ones that didn’t get the testosterone injection – they also had an increase in testosterone level.  In fact, they had the same level of testosterone in their bloodstream as those with the injection.  But these birds had smaller combs [dominance displays]! …So testosterone levels per se don’t mediate dominance.  It’s also not at all clear whether testosterone is needed for aggression…Dark-eyed juncos will defend their territory by squawking at unwanted intruders…But at least for [some] behaviors, testosterone surges aren’t associated with aggressive social behavior.

Why the new paper by Christakis and Fowler on friendship makes me queasy

I am a neuroscientist, and as a neuroscientist I have a strange belief that most of who we are comes from our brains. My entire career is based around understanding the neural basis of behavior which, I think, is pretty justifiable.

So when I see paper looking at the genetics of behavior, I expect to see at least one or two genes that are directly involved in neural function. A dopamine receptor, probably, or maybe some calcium channels that are acting up. And in one recent paper looking at schizophrenia, that’s exactly what we find! A D2-like dopamine receptor and some glutamate genes. My world is consistent.

But then we get a paper about friendship from Christakis and Fowler who find that friends are more likely to be genetically related to you than chance. So that means that your close friend? Basically a fourth cousin. What Christakis and Fowler have found is a few sets of genes that seem like they might influence friendship. The most important is an olfactory gene which just reeks of pheromones (or possibly hygiene). But the next most important genes? They have to do with linoleic metabolism and immune processes!

Now what am I, as a neuroscientist, supposed to do with that? How do I reconcile my neural view of the world with one where metabolic processes are influencing decisions?

Perhaps I can quiet my mind a little. In a past blog post, I wrote about how social status causes changes in genes related to immune processes. So maybe I can squint and say that okay, really this is an epiphenomenon relating to social status.

But if I’m going to understand behavior – what do I have to know? Do I have to understand literally all of biology? That traits and choices are being affected by what seem to be totally non-brain factors? That my philosophical position of the extended mind is maybe true? That makes me a little queasy.

(End massively speculative rant.)

References

Christakis NA, & Fowler JH (2014). Friendship and natural selection. Proceedings of the National Academy of Sciences of the United States of America, 111 (Supplement 3), 10796-10801 PMID: 25024208

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The lives of sociable spiders

Some spiders are pretty social:

But about 25 arachnid species have swapped the hermit’s hair shirt for a more sociable and cooperative strategy, in which dozens or hundreds of spiders pool their powers to exploit resources that would elude a solo player…In laboratory experiments, the researchers showed that spiders exposed to the same group day after day developed stronger and more distinctive personalities than those that were shifted from one set of spiders to the next. Moreover, the spiders in a stable social setting grew ever less like one another over time.

In other words, far from fostering behavioral conformity, a predictable social life accentuated each spider’s quirks and personal style, rather as the characters in a sitcom — the Goth girl, the huckster, the lovable buffoon — rise ever more to type with every passing laugh-tracked week.

Equally dramatic was the impact of social conditions on the boldness test. Stable spider groups, composed of six spiders that remained together for up to four weeks, showed the greatest variety between individuals, the greatest mix of bold and shy, as well as the highest individual consistency: The pebble-playing times of the boldies grew shorter while those of the timids lengthened. Among shifting spider groups, by contrast, the boldness scores proved far less predictable, as though the spiders didn’t quite know what was expected of them.

I’ve covered some social aspects of spiders before, though have a more complicated social life. The idea that personality evolves through reinforcing already-existing traits has also been explored a little before.

Antibiotics, social status and fat

In the New York Times yesterday, Pagan Kennedy reminds us of the link between antibiotics and weight gain:

IF you walk into a farm-supply store today, you’re likely to find a bag of antibiotic powder that claims to boost the growth of poultry and livestock. That’s because decades of agricultural research has shown that antibiotics seem to flip a switch in young animals’ bodies, helping them pack on pounds. Manufacturers brag about the miraculous effects of feeding antibiotics to chicks and nursing calves. Dusty agricultural journals attest to the ways in which the drugs can act like a kind of superfood to produce cheap meat.

But what if that meat is us?

Researchers also tried this out in a study of Navy recruits…The Navy men who took a dose of antibiotics every morning for seven weeks gained more weight, on average, than the control group.

A study in mice last year found the same thing: when fed a stream of antibiotics, they slowly fattened up:

The antibiotics altered the composition of bacteria in the guts of the mice and also changed how the bacteria broke down nutrients. The bacteria in treated mice activated more genes that turn carbohydrates into short-chain fatty acids, and they turned on genes related to lipid conversion in the liver. Presumably, these shifts in molecular pathway enable fat build-up. Just as farm animals get fat, the antibiotic-fed mice put on weight.

Given that high-status individuals (well, baboons) have been shown to have enriched immune-related genes compared to low-status individuals, I wonder if social status can regulate weight gain (etc) through the composition of bacterial flora? Just a thought, and not something I know a lot about…

Friends with benefits

tl;dr: Rodents will help each other get out of trouble, though they will help each other more if they are related. Social learning in rodents can require information transmission between ACC and amygdala, and the strength of synapses in mPFC dictates social status.

He wanders into the room and stops – someone else is peering at him out of a tiny plastic cage. Wandering over he must decide: should he help him out of the cage? Or let the creepy situation remain creepy, and leave them stuck in there?

Rats, it turns out, aren’t big fans of creepy situations and will actively go out of their way to help their furry compatriots escape from their cages. Not only will they help other rats escape their cages – even if they don’t know them – but if they find a bite of chocolate they’ll hand over some of that as well. [Though if you look at the data: the little bastards wait half a week before they get around to doing it.]

Screen shot 2014-02-08 at 11.27.27 AM

That’s fine but things can get a bit sinister when the rats aren’t just strangers but strangers that appear different. When they find another rat trapped in a cage that is of a different strain, the free rats would rarely attempt to let the trapped rats loose. This isn’t purely a matter of rats being different from one another, but rather of rat-features that they weren’t familiar with. When rats were housed with rats of different strains, they would help other rats of that strain out. Individuals of that outgroup had been ‘humanized’, so to speak. Yet, own-group preference wasn’t innate – if they weren’t housed with other rats of their own strain, they wouldn’t help them, either. For an example, watch this movie from the paper (which I can’t directly embed).

We already know a bit about the neuroscience of empathy and social structure in rodents. A mouse that observes a fellow mouse receiving painful shocks in a certain area of their cage will learn to avoid that area through pure social observation. However, they learn better when it is a sibling that is being shocked than when it is an unrelated rat. This learning requires a region of the brain known as the anterior cingulate cortex (ACC), though the region can be inactivated during later retrieval and recall without affecting the behavior. It also requires the amygdala, not just for learning but also for later retrieval and recall. During learning, the ACC and amygdala are connected by strong (theta) rhythms, potentially to transmit information between the areas.

Screen shot 2014-02-20 at 10.58.38 AMAnother factor guiding social behavior is social status. Status affects behavior on a range of levels, from how decisions are made to how healthy an individual is. It is pretty surprising to me that in rodents, social status can be directly changed by changing the strength of synapses in the medial prefrontal cortex (mPFC). I’ve only ever seen a broad neuromodulator like serotonin do something like that, though I would hesitate before suggesting that they two mechanisms were connected. On the other hand, mPFC is upstream of serotonergic areas so increased synaptic strength could mean increased serotonin!

References
Ben-Ami Bartal I, Rodgers DA, Bernardez Sarria MS, Decety J, & Mason P (2014). Pro-social behavior in rats is modulated by social experience. eLife, 3 PMID: 24424411

Ben-Ami Bartal I, Decety J, & Mason P (2011). Empathy and pro-social behavior in rats. Science (New York, N.Y.), 334 (6061), 1427-30 PMID: 22158823

Wang F, Zhu J, Zhu H, Zhang Q, Lin Z, & Hu H (2011). Bidirectional control of social hierarchy by synaptic efficacy in medial prefrontal cortex. Science (New York, N.Y.), 334 (6056), 693-7 PMID: 21960531

Jeon D, Kim S, Chetana M, Jo D, Ruley HE, Lin SY, Rabah D, Kinet JP, & Shin HS (2010). Observational fear learning involves affective pain system and Cav1.2 Ca2+ channels in ACC. Nature neuroscience, 13 (4), 482-8 PMID: 20190743

Economics of Social Status

In economic terms, for a good to function as money it must serve three related purposes:

  1. A medium of exchange,
  2. A store of value, and
  3. A unit of account.

We’ve already discussed how status functions as a medium of exchange. Because it’s so fluid, it can be used to price favors and other goods at relatively fine resolutions, and it facilitates transactions that wouldn’t otherwise be able to occur. Negotiating with status beats the hell out of bartering — i.e., trading one specific good for another — thereby allowing smoother, more efficient economies to develop.

Certain goods – money, nice cars – are only useful insofar as they contribute to first-order goods: food, water, reproduction.  Does social status count as a first- or second- order good?  While it doesn’t keep us alive, we are social creatures that crave and need social attention.  Consider what happens to socially isolated individuals, especially those in prison.  Go read about the economics of social status.

Old bees get a new lease on life (through glutamate!)

Have you ever heard a story about an elderly person who seems surprisingly fine and with it in the outside world, but is then transferred to a nursing home where they quickly slide from their mental peak?  Have you ever stayed at home all day, playing video games (ahem) and feeling a bit sluggish only to go back to mentally stimulating work and feel more alert?  No matter what people say, our work is our life.

Honeybees spend the first two or three weeks of their life as nurses, taking care of the young, tending to the queen, building out and cleaning the hive.  When they get older, they get reassigned to a job outside the hive as a forager.  Now they have to search out nectar and pollen and live in the dangerous outside world.  They are quick to die off as the stress of the outside environment and downright intense physical work causes them to age.  Not only are there physical effects, but mental ones, too: their ability to learn and associate is impaired.

But not all is lost for these bees!  Sometimes disaster falls a hive and more nurses are needed.  When this happens, some forager bees return to become nurses.  Baker et al studied these bees to see how returning to the hive affected them.  Although in some ways the returned bees looked like their foraging compatriots, in terms of learning and memory they were identical to their younger nursing brethren.  They had a new lease on life!

Some of these returned nurses did better than others.  Baker et al looked at what proteins were differentially expressed between these two groups, and the data pointed to proteins that affected physical structure (alpha-tubulins), stress and cell maintenance, and neuronal functioning and signaling.  One of the most abundantly different proteins was the glutamate transporter homologous to EAAT2.  Glutamate is the primary neurotransmitter in the brain, and is the basis for the most common form of long-term learning.  The glutamate transporter will remove glutamate from the extracellular space, so different amounts of glutamate transporter will change the concentration.  This means that cells will be generally more or less excitable and will have different levels of plasticity.

There are clearly a couple of problems with this study which can basically be labeled statistics.  Do the bees learn better because they have returned to nursing?  Or do they return to nursing because they are the better bees?  This is selection bias.  Also, if the bees are learning better, is it because of this change in proteins?  Or were those differences in proteins there before they returned, and something totally different has changed?

What the paper may provide evidence for, though, is the social brain hypothesis.  This hypothesis suggests that the reasons humans got smarter is because we lived in social groups, and the fittest individual was the one that was smartest at dealing with the social group.  Perhaps the bees that return need to be the smartest because they have to return and deal with a social environment, a possibly more intellectually demanding environment.  These bees have more to keep track of, a variety of other bees to placate.  Not only does your job affect you, but so does your social environment.

Well, it’s something to think about at least.

References

Baker et al (2012). Age-related learning deficits can be reversible in honeybees Apis mellifera
Experimental Gerontology DOI: 10.1016/j.exger.2012.05.011

Photo from

How social status determines your health

You wouldn’t think how people perceive you could directly affect your health, would you?  Luckily, science is here to save the day and to tell you, you’re wrong.  A pair of papers published in PNAS in the last month have investigated the interaction between social status and health, and the findings compliment each other rather nicely.

The authors of the first paper tracked baboons over thirty years and made a compelling figure (show at right) showing that low-ranking males are sick more often, and for longer, than high-ranking males.  It has been theorized that the biological effects of high social status – testosterone, high glucocorticoids, high reproductive effort – would reduce health.  After all, if these high-ranking male baboons have to spend all their time and energy making sweet monkey love, there wouldn’t be much energy left over for healing, would there?  However, they found no evidence for this.  In fact, alpha males seemed to heal faster than anyone else.

The authors of the other paper examined the different genes that are regulated in low- and high-status female rhesus monkeys.  The previous paper tracked male animals in the wild, and this one kept female animals in the laboratory.  The authors took blood samples from the monkeys to profile gene expression – though only after dominance order had been established.  It would have been great had they done so before hand to see if there were genes predictive of social status, or if expression changed in any appreciable way.  But no matter.  By using a PCA analysis – basically, finding the combinations of genes that most explained the variance in the behavior – they found that the first principle component was predictive of social status.  This tells us that gene expression is intertwined with your social status.

Almost 1000 genes were found to be associated with rank, 535 of which were more enriched in high-ranking individuals and 452 of which were more enriched in low-ranking individuals.  So a lot is going on in there and getting changed!  Consistent with the previous paper, there was the largest cluster of enriched genes were immune-related.  This included interleukin signaling, T-cell activation, and chemokine/cytokine inflammation.  Perhaps, then, the reason high-ranking males heal faster is because the right immune-related genes were enriched.  But that leaves the question, why should that be so?

The paper included an excel spreadsheet of the enriched genes which can be a bit fun to scroll through; following on something I touched on in the previous post, I expected to find dopamine receptor genes enriched in one of the conditions but I didn’t.  Something to keep in mind.

I guess the moral of story here is: socializing is dangerous.  Or maybe not socializing is dangerous.  Either way, watch out!

References

Archie, E., Altmann, J., & Alberts, S. (2012). Social status predicts wound healing in wild baboons Proceedings of the National Academy of Sciences, 109 (23), 9017-9022 DOI: 10.1073/pnas.1206391109

Tung J, Barreiro LB, Johnson ZP, Hansen KD, Michopoulos V, Toufexis D, Michelini K, Wilson ME, & Gilad Y (2012). Social environment is associated with gene regulatory variation in the rhesus macaque immune system. Proceedings of the National Academy of Sciences of the United States of America, 109 (17), 6490-5 PMID: 22493251