Newborn babies have a preference for the way living things move

Blogging on Peer-Reviewed ResearchFrom an animal’s point of view, the most important things in the world around it are arguably other animals. They provide mates, food, danger and companionship, so as an animal gazes upon its surroundings, it pays for it to be able to accurately discern the movements of other animals. Humans are no exception and new research shows that we are so attuned to biological motion that babies just two days old are drawn to extremely simple abstract animations of walking animals.

Running animal Animals move with a restrained fluidity that makes them stand out from inanimate objects. Compared to a speeding train or a falling pencil, animals show far greater flexibility of movement but most are nonetheless constrained by some form of rigid skeleton. That gives our visual system something to latch on to.

In 1973, Swedish scientist Gunnar Johansson demonstrated this to great effect by showing that a few points of light placed at the joints of a moving animal to simulate its gait. When we see these sparse animations, we see them for what they represent almost instantaneously.

Don’t believe me? Just look at this human walker from Nikolaus Troje’s BioMotion Lab website. With just fifteen white dots, you can not only simulate a walking adult, but you can also tell if it’s male or female, happy or sad, nervous or relaxed. Movement is the key to the illusion – any single static frame merely looks like a random collection of unconnected dots. But once they start to move in time, the brain performs an amazing feat of processing that extract the image of a human from the random dots.

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Short lives, short size – why are pygmies small?

Blogging on Peer-Reviewed ResearchBaka pygmiesFor decades, anthropologists have debated over why pygmies have evolved to be short. Amid theories about their jungle homes and lack of food, new research suggests that we have been looking at the problem from the wrong angle. The diminutive stature of pygmies is not a direct adaptation to their environment, but the side-effect of an evolutionary push to start having children earlier.

Andrea Migliano at the University of Cambridge suggests that pygmies have opted for a ‘live fast, die short’ strategy. Their short lives gives them very limited time as potential parents, and they have adapted by becoming sexually mature at a young age. That puts a brake on their pubescent growth spurts, leaving them with shorter adult heights.

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Subliminal flag shifts political views and voting choices

Blogging on Peer-Reviewed ResearchSubliminal flag shifts political views and voting choicesFor all the millions that are poured into electoral campaigns, a voter’s choice can be influenced by the subtlest of signals. Israeli scientists have found that even subliminal exposure to national flags can shift a person’s political views and even who they vote for. They managed to affect the attitudes of volunteers to the Israeli-Palestine conflict by showing them the Israeli flag for just 16 thousandths of a second, barely long enough for the image to consciously register.

These results are stunning – even for people right in the middle of the one of the modern age’s most deep-rooted conflicts, the subconscious sight of a flag drew their sympathies towards the political centre.

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Genes affect our likelihood to punish unfair play

As a species, we value fair play. We’re like it so much that we’re willing to eschew material gains in order to punish cheaters who behave unjustly. Psychological games have set these maxims in stone, but new research shows us for the first time, that this sense of justice is, to a large extent, influenced by our genes.

When it comes to demonstating our innate preference for fair play, psychologists turn to the ‘Ultimatum Game‘, where two players bargain over a pot of money. The ‘proposer’ suggests how the money should be divided and the ‘receiver’ can accept of refuse the deal. If they refuse, neither player gets anything and there is no room for negotiation. In a completely rational setting, the proposer should offer the receiver as little as possible, and the receiver should take it – after all, a very little money is better than none at all.

Of course, that’s not what happens. Receivers typically abhor unfair offers and would rather that both parties receive no money than accept a patronisingly tiny amount. Across most Western countries, proposers usually offer the receivers something between 40% and 50% of the takings. Any offers under 10% are almost always rejected.

The uniformity of responses across Western countries suggests that culture has a strong effect on how people play the game, but until now, no one had looked to see how strongly genes asserted their influence. Bjorn Wallace and colleagues from the Stockholm School of Economics decided to do just that, and they used the classic experiment for working out heritability – the twin study.

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Predicting ethnic violence – why good neighbours need good fences

Everybody, apparently, needs good neighbours, but in many parts of the world, your neighbours can be your worst enemy. In the past century, more than 100 million people have lost their lives to violent conflicts. Most of these were fought between groups of people living physically side by side, but separated by culture or ethnicity.

Good fences make good neighboursNow, May Lim and colleagues from the New England Complex Systems Institute have developed a mathematical model that can predict where such conflicts by looking at how different groups are spread out in a given area.

According to their research, violence is most likely to erupt in areas with poorly-defined boundaries between large and culturally different groups. Their model predicted areas of ethnic violence in both India and Yugoslavia with uncanny accuracy, and Lim hopes that it will help policymakers to look at the problem of violent conflicts with a scientific eye.

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The fall and rise of lefties in Victorian England

Left-handers were less common in Victorian EnglandAbout 11% of the British population is currently left-handed. But that wasn’t always the case. Among people born in 1900, the proportion of lefties was just 3%.

Chris McManus and Alex Hartigan from University College London worked this out with the help of old films made at the turn of the 19th century and recently restored. The films, which show people moving in and out of Victorian factories, paint an evocative picture of a time gone by. By noting which hand the people in the film waved in, the duo were able to work out the proportions of left-handers alive at the time.

I interviewed McManus last week about his study, London and his writing as my first proper freelance writing assignment. He had lots to say and said it very well. Have a look at the full interview at Nature Networks.

More on asymmetry:

Asymmetrical brains help us (and fish) to multi-task

Reference: McManus & Hartigan. 2007. Declining left-handedness in Victorian England seen in the films of Mitchell and Kenyon. Curr Biol 17: R793-R794.

Virtual reality illusions produce out-of-body experiences in the lab

Using virtual reality illusions, two groups of scientists have managed to simulate out-of-body experiences in the lab – by convincing volunteers that they were actually sitting or standing outside of their own bodies, watching themselves from behind. These studies can tell us a lot about our own self-consciousness.

The idea of an out-of-body experiences seems strange and hokey – certainly not one that would grace one of the world’s top scientific journals. So it may seem surprising it cropped up in not one, but two papers in Science this week.

Out-of-body experiences are rooted in malfunctioning brain mechanismsOut-of-body experiences are rare and can be caused by epileptic fits, neurological conditions such as strokes and heavy drug abuse. Clearly, they are triggered when something goes wrong in our brains. And as usual for the brain, something going wrong can tell us a lot about what happens the rest of the time.

Simply put, if we very rarely have an out-of-body experience, why is it that for the most part we have ‘in-body’ experiences? It’s such a fundamental part of our lives that we often take it for granted, but there must be some mental process that ensures that our perceptions of ‘self’ are confined to our own bodies. What is it?

Two groups of scientists have taken steps to answering these questions using illusion and deception. They managed to experimentally induce mild out-of-body experiences in healthy volunteers, by using virtual reality headsets to fool people into projecting themselves into a virtual body.

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Five-month-old babies prefer their own languages and shun foreign accents

Discriminating against people who do not speak your language is a big problem. A new study suggests that the preferences that lead to these problems are hard-wired at a very young age. Even five-month-old infants, who can’t speak themselves, have preferences for native speakers and native accents.

The human talent for language is one of our crowning evolutionary achievements, allowing us to easily and accurately communicate with our fellows. But as the Biblical story of the Tower of Babel relates, linguistic differences can serve to drive us apart and act as massive barriers between different social groups.

The Tower of Babel story highlights the conflicts that can arise when people don’t speak the same language.These barriers can give rise to linguistic discrimination, a far more insidious problem that it seems at first. Language-based prejudices have led to horrific acts of human abuse, and even civil wars. Genocide often finds itself paired with linguicide, since a race can be killed off more thoroughly if their language follows them.

Even today, people in a linguistic minority can find themselves denied access to healthcare, or at a disadvantage when looking for jobs. The issue cuts to the heart of several ongoing debates, from the role of second languages in education to whether immigrants must become fluent in the tongue of their host country.

Early preferences

It should therefore be unsurprising to learn that we have strong preferences for our own language and for those who speak it. But Katherine Kinzler and colleagues from Harvard University, have found that we develop these preferences from an incredibly young age, before we can speak ourselves, and well before we can even hope to understand the social issues at stake.

Kinzler tested 24 infants, aged 5 to 6 months, from households that only spoke English, to see if they had any linguistic preferences. Each toddler watched videos of two women, one speaking English and the other, Spanish. The women were all bilinguals and swapped the language they used in different trials to make sure that the babies weren’t showing preferences for physical traits like skin colour.

The babies were then shown the two women side by side, but no longer speaking. They strongly expressed their preference for the English speakers by gazing at their screen for a longer time (measuring gaze time like this is a standard test used by child psychologists).

Once developed in early infancy, these preferences stick around into childhood, and most probably well beyond that. In very similar experiments, Kinzler found that older infants (10 months or so) prefer to accept toys from a woman who spoke their native language.

Even young infants can discriminate between their language and others.The babies, from either Boston or Paris, were shown alternating films of an English or French-speaking woman, who spoke for a while and then silently offered the child a toy. Two real toys then appeared on the table in front of the infant, and they were twice as likely to pick the one in front of the native speaker.

So even though the offering of the toy involved no spoken words, the infants still gravitated towards the woman who had spoken earlier in their familiar tongue.

Different accents

Infants can even pick up on subtle differences in dialect. Even when two speakers are talking in the same language, 5-month old infants will prefer someone who speaks with a native accent to someone who speaks with a foreign twang. Older children (5 years or so) will similarly prefer to befriend another child who speaks with the same accent.

At that age, children will have barely any understanding of the social circumstances that leads to different groups of people speaking the same language in different ways. And it’s unlikely that their parents had much influences, since even the 5-month-old toddlers had these preferences.

These early preferences can act as the foundations for more destructive behaviours and conflicts later on in life. But we must be very careful – an instinctive basis for a behaviour does not in any way justify it.

Instead, by telling us about the basis of linguistic prejudices, these results suggest that we must work even harder to overcome them. If they are hard-wired from an early age, then education from an early age seems like a sensible first step.

Perhaps, exposure to multiple languages early in life can soften these preferences, and it would be fascinating to see if the same results hold for babies from bilingual households.

More on languages, child development, and social conflicts:
Babies can tell apart different languages with visual cues alone
Experience tunes a part of the brain to the shapes of words
In conflicts over beliefs and values, symbolic gestures matter more than reason or money

Reference: Kinzler, Dupoux & Spelke. 2007. The native language of social cognition. PNAS 104: 12577-12580

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Altruistic chimpanzees clearly help each other out

Many scientists have argued that only humans show true altruistic behaviour. But a group of Ugandan chimps is set to change all that by showing clear signs of true selflessness, helping other unrelated chimps with no desire for reward.

Why do we help each other, instead of constantly looking out for ourselves? This is one of the most compelling questions in modern biology. Evolutionary and game theory alike predict that selfish behaviour should be the rule with altruism the exception, and animal experiments have largely supported this idea.

Nature, ‘red in tooth and claw’, is painted as a fierce competition between selfish individuals and their even more selfish genes. In this stark landscape, true altruism is a rare quality and some scientists believe that it’s one that only we humans possess.

Even our closest relatives, chimpanzees, are not exempt from this dividing line. Certainly, there is a large amount of anecdotal evidence of chimps helping each other or even saving each others’ lives. But some thinkers believe that this behaviour, along with other seemingly selfless animal acts, is actually self-serving in one of two ways.

The chimps could be helping their relatives in order to advanced the spread of its own genes, which family members are likely to share. Or they could be doing a favour for another individual, in the knowledge that it will be repaid later on. Either way, it’s the do-gooder that eventually benefits.

Humans, on the other hand, seem to flaunt this rule. We often help others who are not relatives and who are unlikely to repay the favour. We go out of our way to be helpful, and sometimes even risk personal harm to do so.

Two tests for altruism

Now, Felix Warneken and colleagues form the Max Planck Institute for Evolutionary Anthropology have found compelling evidence that we are not alone. Contrary to previous studies, they have found that chimps also behave altruistically in a very human way. They help out unrelated strangers without expectation of reward, and even go to great lengths to do so.

Warneken studied 36 chimps at Ngamba Island Chimpanzee Sanctuary, Uganda and looked at their willingness to help a human handler. To minimise the effect of any human-chimp bond, he only looked at chimps that were born in the wild, and used experimenters who the chimps had never seen before.

In the first test, the chimps saw a human unsuccessfully trying to reach a stick that they themselves could reach. Warneken found that chimps were all too happy to pass the stick across (video), regardless of whether they were rewarded with a banana or not. In fact, the only thing that affected their readiness to lend a hand was whether the human was struggling for the stick or just passively staring at it.

He found the same thing when he ran a similar set-up with a 36 eighteen-month-old human toddlers, but with toy cubes in lieu of sticks (video). At that age, a baby’s mental abilities are thought to similar to those of chimps, and indeed the only real difference between the two was that the babies were quicker with their assistance.

Passing a stick across is obviously fairly easy but would altruism persist if there was effort involved? Warneken tested this by changing the experiment so that the chimps had to climb over a raceway (video) and the toddlers had to walk past a series of obstacles (video). Those that helped in the first test were happy to do so in the second, again without any rewards.

The third and most important test

A skeptic might argue that this doesn’t show anything. During their stay at the sanctuary, the chimps could have learned that helping any one of their strange two-legged keepers was worth it. The acid test then, was to see if the chimps would help each other.

The first chimp – the subject – could only get into a room with food by lifting the chain attached to its door. But it couldn’t reach the chain – only a second chimp, the observer, could do that. And once again, the chimps proved their selflessness, lifting the chain for their fellow chimps the vast majority of the time (video).

This striking result flies in the face of other studies, which have failed to find altruistic behaviour between chimps. But in a related commentary, Frans de Waal, an international expert of ape behaviour, claimed that these were more tests of generosity than selfishness.

They created specific situations where chimps were motivated to look out for themselves and the species can’t be judged on these scenarios alone. It would be like claiming that all people are selfish after watching the self-interested behaviour of commuters. Failing to show altruism is not the same as proving that it doesn’t happen.

But it does happen – Warneken’s experiments are striking indicators of that. In the third test, the chimps were unrelated, the observer had no chance of getting a share of the food, and their roles were never reversed so there were no opportunities for payback. Clearly, humans are not alone in our desire to help each other. Chimps are now our fellows in altruism and it’s likely that our common ancestor did the same.

What this means for the altruism debate

It’s particularly fascinating that rewards in the first two tests didn’t affect the chimps’ behaviour. This suggests that chimps don’t continually analyse the pros and cons of helping their fellow – if they did, the reward would have motivated them to help even more often.

Instead, de Waal believes that the chimps have evolved psychological systems that steer them towards selflessness. In essence, natural selection has done the analysis for them and decided that altruistic behaviour works to its advantage in the long run. Selfless behaviour then, can evolve for selfish reasons, and that strikes to the very core of the debate on altruism.

Spend enough time reading about this field of research, and you could be forgiven for thinking that some scientists are taking cynical glee at ‘explaining away’ altruism. The extreme reductionist view is that discovering the evolutionary origins of selfless behaviour discredits that behaviour, somehow making it less worthy. As Robert Trivers put it, these models are designed to “take the altruism out of altruism”.

But this viewpoint is blinkered and too focused on the past. Evolutionary explanations can help us understand where an unusual behaviour like selflessness comes from, but they do not alter the value of those behaviours. They can tell us about how a behaviour arose, but not about an animal’s reasons for behaving in that way here and now.

Take sex. Its adaptive benefits are clear – it continues the line and promotes genetic diversity. But animals don’t consider the issue of reproduction every time they have sex and for the most part, humans actively deny it!

According to de Waal, we should now turn our attention to the psychological processes that foster altruism in chimps, and how they are different from those that work in our own minds. Do chimps share our strong sense of empathy, that fuels selflessness by letting us identify with the emotions and needs of others. Do their cultures, like ours, punish and vilify selfish behaviour?

References: Warneken, Hare, Melis, Hanus & Tomasello. 2007. Spontaneous altruism by chimpanzees and young children. PLOS Biology 5: e184.
de Waal. 2007. With a little help from a friend. PLOS Biology 5: e190.

Related posts on chimps:
Chimps show that actions spoke louder than words in language evolution
Not so unique – the chimpanzee Stone Age, and our place among intelligent animals
Cultured chimps pass on new traditions between groups
Chimpanzees make spears to hunt bushbabies

Related posts on altruism:
Army ants plug potholes with their own bodies

Images: from BBC, Nature, Jane Goodall Institute and Ngamba Sanctuary

Orang-utan study suggests that upright walking may have started in the trees

A common theory of human evolution says that after our ancestors descended from the trees, they went form walking on four legs to two. But a new study in orang-utans could overturn that theory, by suggesting that our ancestors evolved a bipedal walk while they were still in the trees.

Did and upright posture evolve in a tree-dwelling ancestor?Walking on two legs, or bipedalism, immediately sets us apart form other apes. It frees our arms for using tools and weapons and is a key part of our evolutionary success. Scientists have put forward a few theories to explain how our upright gait evolved, but the ‘savannah theory’ is by far the most prolific.

It’s nicely illustrated by this misleading image that has become a mainstay of popular culture. It suggests that our ancestors went from four legs to two via the four-legged knuckle-walking gait of gorillas and chimps. Dwindling forests eventually pushed them from knuckle-walking to a full upright posture. This stance is more efficient over long distances and allowed our ancestors to travel across open savannahs.

But this theory fails in the light of new fossils which push back the first appearance of bipedalism to a time before the forests thinned, and even before our ancestors split from those of chimpanzees. Very early hominins, including Lucy (Australopithecus afarensis) and Millennium Man (Orrorin) certainly ambled along on two legs, but they did so through woodland not plains.

Our arms provide a further clue. Even though our ancestors’ back legs quickly picked up adaptations for bipedalism, they steadfastly kept long, grasping arms, an adaptation more suited to moving through branches. To Susannah Thorpe at the University of Birmingham, these are signs that bipedalism evolved while our ancestors were still living in trees.

Two legs good, four legs bad?

Orang-utans can go bipedal and our ancestors may well have done the same in the trees.But there is a snag – an adaptation must provide some sort of benefit. And, as many children painfully discover, it is hard to imagine how walking on two legs could benefit sometime in a tree.

But Thorpe has an answer to this too. She spent a year in the Sumatran jungle, studying the orang-utan – the only great ape to spend the majority of its life in the trees.

She carefully documented over 3,000 sightings of wild orang-utans moving through the treetops. On large sturdy branches, they walk on all fours (below right), and on medium-sized ones, they start to use their arms to support their weight.

But on the thinnest and most unstable branches, the apes use a posture that Thorpe calls ‘assisted bipedalism’ (below left). They grip multiple branches with their long, prehensile toes and use their arms to balance and transfer their weight. And unlike chimps which bend their knees while standing up, bipedal orang-utans keep their legs straight, just like humans do.

An orang-utan used both two-legged and four-legged postures.

It’s a win-win posture – the hands provide extra safety, while the two-legged stance frees at least one hand to grab food or extra support. With it, the apes can venture onto the furthest and thinnest branches, which provides them with several advantages.

As Thorpe says, “Bipedalism is used to navigate the smallest branches where the tastiest fruits are, and also to reach further to help cross gaps between trees.” That saves them energy because they don’t have to circle around any gaps, and it saves their lives because they don’t have to descend to the ground. “The Sumatran tiger is down there licking its lips”, she said.

A new view of ape & human evolution

With these strong adaptive benefits, it becomes reasonable to suggest that bipedalism evolved among the branches. Based on this theory, Thorpe, along with Roger Holder and Robin Crompton from the University of Liverpool, have painted an intriguing new picture of ape evolution.

It begins in the same way as many others – with the rainforests of the Miocene epoch (24 to 5 million years ago) becoming increasingly patchy. For tree-dwelling apes, the gaps in the canopy started becoming too big to cross. But in Thorpe’s view, these ancestral apes were already using a bipedal stance, and different groups took it in separate directions.

Our ancestors were bipedal long before they came down from the trees.The ancestors of orang-utans remained in the increasingly fragmented canopy and became specialised and restricted there. The ancestors of chimps and those of gorillas specialised in climbing up and down trees to make use of food both in the canopy and on the ground. The postures used in vertical climbing are actually very similar to those used in four-legged knuckle-walking and this became their walk of choice on the ground.

The ancestors of humans abandoned the trees altogether. They used the bipedal stance that served them well on thin branches to exploit the potential of the stable land environment. Over time, they brought in further adaptations for efficient walking, culminating in the human walking style that we now neglect by sitting at a computer all day.

Thorpe’s reconstruction is delightfully non-human-centric. It suggests that in the evolution of movement, we were conservatives who relied on a walk that had been around for millions of years. Chimps and gorillas with their fancy new knuckle-dragging gait were the true innovators.

Reference: Thorpe, Holder & Crompton. 2007. Origin of human bipedalism as an adaptation for locomotion on flexible branches. Science 316: 1328-1331.

Image: Black and white image from Science magazine.

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Related stuff:
On ape and human evolution:
Chimps show that actions spoke louder than words in language evolution
Hidden ‘junk’ gene separates human brains from chimpanzees
Chimps have more adaptive genetic changes than humans

On the evolution of movement:
Salamander robot walks, swims and sheds light on evolutionary step from sea to land
Microraptor – the dinosaur that flew like a biplane

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Why music sounds right – the hidden tones in our own speech

The keys on a piano are a physical representation of the sounds of our speech.Have you ever looked at a piano keyboard and wondered why the notes of an octave were divided up into seven white keys and five black ones? After all, the sounds that lie between one C and another form a continuous range of frequencies. And yet, throughout history and across different cultures, we have consistently divided them into these set of twelve semi-tones.

Now, Deborah Ross and colleagues from Duke University have found the answer. These musical intervals actually reflect the sounds of our own speech, and are hidden in the vowels we use. Musical scales just sound right because they match the frequency ratios that our brains are primed to detect.

Interlude – speaking for beginners

When you talk, your larynx produces sound waves which resonate through your throats. The rest of your vocal tract –your lips, tongue, mouth and more – act as a living, flexible organ pipe, that shifts in shape to change the characteristics of these waves.

What eventually escapes from our mouths is a combination of sound waves travelling at different frequencies, some louder than others. The loudest frequencies are called formants, and different vowels have different ‘formant signature’. Our brains use these to distinguish between different vowel sounds.

The first two formants, the ones with the lowest frequencies, are the most important. The brain pays particularly close attention to these and uses them to identify vowels. If they are artificially removed from a recording, the speaker becomes impossible to understand. On the other hand, getting rid of the higher formants does no such thing.

(This spectrogram shows the different frequencies that make up three different vowels. Frequency goes up the vertical axis. The darker the image, the louder that particular frequency is. For each vowel, the first two formants (the lowest dark bands) are marked.)

A spectrogram showing formants for three common vowels.

Despite the wide variety of sounds in different languages, and the even greater variety in people’s voices, the formants of their vowels fall into narrow and defined ranges of frequencies. The first one always has a frequency of 200-1,000 Hz, while the second always lies between 800 and 3,000 Hz.

Hidden musical intervals

Ross analysed the formants of English vowels by asking 10 English speakers to read out thousands of different words and some longer monologues. Amazingly, she found that the ratio of the first two formants in English vowels tends to fall within one of the intervals of the chromatic scale.

When people say the ‘o’ sound in rod, the ratio between the first two formants corresponds to a major sixth – the interval between C and A. When they say the ‘oo’ sound in booed, the ratio matches a major third – the gap between C and E. Ross found that every two in three vowel sounds contain a hidden musical interval.

Her results didn’t just apply to English either. Ross repeated her experiments with people who spoke Mandarin, a vastly different language where speakers use four different tones to change the meaning of each word.

Even so, Ross still found musical intervals within the formant ratios of Mandarin vowels. The distribution of the ratios was even similar – in both languages, an octave gap was most common, while minor sixth was fairly uncommon.

How hidden intervals shape our musical tastes

Music sounds right to us because intervals match the frequency ratios of our vowels.Ross believes that these hidden intervals could explain many musical curiosities. For example, the musical preferences of a certain culture could reflect the formants most commonly used in its language.

Hardly any music uses the full complement of 12 semitones, and European music usually limits itself to just 7 – the so-called ‘diatonic scale’ represented by a piano’s white keys. Music from other parts of the world tends to use the ‘pentatonic scale’ where the octave is split into just 5 tones.

Ross found that the 70% of the chromatic intervals in her data were included in the diatonic scale, and 80% were found in the pentatonic one. She reckons that these scales are so widely used because they reflect the most common formant combinations in our speech.

She now wants to see if the link between formants and intervals can explain why music in a major key instinctively sounds happier and more upbeat than music in a minor key.

Formants are common to the vast majority of languages and cultures, which explains why the twelve-semitone chromatic scale is so universal. Regardless of our cultural differences, it is heartening to realise that in some ways, we are all the same.

Reference: Ross, Choi and Purves. 2007. Musical intervals in sounds. PNAS 104: 9852-9857.

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Related posts on how our minds work:

Babies can tell apart different languages with visual cues alone
Experience tunes a part of the brain to the shapes of words

Babies can tell apart different languages with visual cues alone

Most of us could easily distinguish between spoken English and French. But could you tell the difference between an English and a French speaker just by looking at the movements of their lips? It seems like a difficult task. But surprising new evidence suggest that babies can meet this challenge at just a few months of age.

The shapes of our mouths when we speak provide valuable clues that we can use to understand language.Young infants can certainly tell the difference between the sounds of different languages. Whitney Weikum and colleagues from the University of British Columbia decided to test their powers of visual discrimination.

They showed 36 English babies silent video clips of bilingual French-English speakers reading out the same sentence in one of the two languages. When they babies had become accustomed to these, Weikum showed them different clips of the same speakers reading out new sentences, some in English and some in French.

When the languages of the new sentences matched those of the old ones, the infants didn’t react unusually. But when the language was switched, they spent more time looking at the monitors. This is a classic test for child psychologists and it means that the infants saw something that drew their attention. They noticed the language change.

Weikum found that the babies have this ability at 4 and 6 months of age, but lose it by their eighth month. During the same time, other studies have found that infants become worse at telling apart consonant and vowel sounds from other languages, and even musical rhythms from other cultures.

Babies can distinguish between two languages from birth.It seems that initially, infants are sensitive to the properties of a wide range of languages. But without continuing exposure, their sensitivities soon narrow without continuing exposure to both languages, the babies’ sensitivities soon narrowed to the range that is most relevant for their mother tongue.

To test this idea, Weikum repeated his experiments on bilingual infants. Sure enough, at 8 months, these babies could still visually tell the difference between English and French speakers.

We normally think of lip-reading as a trick used only by deaf people. But this study suggests that the shapes our mouths make when we talk provide all of us with very important visual clues.

From a very early age, infants are programmed to sense these clues, and this so-called ‘visual speech’ may even help them to learn the characteristics of their native tongue.

Reference: Weikam, Vouloumanos, Navarra, Soto-Faraco, Sebastian-Galles & Werker. 2007. Visual language discrimination in infancy. Science 316: 1159.

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