Dogs Can Sniff Out Human Stress

A new study shows that the canine nose is sensitive enough to pick out distinctive compounds in the sweat of a person under pressure.


By Susan Pinker

Dogs are champion sniffers, equipped with 100 to 300 million olfactory receptors in their noses—compared with a mere 6 million in our own—and an olfactory cortex 40 times as large as ours. They can be trained to detect disease in human beings, including cancer cells, a latent epileptic seizure, or a Covid infection, just by sniffing—no blood samples, biopsies, MRIs, antigen or PCR tests required.

Can dogs smell something as ineffable as psychological distress? Mood disorders have surged since the onset of the Covid-19 pandemic and the demand for emotional support dogs has followed suit, with customers paying anywhere from $15,000 to $50,000 for a dog trained to respond right before a panic attack, or when the owner’s PTSD or addictive cravings bloom. Until recently, evidence that dogs can sniff out our psychological states remained anecdotal. “The assumption that dogs can identify a person’s psychological state is the reason why we have service dogs for PTSD, anxiety disorders and depression,” says Clara Wilson, a researcher at the Animal Behaviour Centre at Queens University Belfast. “It seems so obvious that no one has tested the idea empirically. Until now.”

In a study published in September in the journal PLoS One, Ms. Wilson and colleagues tested whether dogs can read and respond to our emotional states, without the benefit of facial expression, tone of voice, or social context. The researchers trained four dogs to detect and react to the smell of human stress, depending on their sense of smell alone to distinguish between a person’s baseline scent and the unique cocktail of volatile organic compounds (VOCs) in their sweat and breath when they’re feeling stressed out.

Using tasty rewards, the researchers trained the dogs to distinguish between three gauze samples. One was neutral, containing no human scent. The second had been breathed on and then wiped across the back of the neck of one of 36 human participants at a moment when they felt completely relaxed. The third set of sweat-and-breath samples was taken before and after the participant completed an arithmetic task under time pressure. The humans’ heart rate and blood pressure were monitored, to confirm that the smell of the gauze was indeed a sign of stress.

The goal was to teach the dog to pick out the “stress” sample from a set of three swatches and indicate it by sitting up in front of that sample, alert and attentive. To avoid giving the dog any inadvertent visual or social cues, each swatch was presented behind a grill, so it couldn’t be seen or touched, and no humans were present during the test. If the dog could pick out the stress sample from the distractors, he or she was rewarded with something good to eat.

The results offered overwhelming confirmation that dogs can smell psychological states as well as physical ones. On average, the four dogs picked out the stress sample 94% of the time, with individual dogs ranging between 90% and 97% accuracy. “There’s a smell to stress,” Ms. Wilson concludes. “If we can add it to the dog’s repertoire, we can use it to identify anxiety and panic attacks before they occur.”

Appeared in the October 22, 2022, print edition as ‘Dogs Can Sniff Out When a Human Is Stressed’.

The Risks of Having an Older Father

A new study finds that mice born to older fathers are more likely to struggle to communicate


By Susan Pinker

It is a source of envy for some women that older fathers can easily conceive healthy babies whereas older mothers, in many cases, cannot. When I had a child at the age of 35, my medical chart baldly stated that I was a “high-risk geriatric mother.”

Evidence is building, however, that older fathers also share some risk. Sperm cells generated later in a man’s life are more likely to feature genetic mutations that can lead to developmental disorders in children.

“There is evidence in humans that paternal aging is one of the risk factors for autism and other neurodevelopmental disorders,” said Noriko Osumi, a professor of developmental neuroscience at Tohoku University in Japan. “But there are a lot of confounding factors in humans. Is paternal aging itself really the cause, or is it something else?”

A new study led by Prof. Osumi involving newborn mice sheds light on the question. The study shows that mouse pups with older fathers are smaller and cry differently than those with younger dads. This can have negative consequences for the babies, she explained on a video call: “Some other [research] groups have noticed that if the baby’s type of cry is different, then the mother’s retrieval pattern changes.” A weird cry may mean that the mother isn’t primed to respond to the baby’s calls, in other words.

The research team, which includes first author Lingling Mai, a doctoral student in neuroscience at Tohoku University, included 120 mice. Half had fathers who were 3 months old, the equivalent of a human baby having a father in his 20s, while the other half had fathers between 1 and 2 years of age, comparable to having a human father in his 50s or 60s.

The mouse pups in the two groups were then separated from their mothers and littermates four times, at 3, 6, 9 and 12 days old. Each time the pups were placed in the “separation box,” their distress cries were recorded and analyzed. Under ordinary circumstances a human ear can’t hear these vocalizations, so the research team used special equipment and software to translate and graph the sound patterns, including downward or upward shifts in tone, harmonics, phrase repetitions and octave jumps.

A comparison between the two groups revealed that mice with young fathers were far more likely to have rich and complex cries than those with older fathers. The patterns of sound they emitted were also more likely to resemble each other. In comparison, the pups with older fathers cried less overall. Their vocalizations were more variable, yet had a more limited repertoire of sounds.

The study also found that pups with older fathers weighed less, which I expect may be related to the way they communicate. An animal with a sporadic, weak cry is likely to attract less attention from its mother, so it would nurse less and gain less weight.

Extending this finding to humans suggests that if infants don’t cry much in their first year, and use fewer words than other babies by their second birthday, parents should take notice. Sometimes parents say “my child is easy to raise because he doesn’t cry so much,” but that might not be such a good thing, suggested Prof. Osumi.

Appeared in the September 17, 2022, print edition as ‘The Risks of Having an Older Father’.

Early Lessons in Self-Control Bring Lifelong Benefits

Aggressive boys who got behavioral training show more stability as adults 30 years later


By Susan Pinker

In the early 1980s, a group of psychologists, led by Richard Tremblay of the University of Montreal, set out to study early behavior problems in 250 boys living in poor Montreal neighborhoods. The boys had been nominated by their teachers as highly aggressive, oppositional or hyperactive. All were native French speakers whose parents had no more than a high school education.

Researchers divided the boys, ages 7 to 9, into two groups at random by drawing their names from a box. Those in the treatment group received two years of coaching in social skills and self-control—with classes that involved verbal instruction, modeling and rehearsing desired behavior—and positive verbal and material feedback from adults. The instructors met separately with the child’s teacher and parents to bolster these lessons. The idea was to help the boys develop non-aggressive strategies for dealing with common social situations, like what to do if a classmate bumps your desk.

The boys in the control group, meanwhile, received the treatment typically offered to disruptive students at the time—being exiled to the corridor or the principal’s office.

The study aimed to see how such training might affect these high-risk boys over time, so the researchers followed up with them from ages 10 to 24. They found a large improvement in the self-control, attention and social skills of the boys in the treatment group. By late adolescence, these boys also performed better academically. And in early adulthood, they were more likely to be members of a social group.

Now, more than 30 years later, Dr. Tremblay and a new set of colleagues, including the French economist Yann Algan and doctoral candidate Elizabeth Beasley, have returned to the experiment to examine the progress of the boys as they have become men. Their new study, recently published in the American Economic Review, used school and government records to see whether the original participants graduated from high school, had police records and were employed. They also looked at how much tax they paid, their marital status and whether they received social assistance.

It turns out that early intervention made a significant difference for the participants—and society—in the long run. Of the highly aggressive boys who didn’t receive special coaching, 69% dropped out of high school, and 32% had a criminal record. Among the boys in the treatment group, 55% dropped out, and 21% had a criminal record. As adults, men who had been in the treatment group were more likely to be married, earned some 20% more a year and were 40% less likely to rely on welfare or unemployment insurance.

The idea for the original study came from Dr. Tremblay, who started his career in Montreal at what was then the Pinel Institute for the Criminally Insane (now the Philipe Pinel National Institute of Legal Psychiatry). Then as now, most of the men at the Institute had committed violent crimes. “I worked for three years with these mentally ill offenders, and almost all of them had killed someone,” Dr. Tremblay told me. “I decided then to focus on juveniles and possible juvenile delinquents.”

This remarkable experiment shows that early treatment can have an outsize impact on the lives of vulnerable boys. The researchers conclude, “We estimate that $1 invested in this program around age 8 yields about $11 in benefits by age 39.”

It would seem that there is little to be gained and much to lose if we take the watch-and-wait approach with disruptive little boys. The stakes are just too high.

Appeared in the August 13, 2022, print edition as ‘Early Lessons In Self-Control Bring Life-Long Benefits’.

How the Upwardly Mobile Feel About Wealth

A new study suggests that people who become affluent have less sympathy for the poor than the born rich do


By Susan Pinker

The rags-to-riches story is such an enduring part of American identity that it somehow feels unpatriotic to doubt it. Consider celebrities like Dolly Parton, Ray Charles or Arnold Schwarzenegger—to name just a few—who grew up poor and succeeded through outsize talent and sheer grit. Those who were born rich, however, don’t get the same respect. In a 2012 Pew Research Survey, just 27% of respondents said they admired the rich, but when a follow-up question asked whether they admired those who had earned their wealth, 88% agreed.

This gap is explored in a recent study published in the journal Social Psychological and Personality Science. The lead author, Hyunjin Koo, a doctoral candidate in psychology at the University of California, Irvine, explained why she was drawn to investigating the nuances of the American Dream: “People seem to really like and admire those who pulled themselves up by their own bootstraps, and expect them to care about the poor and about social welfare,” she wrote in an email.

Ms. Koo wondered whether people who started out at the bottom and achieved high status would support public policies to assist other strivers like themselves. Or, having successfully climbed the socioeconomic ladder, would they perceive upward social mobility as less difficult? “If I did it, why can’t they do it?” Ms. Koo asked rhetorically.

The research team, which included psychology professors Paul Piff at U.C. Irvine and Azim Shariff at the University of British Columbia, began with two studies designed to assess Americans’ attitudes to the rich. Six hundred randomly selected adults were asked to rate two groups: the “born rich,” who had inherited their wealth, and the “became rich,” who had earned it. Which group would be more likely to attribute poverty to external circumstances, for example, or feel empathy toward the poor?

The results showed that people considered the “became rich” more likable and also expected them to be more supportive of the less fortunate. A second set of studies, however, found that these attitudes aren’t in line with reality. This time the research group recruited 1,000 people whose earnings were in America’s top quintile, or more than $142,500 a year. The researchers then sorted this sample into two camps, the “born rich” and the “became rich,” by parsing their financial histories on a questionnaire.

Both groups were then asked to rate themselves on statements like “I demand the best because I’m worth it,” “I sometimes feel guilty about how much money I have compared to others,” and “In the U.S., it is difficult to improve one’s socioeconomic conditions.” In tabulating their answers, the researchers discovered that people who inherited their wealth were more likely to sympathize with those living in poverty and also more likely to support policies that would give the poor a leg up.

It’s the reverse of what one might expect. “People assume that those who had to climb the ladder better understand the struggle and therefore will be more sympathetic to the poor. Maybe they do understand, but the conclusion they come to is that it’s actually less of a struggle and thus less sympathy is in order,” said Prof. Shariff.

How Children Use Conflict to Win Popularity

New research shows that as early as the third grade, a student’s concerted aggression can raise their status among schoolmates


By Susan Pinker

If you’ve ever watched someone start an argument just to win it, then you’ve witnessed a maneuver the person has likely been honing since third grade. Stirring up conflict is how some young children manage to achieve top-dog status, according to a study recently published in the journal Personality and Individual Differences.

The idea that aggression can stoke a certain popularity isn’t new, says Brett Laursen, the lead author and a psychology professor at Florida Atlantic University. But the study showed a pattern among schoolchildren that stemmed from aggressors creating repeated conflicts; classmates would often submit rather than engage.

When researchers use the term “popularity” to describe the type of status involved, it’s not the usual connotation. “We don’t mean that other kids really like these kids,” said Dr. Laursen. “It’s more a sign of dominance. Popular kids set standards and control resources, like who sits next to you at lunch, or who gets invited to your birthday party, or who pays attention to you.”

Aggression doesn’t necessarily mean using physical force, he said. “Always hitting other kids can backfire. It’s much safer to use conflict—without hitting—to get others to back down…You just need disagreements where people demonstrate their fealty to you, because they’re afraid of what might happen.” Yet being aggressive in order to climb the social ladder doesn’t work for everyone, he added. “That’s the head scratcher.”

To explore the issue, Dr. Laursen, working with doctoral candidates Michael Yoho and Sharon Faur, asked 356 elementary-school students—all third-, fourth- and fifth-graders—to fill out detailed questionnaires near the beginning of their fall semester. The kids were queried about their opinions and beliefs, and about how many disagreements they’d had the day before and with whom. They were asked to nominate classmates who “talk bad about others behind their backs,” who “get into trouble at school, or who “hit, push or shove others.” There were also questions about who the students would choose to spend time with or avoid. Thus, the researchers got an overview of the social dynamics of each class near the beginning of the year. At the end of the semester, the researchers asked the same students to complete the questionnaires again.

The results showed that children who maintained a frequent pattern of aggression had raised their status at the end of the term, while those who didn’t continue their confrontational behavior failed to get the popularity boost. In short, a small number of students in each grade kept initiating disagreement, presumably with the intention to command respect. Dr. Laursen added, “Most of these disagreements were not big arguments, but rather displays of dominance, say, overruling someone’s suggestion, just to let others know who’s the boss.”

What sets these students apart is their tendency to “think strategically about manipulating others,” suggested Dr. Laursen, adding that it’s likely a lasting trait. “For people who care about their status, a disagreement is never just a disagreement. Whether you’re 15 or 50, everything is an exercise in maintaining and improving popularity.”

Other research has shown that such belligerent behavior, rather than being penalized, is rewarded even more at older ages. That may paint a bleak picture of our social world, but at least it describes only a small cohort of people. As Dr. Laursen points out, society tends to rely on pecking orders of one kind or another. Perhaps some of these younger toughs will yet have time to find less combative ways to rise in status. We can only hope.

To Enjoy Social Contact, Choice Matters

 New research shows that people are least happy when they don’t have control over whether to spend time alone or in a group

By Susan Pinker

Whether our homes became refuges or prisons over the last two years, there is no doubt that the pandemic dramatically curtailed our social autonomy. We could no longer decide if and when to socialize, or even with whom. If we were lucky enough to have a home, we were stuck with our fellow inmates.

Research just published in the Journal of Happiness Studies now reveals that when it comes to happiness, having a choice is key. People who don’t choose to be social but end up surrounded by other people rate themselves as unhappiest. In contrast, folks who opt to be social and then find themselves in the company of others were ecstatic.

“Our culture is so focused on how positive interactions can be—just think of FOMO—that we don’t consider the alternative,” said the study’s lead author Liad Uziel, a psychology professor at Bar-Ilan University in Israel. “If you choose to be in a social situation, then you are likely to get more out of it. But your well-being is likely to drop if you didn’t choose it.”

The occasional period of time alone brings happiness to everyone, as long as that person chooses it.

The study, published with fellow Bar-Ilan psychology professor Tomer Schmidt-Barad, recruited 155 university students as participants. Every time the students received a text reminder on their phones, they had to report what they were doing and with whom, if they had any control over who they were with, and how they felt about it all. As Dr. Uziel described it: “How satisfied were they—their positive and negative experiences at that moment, how meaningful they found what was going on at that time, and how much control they had over the situation they were in.” The participants were pinged three times a day for a total of 10 weekdays, which yielded a mountain of data: 4,300 status reports.

Once the numbers were crunched, the researchers discerned several patterns. When people found themselves in social environments, whether chosen or unchosen, participants’ ratings of their experiences tended to the extreme, with higher highs and lower lows. “This means that our emotions are so much more intense when we’re with other people compared to when we’re alone,” Dr. Uziel said. Participants found themselves in environments they hadn’t chosen—such as classrooms and workplaces—about 30% of the time.

Being alone is more predictable, while being with others always presents surprises, he added. He used watching a soccer game as an example: “When you are alone and your team scores a goal, it’s exciting. But it’s way more exciting if you’re with other people—you experience it more powerfully.” This doesn’t mean that time alone is to be avoided, he said; the data show that “the occasional period of time alone brings happiness to everyone, as long as that person chooses it.”

Being with others also means having an audience, which heightens the impact of any experience. Performers know this, as does anyone who has ever watched a 5-year-old learning to ride a bike. Having an audience witness your achievement feels glorious. Of course, falling off your bike repeatedly is embarrassing when there’s an audience. These are the extremes of feeling that Dr. Uziel said were typical of social situations, whether or not they were chosen.

His next project will be to look at how the pandemic has changed the meaning of social situations. “It’s a risk, even for people who like to be with others,” Dr. Uziel said. “We shouldn’t push people to socialize.”

This dictum, he suggested, should influence how we design workplaces and family homes: “Give people as much choice as possible. Because forcing social contact on people is just a source of stress.”

There’s a Secret to Keeping Secrets

Research shows that a confidant who objects to the behavior that’s being hidden is more likely to spill the beans


By Susan Pinker

In a perfect world, our secrets would always be kept. But our world is imperfect. New research concludes that confidences about shame-inducing missteps, infidelities and imbroglios get exposed about a third of the time, which raises the question: What kinds of secrets are most likely to be revealed?

Jessica Salerno, a psychology professor at Arizona State University, and Michael Slepian, a professor of leadership and ethics at Columbia Business School, address this and other issues in a study published last month in the Journal of Personality and Social Psychology. Building on their own previous work and that of colleagues, they explore the nexus between secrecy and morality.

Dr. Slepian and Dr. Salerno were intrigued by the 2015 breach of the Ashley Madison website, which was created to help married people meet partners online in order to have affairs. The hackers “released all the data, which was hugely sensitive,” because they found the site morally objectionable, Dr. Slepian said. The two researchers set up a series of experiments and surveys to probe whether people were more likely to expose others’ secrets if they wanted to punish their behavior, as was the case with Ashley Madison.

Assembling nine different groups of 150 diverse participants, the researchers employed a variety of scenarios involving secrets that were hypothetical or taken from the news, or from the participants’ own experience. Some involved behavior that participants might find immoral; in a subset of those scenarios, the person committing the secret transgression had already been punished in some way. In each mini-experiment, details were subtly tweaked to see how the participants’ answers would differ. Was the secret act intentional or accidental, for example, or was anyone harmed? Participants were asked whether they supported disclosing someone’s secrets in each case.

The results showed that people were more likely to approve of spilling the beans if they found the secret behavior unethical. “The more morally outraged they felt, the more likely they were to reveal the secret,” said Dr. Salerno. In general, the moral code of the supposed confidante predicted their willingness to blab.

The secrets most likely to be revealed include specific lies (46%), harming another person or yourself (40%), illegal behavior (35%) and drug use (34%). By contrast, a confidence about a surprise event would only be revealed 18% of the time. If the secret was about someone who had already faced consequences for their behavior, a confidante would be less likely to reveal their secret because they’d already been punished, added Dr. Slepian. If the hidden behavior was unintentional, the secret was also likelier to be kept under wraps.

So how do you find a true confidant? Drawing on previous research, Dr. Slepian suggests avoiding the polite, rule-following, easy-to-offend person, especially if outgoing and loquacious; that’s the profile of someone most likely to spill the beans.

“What you really want is someone compassionate and assertive—especially if you’re looking for help—and someone who has the same sense of morality as you,” Dr. Salerno said. As she emphasized, keeping secrets is always difficult, but it’s especially hard if the shared information induces indignation or disapproval in your confidant.

A Gender Split Over Sniffing a Baby’s Scalp

Mothers get more aggressive and fathers less so when they inhale a chemical found in abundance on infants’ heads


By Susan Pinker

Imagine there was an odorless substance that made men less aggressive when they inhaled it but had the opposite effect on women. Sniffing it made women bolder. Would you go online and immediately click “buy”?

There’s no need: Our bodies produce this substance already. Hexadecanal, or HEX, is one of 6,000 volatile chemicals emitted by our body secretions, like tears and sweat, and in HEX’s case, by an infant’s scalp. Chemical signals like HEX fly under our conscious radar while altering our behavior, said Noam Sobel, a professor of neurobiology at Israel’s Weizmann Institute of Science, who calls his lab “very nose-centric.”

Two experiments—recently published in the journal Science Advances by Prof. Sobel, data scientist Eva Mishor and a team of colleagues—revealed that breathing in HEX influences our social behavior, dialing up aggression in women but attenuating it in men. This sex difference stunned the researchers. Based on mouse studies, they expected HEX to have a calming effect across the board. “Until the end of the second study I was skeptical about the results. HEX has no odor, yet our body reacts to it, and our behavior changes,” said Dr. Mishor.

The researchers made this discovery through a classic double-blind study in which 127 people were randomly assigned to an experimental or a control group, either inhaling clove oil infused with HEX or clove oil alone. Both groups played a computer-based negotiation game, believing that they were interacting with a remote opponent.

In reality the participants were playing against an algorithm that offered them egregiously unfair financial deals. “The ‘opponent’ proposes that he get 90% of a sum of money while you get 10%,” said Prof. Sobel, for example, and by the time participants reached the next phase of the experiment “they’re really mad at this person because they’re being so antisocial.”

That’s when the participants moved to a reaction-time game in which they could exact their revenge. When their “opponent” lost a round, the subject could punish them with a horn blast at different volumes, each illustrated by a face showing increasing signs of distress. “What we saw was a small but consistent difference between the HEX and the control subjects,” said Dr. Mishor. “Women exposed to HEX reacted 19% more aggressively, while men were 18.5% less aggressive.”

This was such an unexpected finding that the researchers did a second experiment. This time participants were tested while in a brain scanner. They were compared with themselves after inhaling either HEX or a dummy liquid. After being made to believe that money was being stolen from them in the game, would the same person react the same way in both conditions? Again, the women reacted with more aggression when exposed to HEX vs. the control liquid, this time by extracting more money from their “opponent” as retribution, while the men reacted less aggressively when exposed to HEX.

In the HEX condition, the men’s scans also showed greater connectivity to other areas of the brain, suggesting more neural engagement in regions that might control aggression. “We can look at the functional connectivity alone and distinguish men from women at 86% accuracy,” said Prof. Sobel.

What to make of the findings? The authors speculate that HEX is an ancient survival mechanism. Mothers exposed to the chemical signal would be more likely to defend their babies against threats, while fathers who inhale it would likely be less aggressive. Excited by the finding, Prof. Sobel thinks this is just the beginning of investigating olfaction as a driver of human aggression. “The next stage is to do this with actual babies’ heads instead of HEX in a jar.”

How to Bee Socially Distanced

Members of a hive instinctively stay farther apart when they sense a viral intruder.

illustration of bee's socially distancing


By Susan Pinker

Ants do it, bees do it, even baboons in the trees do it. Let’s do it, let’s keep our distance. It’s not so easy for humans, it seems, even when a contagious disease is rapidly spreading. But for honey bees? No problem. A study published last month in the journal Science Advances shows that honeybees start social distancing as soon as a bee brings a dangerous parasite into the hive.

Worthy of its name, the varroa destructor mite carries a virus that can destroy the colony from within. But the presence of the parasite is noticed by the colony’s healthy bees, who change their behavior to limit viral transmission, according to a suite of experiments led by Michelina Pusceddu and Alberto Satta, agricultural researchers at the University of Sassari, Italy, along with colleagues at three other European universities. “Varroa destructor is among the most serious threats to honey bees world-wide and has played a fundamental role in the decline of honey bee colonies all over the Northern Hemisphere in the past decades,” they write.

It’s a scientific parable for our times: A deadly virus descends on us out of the blue and exploits our social habits to expand its territory and reproduce. We’d be goners, except that evolutionarily speaking, a social species has a couple of ways to fight back. In some social animals, like ants, chimps and gorillas, the infected animal acts first: It might move slowly and look a little mangy, or skulk off to self-isolate. Other members of the group then know to avoid it.

But in the noble honeybee, the pest’s intrusion immediately alters the behavior of the healthy forager bees, who know their colony members by smell and can distinguish between the scent of healthy nest mates and those carrying parasites. The presence of the parasite in the colony prompts them to shift their activities away from the uninfected and more vulnerable members of the hive—the queen, the babies and their nurses.

The study’s authors call this change in the healthy bees’ behavior social distancing, and they expected to see more of it in the infested hives. Their experiment consisted of observing the behavior of bees in six colonies. Half of the hives had been regularly treated with oxalic acid, a natural pesticide, to make sure they were mite-free. A varroa destructor infestation bloomed naturally in the other three hives. The researchers videorecorded what went on in the hives over three consecutive days.

Forager bees are the explorers who leave the hive to find the nectar that nourishes the colony. Upon their return, they communicate where the sweetest flowers are, how big the nectar cache is and whether more foragers are needed. They do this by executing a waggle and vibration dance in the shape of a figure eight.

The comparison among hives revealed a stark difference in the forager bees’ dances, depending on the presence of infection. When the researchers compared the varroa-infested hives with uninfested ones, they found that the number of foraging dances was the same in the two groups, but the location of the dance floor differed. In the infected hives, the foragers were more likely to stay on the perimeter of the hive. In the uninfected hives, the foragers danced and waggled to their hearts’ content in the inner sanctum.

“The frequency of dances on the outermost frames is about 70% in infested colonies, compared with 10% in the uninfested colonies. So I would say that the probability of foragers being at the outer limits of the hive in infested colonies is seven times as likely as in uninfested colonies,” wrote Dr. Satta in an email.

Even one-day-old bees changed their behavior when detecting infection around them. They groomed each other more—which removed the mites—and fed and rubbed their antennae against nest-mates less. In other words, the presence of disease changed their social habits. If one-day-old honeybees can do it, so can we.

What Dogs Do and Don’t Understand

Our canine friends don’t get the meaning of our words without extra cues, research shows—but they do learn to anticipate what we say


By Susan Pinker

“Milo, leave it!” “Forest, come here right now!” “Louis, let’s go. I’ve got a conference call.” Most dog owners talk to their dogs and assume they understand what they say, and I’m no different. I tell 75-pound Otis to stop barking at dogs passing by, and he sometimes listens. I admit to using a high-pitched form of baby talk to narrate our walks, pointing out the forgotten tennis ball or the squirrel he shouldn’t chase, enunciating as if he were a human toddler.

But he’s not. We like to think that our dogs understand what we say, but the scientific evidence for true language comprehension in dogs is sparse. A few dogs are gifted. As a 2004 study in the journal Science showed, a border collie named Rico in Leipzig, Germany, could understand 200 words and execute precise verbal commands. But when all other cues are controlled for, the scientific consensus is that context, gesture and tone of voice signify much more to the average dog than human speech does.

“When it comes to lab conditions, it turns out that dogs are not good at word meanings,” said Marianna Boros, a postdoctoral researcher at Eötvös Loránd University in Hungary. Most need gestures and intonations to understand. She adds: “This is also true of commands like ‘sit.’”

Them’s fighting words for many dog lovers, but Dr. Boros knows whereof she speaks. Her research group is one of several at the Budapest school that specialize in canine cognition. The researchers haven’t found evidence for word comprehension in dogs per se. But they have discovered some of its neural scaffolding, such as a right-hemisphere bias for language processing in dogs’ brains, which is opposite to that of humans. They have also shown, using functional MRI scans of brain activity, that dogs know when a word and its intonation match.

Now they have proof that dogs can pick up on the boundaries separating words while listening to speech recorded without pauses and in a monotone, according to a new study led by Dr. Boros and Lilla Magyari, to be published in the journal Current Biology next month. Not only can dogs sense where a word begins and ends, but they can compute the probability that a certain syllable will appear next, much as our smartphones predict what we will tap next in a text or email.

To get access to such arcane canine data, the researchers used brain imaging on 37 dogs; 19 were tested by electroencephalogram and another 18 were trained to jump into the MRI scanner—which they did willingly and with tails wagging—to listen to speech samples.

The dogs’ brain responses showed that they could follow two rules: They note how frequently they hear two syllables together, and they compute how likely two particular syllables are to follow each other. This hasn’t been shown in nonhuman mammals before, though it has been shown in 8-month-old infants.

Dr. Boros’s study showed that dogs use some of the same neural hardware as babies do to detect word and syllable probabilities: the basal ganglia, which supports sequential and pattern learning, and the auditory cortex, one of the areas specialized for language.

While this doesn’t mean that dogs understand the meanings of words, it tells us that recognizing the building blocks of language is not unique to humans. “It suggests that the ability to segment speech is a general mammalian capacity” that may have evolved or been acquired by dogs while living alongside humans, said Dr. Boros.

In short, our babies, our smartphones—and even our dogs—can handily detect and predict what we might say or write next. As long as none of them actually finishes my sentences or tells me to “sit,” that’s fine with me.

Appeared in the November 20, 2021, print edition.