Author: Cathleen O'Grady

The persistent suggestion that video gaming leads to violent behavior prompts innumerable eye-rolls and Internet rants from gamers. But it’s persistent because it’s surprisingly hard to nail down a solid answer to the question. A lot of the research just raises more questions, so consensus remains elusive, despite claims to the contrary.

A fair number of studies suggest that there is a link, but those can be contrasted with other research that says there isn’t. The problem is that there are so many different factors to take into account, along with a swiftly-changing medium and difficulty in obtaining high-quality data—we'd need an avalanche of research to answer the question definitively.

While it's not an avalanche, a group of researchers, led by biological psychologist and video game violence skeptic Peter Etchells, has published an analysis suggesting that players of violent games might face a very small increase in risk for behavioral problems. They’re the kinds of small results that would be met with disappointment by authors who were hoping to find an effect, but they’re there. And yet, as always, this analysis isn’t the final word.

For a long time, archaeologists have suggested that modern humans wiped out Neanderthals because we had greater technological and cultural development, which allowed us to find and exploit resources more readily than Neanderthals did. It’s a plausible explanation, but it leaves us with pressing questions about the details of how this might have happened.

For a start, we know that Neanderthals had some culture, so exactly how much more would modern humans have needed to have in order to be more competitive? And modern humans entered Neanderthal territory in smaller numbers than the established Neanderthal population—could technology make up for what they lacked in numbers?

These questions highlight a major challenge with this model: there are other plausible explanations for the disappearance of Neanderthals. For example, they could have been wiped out by climate change or an epidemic.

If you’re not yet obsessed with crows, you’re behind the times. A flood of research on the birds keeps turning up astonishingly smart behavior. They use tools: in artificial captive situations, in the wild, and by exploiting urban features like traffic. They recognize human faces. They can solve complicated multi-step puzzles.

Despite all the ability, current research barely scratches the surface of the Internet’s love affair with these animals. Floods of anecdotes and videos attribute everything from gratitude to playfulness to the corvid family—colloquially known as crows. We can even watch them appearing to find entertainment in tormenting other animals, like these apparently mischievous (or sadistic) crows causing a cat fight.

It’s hard to escape the feeling that this playfulness tells us something important about crow intelligence—it seems intuitive to take it as a further sign of prodigious animal intellect. The problem is, animal behavior is notoriously tricky to interpret. We have a tendency to project our own minds onto animals, says Alex Kacelnik, a professor of behavioral ecology at Oxford University. “We see animals doing things for which we don’t have appropriate explanations other than pretending we ourselves are doing it.”

Humans are obviously pretty special when it comes to language. One of our cleverest tricks is the ability to process the sounds of spoken language at high speed—even more remarkable when you consider just how variable these sounds are. People have very different voices and very differently shaped throats and mouths, which all affect the sound waves that come out of them. And yet we have very little trouble communicating with speech.

There are many ways to try to figure out how this wizardry evolved, but one particularly useful source of information is birds. Their evolutionary relationship to humans goes pretty far back on the family tree, so anything unusual we have in common with them—like vocal learning—is unlikely to be because of our shared genetic history. Instead, it's more likely to result from similar evolutionary pressures causing both of us to hit on the similar solutions.

This is why a paper in this week's PNAS is so fascinating: it found that songbirds process sounds in a way that is very similar to humans. Like us, they're able to process how all the complex frequencies bound up in a single sound relate to one another. It’s very close to how humans process vowels.

Genetic evidence is an incredibly useful tool for understanding evolutionary history. It has helped us build up our current picture of how humans migrated out of Africa, and also estimate when chimps and humans parted ways from our last common ancestor.

Estimates that used different methods have placed the chimp-human split anywhere from 3 million to 10 million years ago (mya), sometimes falling far from the estimated 6-7 mya suggested by the fossil record—an indication that something is wrong in the calculations. But as researchers improve their techniques, the estimates are revised over and over again, each time hopefully getting closer to real picture.

Having the dates provided by the fossil record match the genetic evidence would help us to be more sure of our understanding, so it’s important to try to work out where the mismatch is and why it’s happening. Two researchers at Columbia University, Guy Amster and Guy Sella, have suggested an important factor that has been missing: the timing of life events like puberty and reproduction, and their effects on genetics. By building these factors into their calculations, they’ve come up with an estimate for the split that more closely matches the fossil records—around 6 mya.

The widely mocked stoner sloth anti-drug campaign typifies a long-held stereotype about marijuana—it makes you slow, stupid, dull. There’s been some research backing up the stereotype, suggesting that marijuana usage can be linked to declines in intellectual function.

But it’s hard to establish that marijuana is definitely the culprit. It’s not like conducting a clinical trial with marijuana would be feasible given the drug's status. So it’s necessary to look in other places for a ready-made control group that can help give a clearer picture of what’s causing the decline.

A paper in this week’s PNAS does just that by looking at marijuana use in twins. The research found that while there was a link between marijuana and lower scores on IQ tests, there seems to be another mystery factor underlying both the drug use and the cognitive decline.

A central premise in marketing seems so obvious that it doesn’t even bear scrutiny: if customers give you positive feedback on your product, that’s good. And if those people buy the product repeatedly, that's even better.

But what if certain customers just don’t have great taste? Or, more precisely, what if their tastes don’t match up with those of the rest of the population? Positive feedback and early sales from these customers might actually not be good news—they could be a sign that the product’s going to tank.

A recent paper in the Journal of Marketing Research has identified a group of customers whose support for a product is a “harbinger of failure,” a signal that the product will eventually flop. “Increased sales of a new product by some customers can actually be a strong signal of future failure,” researchers write. So who are these people?

Inbreeding to create purebred dogs has a deservedly bad reputation, as many of these breeds suffer from genetic diseases. But it turns out that it's not the only culprit. A paper in yesterday’s PNAS delves into the differences between wolf and dog genomes to find out exactly how human influence has increased the risk of dangerous mutation in dogs.

When dogs were first domesticated, they underwent what’s known as a population bottleneck. That is, only a small number of ancestral grey wolves formed the starter population for what eventually became dogs. This starter population had only a smidgen of the overall genetic diversity of wolves, and that’s all the genetic diversity that dogs started out with. Then, more recently, humans caused more bottlenecks when they started to selectively breed dogs. This narrows down the pool of genetic diversity even further.

To find out how these bottlenecks have affected dogs, the researchers sequenced the genomes of 46 dogs from 34 different breeds, as well as from 25 “village dogs,” the free-breeding dogs living in human settlements worldwide. They compared this to the genomes of 19 wolves.