Primate Behavior May Reveal Clues to Evolution of Favor Exchange in Humans

When your neighbor asks to borrow a cup of sugar and you readily comply, is your positive response a function of the give and take that characterize your longstanding relationship? Or does it represent payment –– or prepayment –– for the cup of sugar you borrowed last week, or may need to borrow a month from now?

Adrian Jaeggi, a postdoctoral researcher in anthropology at UC Santa Barbara, and a junior research fellow at the campus’s SAGE Center for the Study of the Mind, is studying this question of reciprocity, using chimpanzees and bonobos as his test subjects. His findings appear in the current online issue of the journal Evolution & Human Behavior.

"The article focuses on the question of whether individuals do favors because they expect them to be reciprocated at some other time, and, more specifically, whether such exchanges have to happen immediately, or can take place over longer time spans," Jaeggi explained. "We studied the question in chimpanzees and bonobos –– our two closest living relatives –– and looked at the exchanges of grooming and food sharing, which are two common types of favors among these apes."

According to Jaeggi, while results of his research provide some evidence for immediate exchanges, they more strongly support the notion that favors are exchanged over long periods of time. Calculated exchanges, in which individuals keep a detailed score of past interactions, are much less common than the more loosely balanced exchanges that take place in stable relationships.

Optical Illusions Show How We See

Imagine… as you wake later than usual rolling over towards the window, you notice that it’s a gorgeous day outside. Warm, yellow sunlight shines in through glass illuminating floating “dust angles.” On the other side of the glass, past the oak tree with yellowing leaves, you see a brilliant blue sky. For the first time it occurs to you that a blue sky is a contradiction: the sky at night is devoid of color, so why during the day does the world seem to be shrouded in a blanket of blue? Years previously as a child full of questions you asked your parents, but the answer they offered seemed somehow inadequate at the time… less than magical. And so the question remains… as it does the most of us.

The answer is this: The sky isn’t actually colored at all (not blue or yellow or red or green). Rather, it’s your mind that’s colored. The world around us is physics devoid of meaning, whereas our perception of the world is meaning devoid of physics. In terms of physics, the light in the sky is heavily biased towards smaller wavelengths (around 450 nanometers). This is because the air itself scatters smaller wavelengths of light more than it does larger ones. Which means the air in the sky is like a filter, letting primarily medium to long wavelengths through more easily than short wavelengths. Hence why the sky is composed primarily of shorter wavelengths (and so appears bluish), whereas the light from sun is composed primarily of longer wavelengths (and so appears more reddish). While the differential scattering of sunlight by the air explains the non-uniform distribution of wavelengths across the sky, it doesn’t explain why shorter wavelengths are seen as blue and the longer ones as red.

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Great apes go through mid-life crisis

They may not take up surfing or start second careers as cupcake-makers, but chimpanzees and orangutans seem to go through a ‘mid-life crisis’, just like humans.

A study of 508 great apes in captivity shows that the animals’ sense of well-being bottoms out in their late 20s to mid-30s, the ape equivalent of middle age, before rebounding in old age.

The finding that mid-life crises may not be uniquely human suggests that the events might have a biological, rather than a sociological, cause.

Men and women worldwide, regardless of their wealth or status, experience a dip in happiness at middle-age, generally defined as from the mid-30s to late 50s. Despite this universality, social scientists have struggled to identify the underlying cause of the dissatisfaction. Social and economic factors, such as financial hardship and the failure to realize unrealistic ambitions, are possible causes.

Alexander Weiss, a psychologist at the University of Edinburgh, UK, and his team set out to see if there might be a biological factor involved in the crises. They sought to assess the well-being of captive chimpanzees and orangutans as judged by their keepers or those who knew them well.

The apes covered all age ranges, and their ‘happiness’ was rated through a survey answered by their keepers. The survey covered four criteria: the animals’ overall mood; how much pleasure they got out of socializing; their success in achieving goals such as obtaining food and objects they desire; and how happy the keeper would be if he or she were that animal for a week.

The survey is admittedly anthropomorphic, says Weiss, but he adds that it is easy for someone who spends a lot of time with an ape to gauge its mood. Moreover, his previous work shows that the measure of well-being is consistent when measured by different caretakers, and is based, in part, on inherited genetic factors.

Among three different groups of chimps and orangutans surveyed, the happiest tended to be the oldest and youngest, and the most dissatisfied tended to be in their 30s. The study, however, is a snapshot — it didn’t follow any of the apes over time — which means there could be confounding factors such as the early death of unhappy apes. Nonetheless, Weiss believes the results offer a true picture.

It Just Smells

If you play sounds of many different frequencies at the same time, they combine to produce neutral “white noise.” Neuroscientists say they have created an analogous generic scent by blending odors. Such “olfactory white” might rarely, if ever, be found in nature, but it could prove useful in research, other scientists say.

Using just a few hundred types of biochemical receptors, each of which respond to just a few odorants, the human nose can distinguish thousands of different odors. Yet humans can’t easily identify the individual components of a mixture, even when they can identify the odors alone, says Noam Sobel, a neuroscientist at the Weizmann Institute of Science in Rehovot, Israel. Now, he and his colleagues suggest, various blends made up of a large number of odors all begin to smell the same—even when the blends share no common components.

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Although many scents—such as coffee, wine, roses, and dirty socks—are complex blends containing hundreds of components, they are very distinctive. At least two factors are responsible, Sobel says: The individual odorants are often chemically related, and often one or more of them is vastly more intense than the rest.

The team’s findings are “a clever piece of work that shows the olfactory system works exactly as we would predict from our current understanding of it,” says Tim Jacob, a neuroscientist at Cardiff University in the United Kingdom. “That is, if you stimulate every olfactory ‘channel’ to the same extent, the brain cannot characterize or identify a particular smell,” he notes.

“Olfactory white is a neat idea, and it draws interesting parallels to white light and white noise,” says Jay Gottfried, an olfactory neuroscientist at Northwestern University’s Feinberg School of Medicine in Chicago, Illinois. The new study “definitely adds new information about how the brain interprets odors,” he notes.

Even though olfactory white is not likely to be encountered in nature, the concept could be useful, Gottfried says. “Researchers have found that white noise is a useful stimulus in experiments to probe auditory responses,” he notes, and scientists probing the human sense of smell might find similar uses for olfactory white.

The Hazards of Growing Up Painlessly

The girl who feels no pain was in the kitchen, stirring ramen noodles, when the spoon slipped from her hand and dropped into the pot of boiling water. It was a school night; the TV was on in the living room, and her mother was folding clothes on the couch. Without thinking, Ashlyn Blocker reached her right hand in to retrieve the spoon, then took her hand out of the water and stood looking at it under the oven light. She walked a few steps to the sink and ran cold water over all her faded white scars, then called to her mother, “I just put my fingers in!” Her mother, Tara Blocker, dropped the clothes and rushed to her daughter’s side. “Oh, my lord!” she said — after 13 years, that same old fear — and then she got some ice and gently pressed it against her daughter’s hand, relieved that the burn wasn’t worse.

“I showed her how to get another utensil and fish the spoon out,” Tara said with a weary laugh when she recounted the story to me two months later. “Another thing,” she said, “she’s starting to use flat irons for her hair, and those things get superhot.”

Tara was sitting on the couch in a T-shirt printed with the words “Camp Painless But Hopeful.” Ashlyn was curled on the living-room carpet crocheting a purse from one of the skeins of yarn she keeps piled in her room. Her 10-year-old sister, Tristen, was in the leather recliner, asleep on top of their father, John Blocker, who stretched out there after work and was slowly falling asleep, too. The house smelled of the homemade macaroni and cheese they were going to have for dinner. A South Georgia rainstorm drummed the gutters, and lightning illuminated the batting cage and the pool in the backyard.

Without lifting her eyes from the crochet hooks in her hands, Ashlyn spoke up to add one detail to her mother’s story. “I was just thinking, What did I just do?” she said.

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Virtual Reality Could Spot Real-World Impairments

A virtual reality test being developed at UTSC might do a better job than pencil-and-paper tests of predicting whether a cognitive impairment will have real-world consequences.

The test developed by Konstantine Zakzanis, associate professor of psychology, and colleagues, uses a computer-game-like virtual world and asks volunteers to navigate their ways through tasks such as delivering packages or running errands around town.

“If we’re being asked to tell if people could do things like work, houseclean, and take care of their kids, we need to show that our tests predict performance in the real world,” says Zakzanis.

But standard tests don’t do that very well, he says. Although tests that ask people to do things like solve math problems, sort cards, remember names, or judge the relative positions of lines in visual two dimensional space, can detect cognitive impairments caused by circumscribed lesions following a stroke or head injury, they’re not very good at predicting who will be able to function in the real world and who won’t.

That’s a problem for cognitively impaired people who might be denied insurance benefits or workers compensation based on tests that are insensitive to demonstrating their impairment. It is akin to having a broken arm with no x-ray to prove it.

Linguistics as a Window to Understanding the Brain