A new study suggests that human intelligence may have evolved in response to the demands of caring for infants.
Steven Piantadosi and Celeste Kidd, assistant professors in brain and cognitive sciences, developed a novel evolutionary model in which the progression of high levels of intelligence may be driven by the demands of raising offspring. Their meta-analysis study is available online in the Proceedings of the National Academy of Sciences’ Early Edition.
“Human infants are born far more immature than the infants of other species. For example, giraffe calves are able to stand-up, walk around, and even flee from predators within hours of their births. By comparison, human infants cannot even support their own heads,” said Kidd.
“Our theory is that there is a kind of self-reinforcing cycle where big brains lead to very premature offspring and premature offspring lead to parents having to have big brains. What our formal modeling work shows is that those dynamics can result in runaway pressure for extremely intelligent parents and extremely premature offspring,” said Piantadosi.
In other words, because humans have relatively big brains, their infants must be born early in development while their heads are still small enough to ensure a safe delivery. Early birth, though, means that human infants are helpless for much longer than other primates, and such vulnerable infants require intelligent parents. As a result, selective pressures for large brains and early birth can become self-reinforcing—potentially creating species like humans with qualitatively different cognitive abilities than other animals.
Piantadosi and Kidd tested a novel prediction of the model that the immaturity of newborns should be strongly related to general intelligence. “What we found is that weaning time—which acts as a measure of the prematurity of the infants—was a much better predictor of primate’s intelligence than any of other measures we looked at, including brain size, which is commonly correlated with intelligence,” said Piantadosi.
The theory may also be able to explain the origin of the cognitive abilities that make humans special. “Humans have a unique kind of intelligence. We are good at social reasoning and something called ‘theory of mind’—the ability to anticipate the needs of others, and to recognize that those needs may not be the same as our own,” said Kidd, who is also the director of the Rochester Baby Lab. “This is an especially helpful when taking care of an infant who is not able talk for a couple of years.”
“There are alternative theories of why humans are so intelligent. A lot of these are based on factors like living in a harsh environment or hunting in groups,” said Piantadosi. “One of the motivating puzzles of our research was thinking about those theories and trying to see why they predict specifically that primates or mammals should become so intelligent, instead of other species that faced similar pressures.”
The key is live birth. According to the researchers, the runaway selection of intelligence requires both live birth of a single offspring and large brains—distinctive features of higher mammals.
“Our theory explains specifically why primates developed superintelligence but dinosaurs—who faced many of the same environmental pressures and had more time to do so—did not. Dinosaurs matured in eggs, so there was no linking between intelligence and infant immaturity at birth,” said Kidd.
Even before infants understand their first words, they have already begun to link language and thought. Listening to language boosts infant cognition. New evidence provides even greater insight into the crucial role of language exposure in infants’ first months of life, according to Northwestern University research.
Prior research has found that infants come into the world equipped with an initially broad link, one that encompasses the communicative signals of both humans and nonhuman primates. At 3 months old, listening to both human and nonhuman primate (lemur) vocalizations supports infants’ ability to form categories, a building block of cognition. But by 6 months, the link has narrowed, with only human vocalizations supporting categorization. Infants’ initially broad link to cognition is sculpted by their experience.
Northwestern researchers sought to understand what mechanisms underlie this rapid tuning process and document in a new study the crucial role of experience as infants tune this link specifically to human language.
In the experiments, the researchers found that merely exposing 6-month-old infants to nonhuman primate vocalizations permits them to preserve, rather than sever, their early link between these signals and categorization. Exposing infants to backward human speech – a signal that fails to support categorization in the first year of life – does not have this advantage.
“This new evidence illuminates the central role of early experience as infants specify which signals, from an initially broad set, they will continue to link to core cognitive capacities,” said
Danielle R. Perszyk, lead author of the study and a doctoral candidate in cognitive psychology in the Weinberg College of Arts and Sciences at Northwestern.
The research, which underscores the importance of language exposure in the first months of life, also has far-reaching implications for early language and cognitive development.
“It provides a unique vantage point from which to consider the intricate interface between capacities inherent in the human infant and the shaping force of experience,” said Sandra Waxman, senior author of the study, director of the Project on Child Development, faculty fellow in Northwestern’s Institute for Policy Research and the Louis W. Menk Chair in Psychology at Northwestern.
“Although experience may play little, if any role, in picking out the broad set of signals that infants first link to cognition, here we show that experience is essential in guiding infants, with increasing precision, to single out which signals from the initially privileged set they will continue to link to meaning and which they will tune out,” Waxman said.
A baby’s cry not only commands our attention, it also rattles our executive functions—the very neural and cognitive processes we use for making everyday decisions, according to a new University of Toronto study.
“Parental instinct appears to be hardwired, yet no one talks about how this instinct might include cognition,” says David Haley, co-author and Associate Professor of psychology at U of T Scarborough.
“If we simply had an automatic response every time a baby started crying, how would we think about competing concerns in the environment or how best to respond to a baby’s distress?”
The study looked at the effect infant vocalizations—in this case audio clips of a baby laughing or crying—had on adults completing a cognitive conflict task. The researchers used the Stroop task, in which participants were asked to rapidly identify the color of a printed word while ignoring the meaning of the word itself. Brain activity was measured using electroencephalography (EEG) during each trial of the cognitive task, which took place immediately after a two-second audio clip of an infant vocalization.
The brain data revealed that the infant cries reduced attention to the task and triggered greater cognitive conflict processing than the infant laughs. Cognitive conflict processing is important because it controls attention—one of the most basic executive functions needed to complete a task or make a decision, notes Haley, who runs U of T’s Parent-Infant Research Lab.
“Parents are constantly making a variety of everyday decisions and have competing demands on their attention,” says Joanna Dudek, a graduate student in Haley’s Parent-Infant Research Lab and the lead author of the study.
“They may be in the middle of doing chores when the doorbell rings and their child starts to cry. How do they stay calm, cool and collected, and how do they know when to drop what they’re doing and pick up the child?”
A baby’s cry has been shown to cause aversion in adults, but it could also create an adaptive response by “switching on” the cognitive control parents use in effectively responding to their child’s emotional needs while also addressing other demands in everyday life, adds Haley.
“If an infant’s cry activates cognitive conflict in the brain, it could also be teaching parents how to focus their attention more selectively,” he says.
“It’s this cognitive flexibility that allows parents to rapidly switch between responding to their baby’s distress and other competing demands in their lives—which, paradoxically, may mean ignoring the infant momentarily.”
The findings add to a growing body of research suggesting that infants occupy a privileged status in our neurobiological programming, one deeply rooted in our evolutionary past. But, as Haley notes, it also reveals an important adaptive cognitive function in the human brain.
Release of Chemical Dopamine in Infant Brains May Help Control Early Social Development
Changing levels of the chemical dopamine, a chemical most associated with motivation, may help explain why stressful experiences during infancy can lead to lasting behavioral issues, a new study in rodents shows.
Experts have long understood that negative experiences early in life among rodents and other mammals, including humans, can affect later social development. Past studies in rats, for example, have found that limited bedding causes mother rats to roughly handle pups, impacting pups’ social behavior throughout their lives. However, exactly what changes occurred in the brain as a result of such adversity remained unclear.
In a study led by researchers at NYU Grossman School of Medicine, investigators tied repeated stress during infancy to increased dopamine levels in the basolateral amygdala (BLA), a brain region that plays a role in memory formation. When they housed mother rats and their new pups in stressful conditions while rearing their young, the stressed pups had about twice as much BLA activity compared with those raised in a more comfortable nest. In turn, the former group spent at least 90 percent less time near their mothers and more than 30 percent less time near other pups compared with the latter group.
“Our findings suggest that repeated dopamine release in the basolateral amygdala plays a key role in infant social development,” says study lead author Maya Opendak, PhD. “As a result, this region of the brain may be a promising target for understanding or even treating psychiatric disorders that can interfere with social interaction, such as autism,anxiety, and depression.”
As part of the study, the study authors artificially blocked dopamine release in the BLA in the distressed infants and found that social behavior returned to normal. By contrast, increasing dopamine levels in pups raised in non-stressful conditions impaired their social behavior.
Dr. Opendak, a postdoctoral research fellow in the Department of Child and Adolescent Psychiatry at NYU Langone Health, notes that elevated BLA activity and social impairment only occurred in pups that were stressed in their mother’s presence. If they experienced stress alone, they showed no sign of these issues. Dr. Opendak suggests that the repeated activation of the BLA, already known to play a key role in learning about threats, prompts infants to associate their mother with danger.
“Our investigation offered us a clearer look at how specific brain mechanisms link stressful experiences during infancy to lifelong social behavior problems,” says study senior author Regina M. Sullivan, PhD. “We can take this same approach to explore other areas of brain development, such as memory, learning, and threat recognition,” adds Dr. Sullivan, a professor in the Department of Child and Adolescent Psychiatry.
For the study, published online in the journal Neuron, the research team observed the behavior of hundreds of rat pups. Some rodent mothers were provided limited materials with which to build a nest. In a series of social behavior tests, the study authors measured the length of time pups approached their mothers or peers after five days of living in these stressful conditions. According to the findings, the longer the stress exposure went on, the less often the pups would approach their mothers.
To examine the role of dopamine during these early life experiences, researchers used drugs that block the chemical’s release in the brain. They also stimulated dopamine release in individual brain cells using light to test the impact of the chemical on social behavior after distress.
Dr. Sullivan says the research team next plans to expand the investigation to other brain areas involved in processing threat and reward.
She cautions that the study only explored the effect of a single chemical in one brain pathway, noting that social behavior involves an intricate network of cells and other pathways that still needs to be uncovered.
CDC researchers reported a 10% increase in deaths from cardiac arrest in 15-34-year-olds over the seven-year period from 1989 to 1996—a finding reiterated in 2012 by the American Academy of Pediatrics. The increase translated into about 3,000 deaths annually by the mid-1990s. Although more recent numbers are harder to come by, in 2015, the American Heart Association reported over 6,300 “out-of-hospital cardiac arrests” in American youth less than 18 years of age, citing survival rates ranging from about 10% to 31%. A single state (Michigan) reported an average of 35 sudden cardiac deaths a year in children and teens under age 20 as of 2009.
Midwife-friendly laws and regulations tend to coincide with lower rates of premature births, cesarean deliveries and newborn deaths, according to a U.S.-wide “report card” that ranks each of the 50 states on the quality of their maternity care.
The first-of-its-kind study found a strong connection between the role of midwives in the health care system – what the researchers call “midwifery integration” – and birth outcomes. States with high midwifery integration, like Washington and Oregon, generally had better results, while states with the least integration, primarily in the Midwest and South, tended to do worse.
As with most population health studies, the statistical association between the role of midwives and birth outcomes doesn’t prove a cause-and-effect relationship. Other factors, especially race, loom larger, with African-Americans experiencing a disproportionate share of negative outcomes. However, almost 12 percent of the variation in neonatal death across the U.S. is attributable solely to how much of a part midwives play in each state’s health care system.
“Our results show that families experience better outcomes when midwives can practice to their full capacity and are part of the system,” said Saraswathi Vedam, an Associate Professor in the Department of Family Practice at the University of British Columbia, who led the team of U.S. epidemiology and health policy researchers responsible for the study, published Feb. 21 in PLOS ONE. “In marginalized communities in the U.S., where the health system is often stretched thin, expanding access to midwives and increasing their responsibilities could be a feasible strategy for improving maternity care.”
McLean Hospital neuroscientists have found that even a brief episode of immune system activation within days of birth can cause persistent changes in sleep patterns concurrent with increases in epilepsy-like brain activity—a combination of symptoms common in autism spectrum disorder (ASD) and other developmental conditions. The detailed findings are available in the January 12, 2018 issue of Neuropsychopharmacology.
“A growing body of evidence suggests that immune system activation, such as that caused by bacterial and viral infections, can play important roles in many brain disorders,” explained Bill Carlezon, PhD, chief of the Division of Basic Neuroscience at McLean Hospital, and senior author of the paper. “While previous research in laboratory animals has established that immune activation during critical prenatal (before birth) developmental periods can later produce the core features of ASD, including decreased social interaction, aberrant communication, and increased repetitive behavior, we wanted to evaluate whether postnatal (during infancy) immune activation could also produce other symptom clusters that are often seen in ASD and related conditions.”
Full open access research for “Perinatal Immune Activation Produces Persistent Sleep Alterations and Epileptiform Activity in Male Mice” by Galen Missig, Emery L Mokler, James O Robbins, Abigail J Alexander, Christopher J McDougle & William A Carlezon Jr in Neuropsychopharmacology. Published online October 6 2017 doi:not available
Holy shit. This is brand-new news, guys–the linked article was published May 11, and the scholarly paper came out earlier this week. (Appears to be open access at this time.)
The next thing, according to the article, is to develop a screening test to identify at-risk infants at birth–that’s expected to take several years, unfortunately, but it’ll make a huge difference, both to parents who will know to take every precaution (and, hopefully, some new ones that can be discovered now that this is known), and to ones who will learn that they can relax a bit about their child’s sleep position. It’ll also be of some help to parents who lose a baby to this, because they won’t have to deal with the extra burden of being suspected of having caused it.
yeah they drop them in like a real fall into a pool its an infant self rescue course its scary as hell to watch but it teaches your baby not to drown
No seriously it really is amazing. It’s called ISR Self Rescue. I’ve seen multiple parents on social media decide to do this with their babies as young as 6 months (they gradually get up to the “throwing” into the pool) and it’s so awesome watching it.
It literally could be a lifesaver some day. One time I watched a security camera video of a dad playing in a pool with his kids and his toddler, who had been sitting on the slide, fell in and the dad didn’t notice for at least 30 seconds… But this little toddler automatically knew what to do and started floating on his back. When the dad noticed, he immediately grabbed him, but the reason this toddler didn’t sink or drown was because of the infant swim lessons his parents had presumably put him in.
Obviously floaties and parental supervision would still help, but you can’t rely on those 100% of the time.
Oh thank you so much for explaining i was so worried
Crazy factoid: Babies are actually born knowing how to hold their breath and use swim-like movements when submerged. Yeah. It’s a primitive reflex that they lose (if not enforced) at ~6 months.
Obviously, do not submerge your infant in water without an expert, but what these lessons are doing is encouraging and honing natural reflexes. These babies are perfectly safe, and I honestly think this is a really responsible parenting move. Accidents happen. Floaties don’t know which side is up. Parents are humans, not robots, and especially with more than one kid, sometimes you look away for a minute. It happens. But lessons like these minimize the risk involved.
Children younger than about 18 months don’t recognize themselves in the mirror, and this video shows the development of self-awareness via this construct. So cute.
