Testing magical misdirection

Variations of the ‘cups and balls’ magic trick have been performed for over two thousand years. One simple version involves three inverted cups into which the performer loads brightly covered balls. Using sleight of hand, the balls are moved in and out of the cups. Magicians hold many beliefs about why this trick is so effective, one of which is that it’s critical for the performer to mislead the audience with his direction of gaze. Hector Rieiro, Susana Martinez-Conde and Stephen Macknik of the Barrow Neurological Institute got the assistance of Teller (of the famed magical duo ‘Penn & Teller’) to test this. Even when Teller performs this trick with clear cups he can still surprise an audience.

Seven subjects snuggled their chins onto mounts and watched film clips of Teller performing different variations of cups and balls while eye tracking devices monitored their gazes. They were asked to immediately press one button as soon as a ball made physical contact with either a cup or the table and a second button as soon as a ball stopped touching a cup or the table. The volunteers consistently reported seeing the balls’ movements some time after the actual movements. For example, people thought a ball was placed in a cup after it had actually been placed there.

Interestingly, covering Teller’s face so that he couldn’t use his own gaze to misdirect the viewers did not improve their performance. This is contrary to most magicians’ intuition on the matter. Using gravity to assist in the trick did not increase misdirection either, also a common magical misconception.

Compare two versions of the trick, a standard one, in which all three cups are treated the same way, and one in which Teller lifts up the third ball. More people were fooled by the latter. How about you?


Rieiro, H., Martinez-Conde, S., & Macknik, S. (2013). Perceptual elements in Penn & Teller’s “Cups and Balls” magic trick PeerJ, 1 DOI: 10.7717/peerj.19.

Just for fun: Stress-free parking

This Wöhr Multiparker 730 was developed a few years ago. So why don't they have this at my local mall yet?

The effectiveness of background checks for gun sales

There’s been some debate lately about what to do about gun violence in the United States. A vast majority of citizens on the left and the right are in favor of universal background checks (asking about prior felonies and mental illness) for all gun purchasers. But would such a measure be effective? According to a new study by Garen Wintemute of the University of California, Davis, it would be.

Wintemute based his analysis on currently existing laws and conditions. To begin with, he differentiates between licensed dealers and private sellers. The former must collect information from their customers before selling them weapons and then keep permanent records on each sale. Private sellers have no such federal requirement, although some states do require background checks for private party sales. There is no limit as to how many guns a person can sell before being legally considered a dealer rather than a private seller.

In many estimates, 40% of gun sales do not involve licensed dealers and thus may not involve background checks. That number increases to over 90% for ‘prohibited’ people who would not pass a background check (presumably the sort of people we’d prefer to keep guns away from) and to virtually 100% for juveniles seeking to buy weapons.

Wintemute then compared gun sales in California, where even private sellers must do background checks on their customers, and four states with no such restrictions (Arizona, Nevada, Texas and Florida). In California gun shows, even private party sales are conducted through licensed transfer agents. Sales in the other states can be, and usually are, directly between seller and buyer. There were two consequences of this. First, the gun shows across the California border in Nevada were full of California buyers (over 30% by license plate count). Second, there were six times as many illegal gun purchases (buying a gun for someone else who could not pass a background check) in the neighboring states as in California.

These data strongly suggest that federally mandated universal background checks and record keeping would prevent many questionable people from purchasing firearms. People who could not pass a check in California would not have the option of going to Nevada to get their weaponry. This would be particularly helpful in cities like Chicago, which have strict gun regulations but which get a huge influx of weapons from just outside the city limits.

No one is suggesting that universal background checks would solve all our problems. They would however, undoubtedly reduce the number of guns available to people who should not be trusted with guns, especially people with violent or unstable histories. It’s no wonder that over 90% of Americans now favor enacting laws requiring such measures.

For more details, watch Wintemute explain his findings below.



Update 4/2013: Mayors Against Illegal Guns has a fact sheet on background checks.

Redefining the habitable zone

Although finding exoplanets is interesting (and nearly a thousand have been confirmed to date), the really exciting news would be to find another planet capable of sustaining life. To do so, such a planet would almost certainly orbit within a certain radius from its star: the ‘habitable zone’ (HZ). The trouble is, astronomers aren’t entirely sure just what the boundaries of a star’s HZ are. Just recently, a team of Pennsylvania State University cosmologists, led by Ravi Kopparapu, have redefined the borders of the HZ.

The region within an HZ is largely determined by the presence of two molecules: liquid water and carbon dioxide. If a planet is too close to its star, any water will boil off into space. Too far, and the water will remain permanently frozen. Because the outer edge of the HZ can be extended if the planet has a carbon dioxide atmosphere to warm it, researchers take the presence of CO₂ into account when predicting the outermost limits of an HZ.

While Kopparapu and his colleagues still use H₂0 and CO₂ to define where an HZ will fall, they believe that the criteria used to detect those molecules needs to be adjusted. When they used updated data, they found that HZs tend to be a bit further out than previously thought. This means that some planets that were written off may in fact be within the HZ of their star, but also that some hopeful candidates aren’t in the HZ after all.

Caption: The graphic shows habitable zone distances around various types of stars. Some of the known extrasolar planets that are considered to be in the habitable zone of their stars are also shown. On this scale, Earth-Sun distance is one astronomical unit, which is roughly 150 million kilometers.

Credit: Chester Herman

Notice that, according to the new standards, Earth (seen near the top right) barely falls into the HZ of our sun. No doubt this new model has some more tweaking in store.

Ravi kumar Kopparapu, Ramses Ramirez, James F. Kasting, Vincent Eymet, Tyler D. Robinson, Suvrath Mahadevan, Ryan C. Terrien, Shawn Domagal-Goldman, Victoria Meadows, & Rohit Deshpande (2013). Habitable Zones Around Main-Sequence Stars: New Estimates Astrophysical Journal : arXiv:1301.6674.

Moles smell in stereo

We humans are well aware that our two eyes and ears gather slightly different inputs that are combined into ‘stereo’ vision or hearing. We also have two nostrils, close together as they are. Can we also smell in stereo? If we’re like moles, we can.

Kenneth Catania of Vanderbilt University used blind eastern American moles (Scalopus aquaticus) as his models. Although these moles have eyes, their eyelids are fused shut, a reasonable adaptation for an animal that spends its days swimming through dirt. Instead, the animal navigates its subterranean home by using its nose.

Catania placed each mole in a special testing chamber. Upon entering the chamber, the mole was presented with a semicircle of 15 wells, only one of which contained a tasty tidbit (a segment of earthworm). The moles were videotaped and monitored to detect sniffing behavior. In some trials, one of the nostrils was blocked.

With both nostrils clear, the moles were 100% accurate in bearing straight for the food-containing well. However, with a nostril blocked, they first headed for one of the empty wells 70% of the time. More specifically, the moles were drifting toward the open nostril. That is, when their left nostrils were blocked, they veered right and vice versa. In all cases, the moles eventually found the food.

In a final set of experiments, tubes were inserted into the moles nostrils such that airflow direction could be switched. When these tubes were crossed, scent would flow into the left nostril from the right side of the head and vice versa. This completely confused the moles and them to miss the food entirely. You can see some of these experiments below. Keep in mind that these creatures are blind and are literally following their noses.

Taken together, these data indicate that the moles are using their two nostrils to gather separate clues about the location of their prey. If this were not the case, the moles should have followed the same path toward the food regardless of whether they were using one nostril or two (though perhaps a bit more slowly with only one nostril). They aren’t merely getting less input with only one nostril, they’re also losing directional information. This is no different than the change we experience if one of our eyes or ears is blocked.  

So does this finding apply to all mammals? That has yet to be seen, though it’s certainly possible. Moles were a good model for this study because their prey search isn’t confounded by visual clues as it would have been if Catania had used dogs or rats. If humans have this ability we probably don’t notice it as we rely so little on smell for orientation.


Catania, K. (2013). Stereo and serial sniffing guide navigation to an odour source in a mammal Nature Communications, 4 DOI: 10.1038/ncomms2444.

The truth about genetic engineering

Because genetic engineering is so often misunderstood, I'd like to explain what it is. Genetic engineering is simply a catch-all phrase for cultivation techniques that involve direct manipulation of genes. You can add a gene to an organism that didn’t previously have that gene or you can remove or alter an existing gene. Either way, you’re limited to genetic changes that will be viable in the resulting organism just as you would be by crossbreeding.

The following diagram compares conventional breeding to genetic engineering (transgenesis or cisgenesis). By the way, a ‘cultivar’ is a currently available version of the crop, and a ‘plasmid’ is a small circle of DNA that functions as a vehicle for transferring your gene of interest. Note that you have much less control over what gets added to the genome with conventional breeding. Also, ‘many backcrosses’ could mean hundreds of generations.

This brings me to some important points. The fact that the genes have been manipulated doesn’t automatically make the result toxic. It depends on which genes have been added or altered. If you add beta-carotene genes to rice, you get a crop that could potentially save hundreds of thousands of children from dying or going blind from vitamin A deficiency. 

Sometimes, genetic engineering even brings unexpected benefits. For example, John Haegele and Frederick Below from the University of Illinois found that Bt corn has much higher yields than conventional corn. Bt corn is corn that is genetically engineered to contain a gene from a soil bacterium named Bacillus thuringiensis (hence the ‘Bt’). The gene in question encodes a protein that is toxic when ingested by a specific type of insect pest. It is not toxic to other kinds of insects such as bees or beetles, and certainly not to humans or other vertebrates. Bt corn does, however, have far less predation from rootworms and consequently, the plants have a much healthier root system. This, in turn, allows the plants to take up nitrogen more efficiently, resulting in higher yields with less added fertilizer.

This is good news because genetic engineering is here to stay. As more and more genomes are being sequenced, it’s ridiculous to expect crop scientists to cross breed generation after generation hoping to get a desired trait when they can just add the gene they’re interested in. Perhaps more importantly, genetic engineering is increasingly being used in medicine. It’s used to develop strains of mice or other organisms that mimic human diseases, and to produce products such as insulin and human growth hormone. Obviously, I’m simplifying the work involved, but you get the idea. As a technique, genetic engineering is far too useful to give up.

Of course, there’s the possibility of purposefully or inadvertently adding harmful genes. But those are problems of misuse, not with the protocol itself. While there will undoubtedly be unanticipated problems, these problems can and should be managed responsibly. And just to be clear, ethical issues involving patents or business practices are not an indictment of the methodology behind genetic engineering. 

Just for fun: Meteors

On February 15th, a large meteor fell near the Russian city of Chelyabinsk, which is located just east of the Ural Mountains. Although spectacular, it did cause a fair amount of damage, including over a thousand injuries and many broken windows.

Here's a compilation video of the meteor including some of the aftermath:



More on this at Bad Astronomy and at The Guardian.

Meanwhile, that same day another meteor was seen near San Francisco:



Luckily, this one didn't cause any damage.

Remember, this was also the same day that the asteroid 2012 DA14 did its close fly-by. 



Quite a day for sky-watchers.

Insect driven robot

Male silk moths are highly attuned to the odor of female silk moths. When a male detects this odor, he begins a characteristic ‘dance’ designed to bring him into proximity with his paramour. During the first phase of the dance, he walks in a straight line. You can get the moth to forego the subsequent parts of the ritual (zig-zags and circles) by giving him another whiff of pheromone. In that case, he’ll surge straight forward for each puff of odor he detects. I think you can see where this is going. You can get a male silk moth to follow a straight path by giving him a series of puffs of female silk moth pheromone. Even better, you can get the moth to steer a robot for you.

Noriyasu Ando and his colleagues from the University of Tokyo, attached a male adult silk worm to a free-floating polystyrene ball. You can see the result below.

In both panels, puffs of pheromone directs the moth to steer its track-ball controlled vehicle toward the source of the odor. In the right-hand panel, the researchers have messed with the robot steering, making it continuously veer to one side. In other experiments, the front of the tiny car is covered, blinding the driver. Regardless of what the researchers threw at it, the moth was able to steer toward the pheromone over 80% of the time.

I’m pretty sure that the impetus for this research was not to help physically handicapped silk moths find a partner. Rather, the scientists hope to adopt the insect’s odor tracking ability in driverless robots.



Ando, N., Emoto, S., & Kanzaki, R. (2013). Odour-tracking capability of a silkmoth driving a mobile robot with turning bias and time delay Bioinspiration & Biomimetics, 8 (1) DOI: 10.1088/1748-3182/8/1/016008.

Time to bring back H. pylori?

You may have heard of the bacteria called Helicobacter pylori. They are responsible for many of our gastric woes, such as ulcers and some types of cancers. That being the case, you may think it’s a good thing that the microbes are being eradicated in developed nations. Not so fast. H. pylori actually has a mixed record where human health is concerned. Yes, it does cause ulcers, but on the other hand, there is some evidence that H. pylori colonization protects against asthma and allergies. Even more intriguingly, the bacteria may also protect against obesity.

Electron micrograph of H. pylori possessing multiple flagella

H. pylori secrete chemicals that in turn affect the production of a variety of hormones manufactured by the gut epithelial cells. For example, when the bacteria are present, ghrelin plasma levels go way down. Once H. pylori are eradicated, ghrelin levels rise.  And what does ghrelin do? Stimulate the appetite. H. pylori are also associated with higher concentrations of the hormone leptin, which is responsible for the feelings of satiety. So, is it a coincidence that developed nations have both a low incidence of H. pylori infection and a high incidence of obesity? Josep Bassaganya-Riera of Virginia Tech and his colleagues don’t think so.

The researchers used a couple of mouse models for their studies. One strain of mouse was deficient in leptin receptors and the other were normal mice that were fed a high-fat diet. Either way, the mice were expected to quickly become obese during the course of the experiments. However, H. pylori infection had a number of effects on them.

Mice that were fed the high fat diet had four times more leptin after being infected with H. pylori. Remember, this is a hormone that tells us it’s time to stop eating. Fasting blood glucose levels were significantly lower in infected mice of both types and returned to normal more quickly following a glucose challenge. In addition, infected mice had less white adipose tissue, a.k.a. fat. Finally, H. pylori carriers has less insulin resistance than their uninfected cohorts. This suggests that H. pylori may play a role in helping its hosts maintain a healthy weight.

So, if you’ve been battling weight gain, should you have yourself infected with H. pylori? That may not be the best idea right now. First, there’s some chance you’re already a carrier. It’s estimated that 80% of carriers are asymptomatic. Second, H. pylori infection does have its downsides, not the least of which is an increased risk of duodenal and/or stomach cancer. However, it may one day be possible to disassociate the pathogenic properties of H. pylori from its metabolic effects. If that happens, we may all be getting dosed with H. pylori. 


Bassaganya-Riera, J., Dominguez-Bello, M., Kronsteiner, B., Carbo, A., Lu, P., Viladomiu, M., Pedragosa, M., Zhang, X., Sobral, B., Mane, S., Mohapatra, S., Horne, W., Guri, A., Groeschl, M., Lopez-Velasco, G., & Hontecillas, R. (2012). Helicobacter pylori Colonization Ameliorates Glucose Homeostasis in Mice through a PPAR γ-Dependent Mechanism PLoS ONE, 7 (11) DOI: 10.1371/journal.pone.0050069.

A swing and a miss by an asteroid

Update 2/15/13: To see a meteor passing overhead, check out next week's edition of 'Just for fun'. 

Today, a 50-meter across asteroid dubbed 2012 DA14 is not going to hit us. It will, however, come pretty darn close, as you can see from the graphic below.

Image credit: NASA/JPL

At closest approach, occurring at 19:26 UTC (the updated time standard roughly synonymous with Greenwich Mean Time), the asteroid will be about 17,000 miles from the surface of the Earth. As you can see, that’s way inside the moon’s orbit, and even within the orbit of satellites. Unfortunately, it’ll be too dim to see with the naked eye.

Here’s more about it from the folks at NASA.

You can learn lots more about it, including what would happen if it did hit us, from Phil Plait at Bad Astronomy.

MicroRNA profiles in breast cancer

In order to successfully treat cancer, it’s critical to identify the exact type of tumor afflicting the patient. This is not only important for providing the correct treatment, but also for avoiding wasting patients’ time with inappropriate treatments. Case in point: triple negative breast cancer (TNBC).

Breast cancers are classified in part by the type of receptors they express. TNBC tumors do not express any of the three most common receptors: estrogen, progesterone or Her2. Not only do TNBCs not respond to the types of treatment that non-TNBC tumors do, but there are many TNBC subgroups that each require a different protocol. Clearly, the sooner TNBCs can be identified and categorized, the better.

Kay Huebner from the Ohio State University and her colleagues have found a way to distinguish TNBCs that relies on the pattern of microRNAs (miRNAs) produced. These are tiny snippets of RNA, no more than 25 nucleotides long, that affect gene expression by binding to messenger RNA is specific places. Because TNBCs are, by definition, deficient in receptor expression, the researchers thought that there could be specific miRNAs targeting those gene sequences. This is exactly what they found.

When the scientists compared miRNAs in TNBC tumor cells versus non-tumor cells from the same women, there were about a dozen of these nucleotide fragments that were altered. In some cases the tumor cells had more of the particular miRNA, in others less of it.

The researchers also determined the miRNA profile of metastatic tumors found in the lymph nodes of the same women. Presumably, these tumors were derived from the original TNBC tumor within the breast tissue. Nevertheless there were a few differences in the miRNA profile between the lymph lesions and the TNBC or normal tissues. This may lead to insights into the metastasis process.

Overall, the scientists were able to develop two miRNA ‘signatures’ or patterns of upregulated and downregulated miRNA. Patients with one combination of miRNAs had far better long-term outcomes than those with the second, riskier pattern. The authors suggest that doctors consider more aggressive therapies for such patients.

Cascione, L., Gasparini, P., Lovat, F., Carasi, S., Pulvirenti, A., Ferro, A., Alder, H., He, G., Vecchione, A., Croce, C., Shapiro, C., & Huebner, K. (2013). Integrated MicroRNA and mRNA Signatures Associated with Survival in Triple Negative Breast Cancer PLoS ONE, 8 (2) DOI: 10.1371/journal.pone.0055910.

Just for fun: Olympus Bioscapes 2012

It's time again to see the winners of the Bioscapes Competition sponsored by Olympus America. Prizes are given for the most beautiful and/or extraordinary microscopic images, which can be either still or videos. The winning entries must "depict subjects that are, or at one time were, living". You can peruse the winners' gallery here. 

Below is the grand prize winner, an absolutely mesmerizing video of rotifers, taken by Australian Ralph Grimm.

Misfolded proteins lead to heart disease

Proper protein folding is critical for cell functioning. Lately, there’s been news that protein misfolding may be implicated in a range of neurodegenerative diseases such as Parkinson’s, Huntington’s and Alzheimer’s. Monte Willis and Cam Patterson of the University of North Carolina, Chapel Hill, review the case that heart disease should be added to the list.

There’s no doubt that the cardiomyocytes (heart cells) that give the heart its contractile power live in a delicate balance of protein formation and destruction. In a healthy heart, proteins are constantly being turned over with new proteins being made and old or damaged proteins degraded and removed from the cell. Misfolded proteins can be particularly problematic.

One problem is that misfolded proteins can assemble into larger clumps that disrupt cell functions. And in fact, a variety of cardiac stress disorders are associated with these protein masses. You can induce mouse heart cells to accumulate aggregates of misfolded proteins by stressing them in varying ways and you can observe these accumulations in the damaged hearts of human patients.

These and other lines of evidence suggest that protein folding is critical for proper cardiac functioning. It also means that researchers would do well to focus on preventing protein misfolding as a way to combat heart disease. One way to do this might be to increase the number of protein chaperones (quality control proteins that ensure the proper folding and positioning of other proteins). Mice with a genetic predisposition to heart disease that had been given drugs to increase the expression of these chaperones had significantly less cardiac disease than their untreated fellows.


Willis MS, & Patterson C (2013). Proteotoxicity and cardiac dysfunction--Alzheimer's disease of the heart? The New England journal of medicine, 368 (5), 455-64 PMID: 23363499.

Waiving informed consent

The Federal Drug Administration (FDA) has strict guidelines about recruiting participants in medical studies. Subjects must be able to fully consent to the procedures being evaluated. This is all well and good, but what about procedures specifically geared to helping people who have suffered some life-threatening trauma? Such individuals are often in no condition to consent even if doctors had the time to wait for such approval before acting. Yet, without clinical trials, it’s difficult for medical professionals to learn and improve their treatment methods.

Because of this, in 1996, the FDA established an Exception from Informed Consent (EFIC) policy. If an incapacitated patient meets specific criteria (his condition is immediately life-threatening and may benefit from the proposed treatment), doctors can enroll him in a clinical trial without his or his family’s consent. Carrie Sims of the University of Pennsylvania and her colleagues wondered what people think about this.

The researchers queried 172 trauma patients and their family members just prior to discharge from a hospital about their attitudes concerning the EFIC policy. In particular, the subjects were asked whether they would have been willing to participate in trials using a blood substitute if they had suffered extreme blood loss. Well over 90% of participants, both patients and family members, agreed that general research into handling trauma was critical. The same number thought that tests of the specific blood products mentioned should be done. Two thirds of people thought it would have been acceptable to enroll a family member in such studies without anyone having given consent. That number increased to three quarters for enrolling themselves.

Clearly, people see a need for clinical research and understand that such research is especially important for treating people who are on the verge of death. On the other hand, informed consent guidelines exist for a reason, not least to prevent unethical experimentation on vulnerable people. The EIFC policy may be a way to achieve the goal of testing emergency procedures while still adhering to specific codes of conduct.


Sims CA, Isserman JA, Holena D, Sundaram LM, Tolstoy N, Greer S, Sonnad S, Pascual J, & Reilly P (2013). Exception from informed consent for emergency research: Consulting the trauma community. The journal of trauma and acute care surgery, 74 (1), 157-66 PMID: 23271091.

New and improved DNA data storage

To be clear, we’re not talking about storing DNA itself. DNA is actually surprisingly stable and, under the right conditions, can last thousands of years without degrading. No, the idea is to use DNA as a medium for storing other kinds of information. For example, Nick Goldman and his colleagues from the European Bioinformatics Institute have used DNA to store all of Shakespeare’s sonnets, a color photograph and a sound recording of Martin Luther King Junior. The authors believe that their new technique could one day solve all our data archiving needs in perpetuity.

The idea of using DNA to store information is not new. DNA has long been thought an attractive data depository because all it requires for long-term maintenance is a cool, dark environment. You can also fit an amazing amount of data in a small space. The authors estimate that all the data that’s ever been created could fit in the back of one pick-up truck. And best of all, because the nucleotides don’t change, unlike cassette tapes and DVDs, the same decoding technology should work a thousand years from now.

To use DNA for data storage, you simply manufacture DNA using the sequence of As, Ts, Gs and Cs as a code to spell out whatever you wish. To be clear, these synthetic strands of DNA will not encode any genes. That is, like magnetic tape or ink, they will not have any function other than to store or retrieve information. Unfortunately, at this time, it’s exceedingly difficult to synthesize DNA that’s much longer than a hundred bases long, barely enough for a sentence. Almost any data file would have to be broken into a huge number of pieces that would then have to be faithfully joined together. Goldman and his colleagues improved upon this both by creating a novel code and by using four-fold redundancy.

Briefly, the researchers took the information to be DNA-itized (a sonnet in the example below) and converted it first into binary code (shown blue below) and then into a novel trinary code (0s, 1s and 2s, shown in red) where each digit is represented by two nucleotides. The resulting sequence of DNA (green) was synthesized in short overlapping fragments, so that each data point was found in four distinct pieces. Each fragment of DNA contained tags indicating where to fit it in order to regenerate the original sequence. The high degree of redundancy ensured accurate retrieval. 



Nature PMID: 23354052.

The scientists were able to send their DNA from the U.S. to Germany, where it was correctly reconstructed and decoded.

As of now, even this new method of DNA storage is far too expensive and has too slow a retrieval rate to be of any practical use. The authors have every expectation that this will change. Perhaps in as little as ten years, DNA will be the medium of choice for our data storage needs.

You can read more about this exciting research here.


Goldman N, Bertone P, Chen S, Dessimoz C, Leproust EM, Sipos B, & Birney E (2013). Towards practical, high-capacity, low-maintenance information storage in synthesized DNA. Nature PMID: 23354052.

The most successful college students form social networks

While almost everyone today is connected to other people via the internet, some people make far greater use of these tools than others. Luis Vaquero of Hewlett-Packard Laboratories, Bristol and Manuel Cebrian of the University of California at San Diego and NICTA, Melbourne were interested in how college students interact with one another online and how this affects their success in school. To that end, they studied how much students communicated with one another and under what circumstances. I doubt you’ll be surprised to hear that the best students formed the most complex social networks.

All in all, the researchers followed 290 students through some 80,000 interactions. You can see a sample classroom below.



Scientific Reports, 3 DOI: 10.1038/srep01174.

The squares each represent one of the 82 students in the class, and the lines represent the interactions between those students. The most persistent interactions are shown as thick blue lines and more transient interactions as dotted grey lines. The highest performing students are represented as dark blue, mid-performers as red and low-performers as green squares.

As you can see, there is a strong correlation between the number and persistence of interactions with fellow students and success in the classroom. The highest performing students formed the most persistent interactions with each other. While low-performing students would initiate contact with mid or high-performers, those students often did not reciprocate. In addition, although all students make some attempt at contact with their cohorts during the first few weeks of each semester, low-performing students quickly stopped interacting with their peers. In contrast, the high and mid performers peek in interactions by week four and maintain a high level of contact for the rest of the semester.

The authors are quick to point out that the students were not trying to be exclusionary. It’s just that the best students tend to identify one another rather quickly at the beginning of each course and find that it’s to their mutual benefit to maintain contact. Vaquero and Cebrian refer to this collaborative relationship as a ‘rich-club’ and suggest that college students who want to do well try to get into one. 


Vaquero, L., & Cebrian, M. (2013). The rich club phenomenon in the classroom Scientific Reports, 3 DOI: 10.1038/srep01174.