Chimps Outplay Humans in Brain Games

We humans assume we are the smartest of all creations. In a world with over 8.7 million species, only we have the ability to understand the inner workings of our body while also unraveling the mysteries of the universe. We are the geniuses, the philosophers, the artists, the poets and savants. We amuse at a dog playing ball, a dolphin jumping rings, or a monkey imitating man because we think of these as remarkable acts for animals that, we presume, aren’t smart as us. But what is smart? Is it just about having ideas, or being good at language and math?

Scientists have shown, time and again, that many animals have an extraordinary intellect. Unlike an average human brain that can barely recall a vivid scene from the last hour, chimps have a photographic memory and can memorize patterns they see in the blink of an eye. Sea lions and elephants can remember faces from decades ago. Animals also have a unique sense perception. Sniffer dogs can detect the first signs of colon cancer by the scents of patients, while doctors flounder in early diagnosis. So the point is animals are smart too. But that’s not the upsetting realization. What happens when, for just once, a chimp or a dog challenges man to one of their feats? Well, for one, a precarious face-off – like the one Matt Reeves conceived in the Planet of the Apes – would seem a tad less unlikely than we thought.

In a recent study by psychologists Colin Camerer and Tetsuro Matsuzawa, chimps and humans played a strategy game – and unexpectedly, the chimps outplayed the humans.

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Status and the Brain

Social hierarchy is a fact of life for many animals. Navigating social hierarchy requires understanding one’s own status relative to others and behaving accordingly, while achieving higher status may call upon cunning and strategic thinking. The neural mechanisms mediating social status have become increasingly well understood in invertebrates and model organisms like fish and mice but until recently have remained more opaque in humans and other primates. In a new study in this issue, Noonan and colleagues explore the neural correlates of social rank in macaques. Using both structural and functional brain imaging, they found neural changes associated with individual monkeys’ social status, including alterations in the amygdala, hypothalamus, and brainstem—areas previously implicated in dominance-related behavior in other vertebrates. A separate but related network in the temporal and prefrontal cortex appears to mediate more cognitive aspects of strategic social behavior. These findings begin to delineate the neural circuits that enable us to navigate our own social worlds. A major remaining challenge is identifying how these networks contribute functionally to our social lives, which may open new avenues for developing innovative treatments for social disorders.

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Do not disturb! How the brain filters out distractions

You know the feeling? You are trying to dial a phone number from memory… you have to concentrate…. then someone starts shouting out other numbers nearby. In a situation like that, your brain must ignore the distraction as best it can so as not to lose vital information from its working memory. A new paper published in Neuron by a team of neurobiologists led by Professor Andreas Nieder at the University of Tübingen gives insight into just how the brain manages this problem.

The researchers put rhesus monkey in a similar situation. The monkeys had to remember the number of dots in an image and reproduce the knowledge a moment later. While they were taking in the information, a distraction was introduced, showing a different number of dots. And even though the monkeys were mostly able to ignore the distraction, their concentration was disturbed and their memory performance suffered.

Measurements of the electrical activity of nerve cells in two key areas of the brain showed a surprising result: nerve cells in the prefrontal cortex signaled the distraction while it was being presented, but immediately restored the remembered information (the number of dots) once the distraction was switched off. In contrast, nerve cells in the parietal cortex were unimpressed by the distraction and reliably transmitted the information about the correct number of dots.

These findings provide important clues about the strategies and division of labor among different parts of the brain when it comes to using the working memory. “Different parts of the brain appear to use different strategies to filter out distractions,” says Dr. Simon Jacob, who carried out research in Tübingen before switching to the Psychiatric Clinic at the Charité hospitals in Berlin. “Nerve cells in the parietal cortex simply suppress the distraction, while nerve cells in the prefrontal cortex allow themselves to be momentarily distracted – only to return immediately to the truly important memory content.”

The researchers were surprised by the two brain areas’ difference in sensitivity to distraction. “We had assumed that the prefrontal cortex is able to filter out all kinds of distractions, while the parietal cortex was considered more vulnerable to disturbances,” says Professor Nieder. “We will have to rethink that. The memory-storage tasks and the strategies of each brain area are distributed differently from what we expected.”

Insect diet helped early humans build bigger brains

Figuring out how to survive on a lean-season diet of hard-to-reach ants, slugs and other bugs may have spurred the development of bigger brains and higher-level cognitive functions in the ancestors of humans and other primates, suggests research from Washington University in St. Louis.

“Challenges associated with finding food have long been recognized as important in shaping evolution of the brain and cognition in primates, including humans,” said Amanda D. Melin, PhD, assistant professor of anthropology in Arts & Sciences and lead author of the study.

“Our work suggests that digging for insects when food was scarce may have contributed to hominid cognitive evolution and set the stage for advanced tool use.”

Based on a five-year study of capuchin monkeys in Costa Rica, the research provides support for an evolutionary theory that links the development of sensorimotor (SMI) skills, such as increased manual dexterity, tool use, and innovative problem solving, to the creative challenges of foraging for insects and other foods that are buried, embedded or otherwise hard to procure.

Published in the June 2014 Journal of Human Evolution, the study is the first to provide detailed evidence from the field on how seasonal changes in food supplies influence the foraging patterns of wild capuchin monkeys.

The study is co-authored by biologist Hilary C. Young and anthropologists Krisztina N. Mosdossy and Linda M. Fedigan, all from the University of Calgary, Canada.

It notes that many human populations also eat embedded insects on a seasonal basis and suggests that this practice played a key role in human evolution.

“We find that capuchin monkeys eat embedded insects year-round but intensify their feeding seasonally, during the time that their preferred food – ripe fruit – is less abundant,” Melin said. “These results suggest embedded insects are an important fallback food.”

Previous research has shown that fallback foods help shape the evolution of primate body forms, including the development of strong jaws, thick teeth and specialized digestive systems in primates whose fallback diets rely mainly on vegetation.

This study suggests that fallback foods can also play an important role in shaping brain evolution among primates that fall back on insect-based diets, and that this influence is most pronounced among primates that evolve in habitats with wide seasonal variations, such as the wet-dry cycles found in some South American forests.

“Capuchin monkeys are excellent models for examining evolution of brain size and intelligence for their small body size, they have impressively large brains,” Melin said. “Accessing hidden and well-protected insects living in tree branches and under bark is a cognitively demanding task, but provides a high-quality reward: fat and protein, which is needed to fuel big brains.”

But when it comes to using tools, not all capuchin monkey strains and lineages are created equal, and Melin’s theories may explain why.

Perhaps the most notable difference between the robust (tufted, genus Sapajus) and gracile (untufted, genus Cebus) capuchin lineages is their variation in tool use. While Cebus monkeys are known for clever food-foraging tricks, such as banging snails or fruits against branches, they can’t hold a stick to their Sapajus cousins when it comes to the
innovative use and modification of sophisticated tools.

One explanation, Melin said, is that Cebus capuchins have historically and consistently occupied tropical rainforests, whereas the Sapajus lineage spread from their origins in the Atlantic rainforest into drier, more temperate and seasonal habitat types.

“Primates who extract foods in the most seasonal environments are expected to experience the strongest selection in the ‘sensorimotor intelligence’ domain, which includes cognition related to object handling,” Melin said. “This may explain the occurrence of tool use in some capuchin lineages, but not in others.”

Genetic analysis of mitochondial chromosomes suggests that the Sapajus-Cebus diversification occurred millions of years ago in the late Miocene epoch.

“We predict that the last common ancestor of Cebus and Sapajus had a level of SMI more closely resembling extant Cebus monkeys, and that further expansion of SMI evolved in the robust lineage to facilitate increased access to varied embedded fallback foods,
necessitated by more intense periods of fruit shortage,” she said.

One of the more compelling modern examples of this behavior, said Melin, is the seasonal consumption of termites by chimpanzees, whose use of tools to extract this protein-rich food source is an important survival technique in harsh environments.

What does this all mean for hominids?

While it’s hard to decipher the extent of seasonal dietary variations from the fossil record, stable isotope analyses indicate seasonal variation in diet for at least one South African hominin, Paranthropus robustus. Other isotopic research suggests that early human diets may have included a range of extractable foods, such as termites, plant roots and tubers.

Modern humans frequently consume insects, which are seasonally important when other animal foods are limited.

This study suggests that the ingenuity required to survive on a diet of elusive insects has been a key factor in the development of uniquely human skills:

It may well have been bugs that helped build our brains.

Monkeys also believe in winning streaks

Humans have a well-documented tendency to see winning and losing streaks in situations that, in fact, are random. But scientists disagree about whether the “hot-hand bias” is a cultural artifact picked up in childhood or a predisposition deeply ingrained in the structure of our cognitive architecture.

Now in the first study in non-human primates of this systematic error in decision making, researchers find that monkeys also share our unfounded belief in winning and losing streaks. The results suggests that the penchant to see patterns that actually don’t exist may be inherited—an evolutionary adaptation that may have provided our ancestors a selective advantage when foraging for food in the wild, according to lead author Tommy Blanchard, a doctoral candidate in brain and cognitive sciences at the University of Rochester.

The cognitive bias may be difficult to override even in situations that are truly random. This inborn tendency to feel that we are on a roll or in a slump may help explain why gambling can be so alluring and why the stock market is so prone to wild swings, said coauthor Benjamin Hayden, assistant professor brain and cognitive sciences at the University of Rochester.

Hayden, Blanchard, and Andreas Wilke, an assistant professor of psychology at Clarkson University, reported their findings in the July issue of the Journal of Experimental Psychology: Animal Learning and Cognition.

To measure whether monkeys actually believe in winning streaks, the researchers had to create a computerized game that was so captivating monkeys would want to play for hours. “Luckily, monkeys love to gamble,” said Blanchard. So the team devised a fast-paced task in which each monkey could choose right or left and receive a reward when they guessed correctly.

The researchers created three types of play, two with clear patterns (the correct answer tended to repeat on one side or to alternate from side to side) and a third in which the lucky pick was completely random. Where clear patterns existed, the three rhesus monkeys in the study quickly guessed the correct sequence. But in the random scenarios, the monkeys continued to make choices as if they expected a “streak”. In other words, even when rewards were random, the monkeys favored one side.

The monkeys showed the hot-hand bias consistently over weeks of play and an average of 1,244 trials per condition. “They had lots and lots of opportunities to get over this bias, to learn and change, and yet they continued to show the same tendency,” said Blanchard.

So why do monkeys and humans share this false belief in a run of luck even when faced over and over with evidence that the results are random? The authors speculate that the distribution of food in the wild, which is not random, may be the culprit. “If you find a nice juicy beetle on the underside of a log, this is pretty good evidence that there might be a beetle in a similar location nearby, because beetles, like most food sources, tend to live near each other,” explained Hayden.

Evolution has also primed our brains to look for patterns, added Hayden. “We have this incredible drive to see patterns in the world, and we also have this incredible drive to learn. I think it’s very related to why we like music, and why we like to do crossword puzzles, Sudoku, and things like that. If there’s a pattern there, we’re on top of it. And if there may or may not be a pattern there, that’s even more interesting.”

Understanding the hot-hand bias could inform treatment for gambling addiction and provide insights for investors, said Hayden. “If a belief in winning streaks is hardwired, then we may want to look for more rigorous retaining for individuals who cannot control their gambling. And investors should keep in mind that humans have an inherited bias to believe that if a stock goes up one day, it will continue to go up.”

The results also could provide nuance to our understanding of free will, said Blanchard, who was drawn to the study of decision making during prior graduate training in philosophy. “Biases in our decision-making mechanisms, like this bias towards belief in winning and losing streaks, say something really deep about what sorts of creatures we are. We often like to think we make decisions based only on the information we’re conscious of. But we’re not always aware of why we make certain decisions or believe certain things.

“We’re a complex mix of biases and heuristics and statistical reasoning. When you put it all together, that’s how you get sophisticated behavior. We don’t know where a lot of these biases come from, but this study—and others like it—suggest many of them are due to cognitive mechanisms we share with our primate relatives,” said Blanchard.

Exceptional Evolutionary Divergence of Human Muscle and Brain Metabolomes Parallels Human Cognitive and Physical Uniqueness

Metabolite concentrations reflect the physiological states of tissues and cells. However, the role of metabolic changes in species evolution is currently unknown. Here, we present a study of metabolome evolution conducted in three brain regions and two non-neural tissues from humans, chimpanzees, macaque monkeys, and mice based on over 10,000 hydrophilic compounds. While chimpanzee, macaque, and mouse metabolomes diverge following the genetic distances among species, we detect remarkable acceleration of metabolome evolution in human prefrontal cortex and skeletal muscle affecting neural and energy metabolism pathways. These metabolic changes could not be attributed to environmental conditions and were confirmed against the expression of their corresponding enzymes. We further conducted muscle strength tests in humans, chimpanzees, and macaques. The results suggest that, while humans are characterized by superior cognition, their muscular performance might be markedly inferior to that of chimpanzees and macaque monkeys.

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‘Free choice’ in primates can be altered through brain stimulation

When electrical pulses are applied to the ventral tegmental area of their brain, macaques presented with two images change their preference from one image to the other. The study by researchers Wim Vanduffel and John Arsenault (KU Leuven and Massachusetts General Hospital) is the first to confirm a causal link between activity in the ventral tegmental area and choice behaviour in primates.

The ventral tegmental area is located in the midbrain and helps regulate learning and reinforcement in the brain’s reward system. It produces dopamine, a neurotransmitter that plays an important role in positive feelings, such as receiving a reward. “In this way, this small area of the brain provides learning signals,” explains Professor Vanduffel. “If a reward is larger or smaller than expected, behavior is reinforced or discouraged accordingly.”

Causal link

This effect can be artificially induced: “In one experiment, we allowed macaques to choose multiple times between two images – a star or a ball, for example. This told us which of the two visual stimuli they tended to naturally prefer. In a second experiment, we stimulated the ventral tegmental area with mild electrical currents whenever they chose the initially nonpreferred image. This quickly changed their preference. We were also able to manipulate their altered preference back to the original favorite.”

The study, which will be published online in the journal Current Biology on 16 June, is the first to confirm a causal link between activity in the ventral tegmental area and choice behaviour in primates. “In scans we found that electrically stimulating this tiny brain area activated the brain’s entire reward system, just as it does spontaneously when a reward is received. This has important implications for research into disorders relating to the brain’s reward network, such as addiction or learning disabilities.”

Could this method be used in the future to manipulate our choices? “Theoretically, yes. But the ventral tegmental area is very deep in the brain. At this point, stimulating it can only be done invasively, by surgically placing electrodes – just as is currently done for deep brain stimulation to treat Parkinson’s or depression. Once non-invasive methods – light or ultrasound, for example – can be applied with a sufficiently high level of precision, they could potentially be used for correcting defects in the reward system, such as addiction and learning disabilities.”

Primates and patience — the evolutionary roots of self control

A chimpanzee will wait more than two minutes to eat six grapes, but a black lemur would rather eat two grapes now than wait any longer than 15 seconds for a bigger serving.

It’s an echo of the dilemma human beings face with a long line at a posh restaurant. How long are they willing to wait for the five-star meal? Or do they head to a greasy spoon to eat sooner?

A paper published today in the scientific journal Proceedings of the Royal Society B explores the evolutionary reasons why some primate species wait for a bigger reward, while others are more likely to grab what they can get immediately.

"Natural selection has shaped levels of patience to deal with the types of problems that animals face in the wild," said author Jeffrey R. Stevens, a comparative psychologist at the University of Nebraska-Lincoln and the study’s lead author. "Those problems are species-specific, so levels of patience are also species-specific."

Studying 13 primate species, from massive gorillas to tiny marmosets, Stevens compared species’ characteristics with their capacity for “intertemporal choice.” That’s a scientific term for what some might call patience, self-control or delayed gratification.

He found the species with bigger body mass, bigger brains, longer lifespans and larger home ranges also tend to wait longer for a bigger reward.

Chimpanzees, which typically weigh about 85 pounds, live nearly 60 years and range about 35 square miles, waited for a reward for about two minutes, the longest of any of the primate species studied. Cotton-top tamarins, which weigh less than a pound and live about 23 years, waited about eight seconds before opting for a smaller, immediate reward.

The findings are based partially on experiments Stevens performed during the past ten years with lemurs, marmosets, tamarins, chimpanzees and bonobos at Harvard’s Department of Psychology and at the Berlin and Leipzig zoos in Germany. In those experiments, individual animals chose between a tray containing two grapes that they could eat immediately and a tray containing six grapes they could eat after waiting. The wait times were gradually increased until the animal reached an “indifference point” when it opted for the smaller, immediate reward instead of waiting.

Stevens combined those results with those of scientists who performed similar experiments with other primates. He scoured primate-research literature to gather data on the biological characteristics of each species.

In addition to characteristics related to body mass, Stevens analyzed but found no correlation with two other hypotheses for patience: cognitive ability and social complexity.

"In humans, the ability to wait for delayed rewards correlates with higher performance in cognitive measures such as IQ, academic success, standardized test scores and working memory capacity," he wrote. "The cognitive ability hypothesis predicts that species with higher levels of cognition should wait longer than those with lower levels."

But Stevens found no correlation between patience levels and an animal’s relative brain size compared to its body size, the measure he used to quantify cognitive ability.

Researchers also have argued that animals in complex social groups have reduced impulsivity and more patience to adapt to the social hierarchies of dominance and submission. But Stevens did not find correlations between species’ social group sizes and their patience levels.

Stevens said he believes metabolic rates may be the driving factor connecting patience with body mass and related physical characteristics. Smaller animals tend to have higher metabolic rates.

"You need fuel and you need it at a certain rate," he said. "The faster you need it, the shorter time you will wait."

Metabolic rates also may factor in human beings’ willingness to wait. Stevens said human decisions about food, their environment, their health care and even their finances all relate to future payoffs. The mental processes behind those decisions have not yet been well identified.

"To me, this offers us interesting avenues to start thinking about what factors might influence human patience," he said. "What does natural selection tell us about decision making? That applies to humans as well as to other animals."

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Oxytocin promotes social behavior in infant rhesus monkeys

The hormone oxytocin appears to increase social behaviors in newborn rhesus monkeys, according to a study by researchers at the National Institutes of Health, the University of Parma in Italy, and the University of Massachusetts, Amherst. The findings indicate that oxytocin is a promising candidate for new treatments for developmental disorders affecting social skills and bonding.

Oxytocin, a hormone produced by the pituitary gland, is involved in labor and birth and in the production of breast milk. Studies have shown that oxytocin also plays a role in parental bonding, mating, and in social dynamics. Because of its possible involvement in social encounters, many researchers have suggested that oxytocin might be useful as a treatment for conditions affecting social behaviors, such as autism spectrum disorders. Although oxytocin has been shown to increase certain social behaviors in adults, before the current study it had not been shown to do so in primate infants of any species.

Working with infant rhesus monkeys, the NIH researchers found that oxytocin increased two facial gestures associated with social interactions— one used by the monkeys themselves in certain social situations, the other in imitation of their human caregivers.

“It was important to test whether oxytocin would promote social behaviors in infants in the same respects as it appears to promote social interaction among adults,” said the study’s first author, Elizabeth A. Simpson, Ph.D., postdoctoral fellow of the University of Parma, conducting research in the Comparative Behavioral Genetics Section of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “Our results indicate that oxytocin is a candidate for further studies on treating developmental disorders of social functioning.”

The study was published online in Proceedings of the National Academy of Sciences.

The researchers began by gauging the ability of rhesus macaques to imitate two facial gestures: lip smacking and tongue protrusion. In lip smacking, the lips are protruded and open, then smacked together repeatedly. The study authors wrote that rhesus mothers will engage in this facial gesture with their infants in the first month after giving birth. Tongue protrusion involves a brief protrusion and retraction of the tongue. Although this gesture is seen in other primates and typically not seen in macaques, macaques will imitate it when their human caregivers display it, the study authors added.

By observing the monkeys’ ability to imitate the two gestures, the researchers sought to determine if oxytocin could promote social interaction through a gesture that was natural to them as well as through a gesture not part of their normal communication sequence.

The researchers tested the infants in the first week after birth. Three times a day, every other day, the caregivers would demonstrate the facial gestures in sequence to the infant monkeys, while the animals’ responses were recorded on video. At this phase of the study, the researchers found that some of the monkeys mimicked their caregivers’ gestures more frequently than did other monkeys. The researchers referred to the monkeys who gestured more frequently as strong imitators.

Beginning in the second week of life, the researchers tested the monkeys on two separate days. The infant monkeys inhaled an aerosolized dose of oxytocin in one session, and a dose of saline in the other. In each session, the dose was delivered through an inhalation mask held gently over the animal’s face.

Overall, the monkeys were more communicative after receiving oxytocin, more frequently making facial gestures, than they were after receiving the saline. The monkeys were more likely to engage in lip smacking than tongue protrusion, but were more likely still to engage in either of these gestures after oxytocin than after the saline. There also were differences in the frequency of gesturing among the individual monkeys, with the strong imitators becoming even stronger imitators after receiving oxytocin.

After oxytocin exposure, the strong imitators were more likely to look at caregivers and stand close to them than they were after the saline. Looking into a caregiver’s face and remaining in close proximity to a caregiver are indicators of social interaction and social interest, Dr. Simpson said.

In another test, the researchers found that after exposure to oxytocin, monkeys had lower levels of cortisol in their saliva. Cortisol is produced by the adrenal glands in response to stress. Lower cortisol levels after oxytocin exposure indicate that oxytocin may also function to diminish anxiety, the researchers wrote.