Showing posts with label Evolutionary Psychology. Show all posts
Showing posts with label Evolutionary Psychology. Show all posts

March 17, 2010

700-year-old Brain Found Preserved!

ResearchBlogging.orgEvolutionary psychology tends to receive harsh criticism, and often rightly so. One of the main reasons for this is the severe lack of evidence for many of it's proposals given that the paucity of fossilised brains fails to bolster many a case. And it isn't even anyone's fault. That's just the way it goes sometimes, that the brain is a jelly-like substance that is subject to decay after death, and there's no way we can objectively analyse or verify any differences in brains of long ago with brains of today.

This isn't set to change anytime soon, but the remarkable discovery of a medieval child's brain was the subject of a Neuroimage paper published recently. This is extremely exciting on many counts: the brain has been so fantastically preserved that it is possible to identify the frontal, temporal and occipital lobes, and even the sulci and gyri, the grooves and furrows channeled into brains.



However it is only the left-hemisphere that survived and not the entire brain, which had also shrunk to about 80% of it's original weight due to the (natural) mummification process. Although it was first discovered in 1998 and preserved all this time in a formalin solution, it was found in the skull of a 13th Century infant that was exhumed at an archaeological dig in north-west France. The body of the 18-month-old child was wrapped in leather and kept in a wooden coffin with a pillow underneath the head.

The presence of acidic clay soil and fresh briny water around the burial site is believed to have contributed towards the excellent preservation of the brain. To a certain degree, even the innate cellular structure had been preserved, so much so that intact neurons and dendrites - branched fibres that extend from the cell body of a neuron - had survived for observation in the 21st Century. It was also possible to identify grey and white matter. Apart from the external burial conditions, the toughness of the neuronal myelin sheath and collagen fibres are said to be the reasons for why the brain tissue had been nicely preserved.

It cannot be said for sure how the infant died, but the presence of an unhealed circular head fracture may have been the likeliest cause. High levels of hemosiderin suggested that the infant had heavy bleeding for several days prior to death. Poor little mite.
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Papageorgopoulou, C., Rentsch, K., Raghavan, M., Hofmann, M., Colacicco, G., Gallien, V., Bianucci, R., & Rühli, F. (2010). Preservation of cell structures in a medieval infant brain: A paleohistological, paleogenetic, radiological and physico-chemical study NeuroImage, 50 (3), 893-901 DOI: 10.1016/j.neuroimage.2010.01.029

May 27, 2009

Gonna (Evolve To) Sing You My Love Song

ResearchBlogging.orgWhy do we like to sing soppy love songs to our loved one? What is it about them that evokes a mood of affinity and bonding? Why do tears spring to our eyes when we hear a lyric that reminds us of a friendship, relationship or other close bond?

The composition and interpretation of music through song, dance, and playing a musical instrument, are complex and high-level tasks of the creative brain. Indeed, the 'creative' aspects of personality are thought to constitute a particular division of intelligence in itself. Although it is possible to gain a certain level of proficiency in playing the works of Beethoven and Mozart through social and/or environmental factors (parental support, music school), the phenomenon of the child prodigy does in fact suggest an innate genetic basis for talent. Creativity itself is a complex process that draws largely from areas of the right hemisphere, not activating the frontal lobes or cortices very much. And since we are talking mainly of cognitive processes,we can expect hormones such as arginine vasopressin (AVP), which helps to control higher functions such as memory and learning, to take a lead role. Given that this hormone is mediated by the AVP receptor 1A (AVPR1A) gene, that affects many behavioural, social and emotional traits such as male aggression, pair bonding, altruism, parenting, sibling relationships, love etc., it stands to reason that this key gene is the one to watch.



A team of researchers at Helsinki University, headed by Liisa Ukkola, carried out a study purporting to investigate the neurobiological basis of music in human evolution by analysing the role of the AVPR1A gene and five others and their effects on general creativity and musical aptitude by testing 343 multigenerational participants from 19 Finnish families, professional and amateur musicians alike. Ages varied from 9 to 93 (mean age 43) and DNA was obtained by 298 (86.9%) of those over age 15. Three measures were administered: an extensive online questionnaire to assess creativity in those who composed, improvised or arranged music; Carl Seashore's pitch and time discrimination subtests (SP and ST respectively); and a Karma Music Test (KMT) designed by one of the research team. The results showed that high scores on the music tests associated well with high levels of creativity, and also higher in creative individuals than non-creative individuals. Genetic testing confirmed that creativity was a heritable trait.

Wait a minute - what does all this have to do with the brain?

This study showed how auditory structuring ability (gleaned from the KMT test) were associated with the AVPR1A gene, with the strongest effect found in the RS1+RS3 haplotype. The ST and SP tests also suggested this association, and this was further confirmed when the associations were replicated with combined music test score (COMB). The kicker is that the AVPR1A gene is instrumental in modulating social and cognitive behaviours, and music is certainly a medium that initiates, enhances and accelerates certain behaviours! We all know about the peculiar social customs of singing songs of romantic content in order to attract the opposite sex, music played to enhance group cohesion and initiate vigorous hip-spinning activity, and mothers singing soothing lullabies to their offspring in order to induce a state of quietness.

But aside from all of that, the genetic studies provided interesting tidbits of information relating to the homologies of the AVPR1A gene as various alleles were recognised to associate with either composing, arranging and performing music. Higher spatial scores were found among musicians than non-musicians, a possible explanation being that musicians tend to need to read and memorise notes and/or sheet music. Research into the recently discovered TPH2 gene may uncover the details behind the numerical sense necessary to perceive rhythm. The A1 allele associated with the dopamine receptor D2 (DRD2) gene is suggested to be linked to courtship.

The releases related to this story hyped up the evolutionary implications in a big way but I can find very little basis for that in this paper. As usual, evolutionary extrapolations are mainly speculative but interesting nevertheless. The text specifically mentions that evolutionary contributions are speculated on the basis of PET imaging that show partial overlapping between music and language-related areas of the brain. As improvising music usually consists of collaboration with other musicians or between a performer and their audience it makes sense that the role of these brain areas and the genes associated with musical talent be highlighted as it has. As the paper itself says:

"Creativity is a multifactorial genetic trait involving a complex network made up of a number of genes."
And it is because of that and the connections to social/cognitive areas of the brain that there is justification for the idea that music enables and enhances social communication in a way that increases attachments. This can explain why people automatically feel closer when they find they share the same types of music.

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Ukkola, L., Onkamo, P., Raijas, P., Karma, K., & Järvelä, I. (2009). Musical Aptitude Is Associated with AVPR1A-Haplotypes PLoS ONE, 4 (5) DOI: 10.1371/journal.pone.0005534

February 5, 2009

How Your Brain Creates God

Great article in the latest New Scientist (04 February 2009):
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Born believers: How your brain creates God

No wonder religion is so prevalent in human society – our brains are primed for it, says Michael Brooks

While many institutions collapsed during the Great Depression that began in 1929, one kind did rather well. During this leanest of times, the strictest, most authoritarian churches saw a surge in attendance.

This anomaly was documented in the early 1970s, but only now is science beginning to tell us why. It turns out that human beings have a natural inclination for religious belief, especially during hard times. Our brains effortlessly conjure up an imaginary world of spirits, gods and monsters, and the more insecure we feel, the harder it is to resist the pull of this supernatural world. It seems that our minds are finely tuned to believe in gods.

Religious ideas are common to all cultures: like language and music, they seem to be part of what it is to be human. Until recently, science has largely shied away from asking why. "It's not that religion is not important," says Paul Bloom, a psychologist at Yale University, "it's that the taboo nature of the topic has meant there has been little progress."

The origin of religious belief is something of a mystery, but in recent years scientists have started to make suggestions. One leading idea is that religion is an evolutionary adaptation that makes people more likely to survive and pass their genes onto the next generation. In this view, shared religious belief helped our ancestors form tightly knit groups that cooperated in hunting, foraging and childcare, enabling these groups to outcompete others. In this way, the theory goes, religion was selected for by evolution, and eventually permeated every human society (New Scientist, 28 January 2006, p 30) The religion-as-an-adaptation theory doesn't wash with everybody, however. As anthropologist Scott Atran of the University of Michigan in Ann Arbor points out, the benefits of holding such unfounded beliefs are questionable, in terms of evolutionary fitness. "I don't think the idea makes much sense, given the kinds of things you find in religion," he says. A belief in life after death, for example, is hardly compatible with surviving in the here-and-now and propagating your genes. Moreover, if there are adaptive advantages of religion, they do not explain its origin, but simply how it spread.

An alternative being put forward by Atran and others is that religion emerges as a natural by-product of the way the human mind works. That's not to say that the human brain has a "god module" in the same way that it has a language module that evolved specifically for acquiring language. Rather, some of the unique cognitive capacities that have made us so successful as a species also work together to create a tendency for supernatural thinking. "There's now a lot of evidence that some of the foundations for our religious beliefs are hard-wired," says Bloom.

Much of that evidence comes from experiments carried out on children, who are seen as revealing a "default state" of the mind that persists, albeit in modified form, into adulthood. "Children the world over have a strong natural receptivity to believing in gods because of the way their minds work, and this early developing receptivity continues to anchor our intuitive thinking throughout life," says anthropologist Justin Barrett of the University of Oxford.

So how does the brain conjure up gods? One of the key factors, says Bloom, is the fact that our brains have separate cognitive systems for dealing with living things - things with minds, or at least volition - and inanimate objects. This separation happens very early in life. Bloom and colleagues have shown that babies as young as five months make a distinction between inanimate objects and people. Shown a box moving in a stop-start way, babies show surprise. But a person moving in the same way elicits no surprise. To babies, objects ought to obey the laws of physics and move in a predictable way. People, on the other hand, have their own intentions and goals, and move however they choose.

Mind and Matter

Bloom says the two systems are autonomous, leaving us with two viewpoints on the world: one that deals with minds, and one that handles physical aspects of the world. He calls this innate assumption that mind and matter are distinct "common-sense dualism". The body is for physical processes, like eating and moving, while the mind carries our consciousness in a separate - and separable - package. "We very naturally accept you can leave your body in a dream, or in astral projection or some sort of magic," Bloom says. "These are universal views."

There is plenty of evidence that thinking about disembodied minds comes naturally. People readily form relationships with non-existent others: roughly half of all 4-year-olds have had an imaginary friend, and adults often form and maintain relationships with dead relatives, fictional characters and fantasy partners. As Barrett points out, this is an evolutionarily useful skill. Without it we would be unable to maintain large social hierarchies and alliances or anticipate what an unseen enemy might be planning. "Requiring a body around to think about its mind would be a great liability," he says.

Useful as it is, common-sense dualism also appears to prime the brain for supernatural concepts such as life after death. In 2004, Jesse Bering of Queen's University Belfast, UK, put on a puppet show for a group of pre-school children. During the show, an alligator ate a mouse. The researchers then asked the children questions about the physical existence of the mouse, such as: "Can the mouse still be sick? Does it need to eat or drink?" The children said no. But when asked more "spiritual" questions, such as "does the mouse think and know things?", the children answered yes.

Default to God

Based on these and other experiments, Bering considers a belief in some form of life apart from that experienced in the body to be the default setting of the human brain. Education and experience teach us to override it, but it never truly leaves us, he says. From there it is only a short step to conceptualising spirits, dead ancestors and, of course, gods, says Pascal Boyer, a psychologist at Washington University in St Louis, Missouri. Boyer points out that people expect their gods' minds to work very much like human minds, suggesting they spring from the same brain system that enables us to think about absent or non-existent people. The ability to conceive of gods, however, is not sufficient to give rise to religion. The mind has another essential attribute: an overdeveloped sense of cause and effect which primes us to see purpose and design everywhere, even where there is none. "You see bushes rustle, you assume there's somebody or something there," Bloom says.

This over-attribution of cause and effect probably evolved for survival. If there are predators around, it is no good spotting them 9 times out of 10. Running away when you don't have to is a small price to pay for avoiding danger when the threat is real. Again, experiments on young children reveal this default state of the mind. Children as young as three readily attribute design and purpose to inanimate objects. When Deborah Kelemen of the University of Arizona in Tucson asked 7 and 8-year-old children questions about inanimate objects and animals, she found that most believed they were created for a specific purpose. Pointy rocks are there for animals to scratch themselves on. Birds exist "to make nice music", while rivers exist so boats have something to float on. "It was extraordinary to hear children saying that things like mountains and clouds were 'for' a purpose and appearing highly resistant to any counter-suggestion," says Kelemen.

In similar experiments, Olivera Petrovich of the University of Oxford asked pre-school children about the origins of natural things such as plants and animals. She found they were seven times as likely to answer that they were made by god than made by people. These cognitive biases are so strong, says Petrovich, that children tend to spontaneously invent the concept of god without adult intervention: "They rely on their everyday experience of the physical world and construct the concept of god on the basis of this experience." Because of this, when children hear the claims of religion they seem to make perfect sense.

Our predisposition to believe in a supernatural world stays with us as we get older. Kelemen has found that adults are just as inclined to see design and intention where there is none. Put under pressure to explain natural phenomena, adults often fall back on teleological arguments, such as "trees produce oxygen so that animals can breathe" or "the sun is hot because warmth nurtures life". Though she doesn't yet have evidence that this tendency is linked to belief in god, Kelemen does have results showing that most adults tacitly believe they have souls. Boyer is keen to point out that religious adults are not childish or weak-minded. Studies reveal that religious adults have very different mindsets from children, concentrating more on the moral dimensions of their faith and less on its supernatural attributes.

Even so, religion is an inescapable artefact of the wiring in our brain, says Bloom. "All humans possess the brain circuitry and that never goes away." Petrovich adds that even adults who describe themselves as atheists and agnostics are prone to supernatural thinking. Bering has seen this too. When one of his students carried out interviews with atheists, it became clear that they often tacitly attribute purpose to significant or traumatic moments in their lives, as if some agency were intervening to make it happen. "They don't completely exorcise the ghost of god - they just muzzle it," Bering says. The fact that trauma is so often responsible for these slips gives a clue as to why adults find it so difficult to jettison their innate belief in gods, Atran says. The problem is something he calls "the tragedy of cognition". Humans can anticipate future events, remember the past and conceive of how things could go wrong - including their own death, which is hard to deal with. "You've got to figure out a solution, otherwise you're overwhelmed," Atran says. When natural brain processes give us a get-out-of-jail card, we take it.

That view is backed up by an experiment published late last year (Science, vol 322, p 115). Jennifer Whitson of the University of Texas in Austin and Adam Galinsky of Northwestern University in Evanston, Illinois, asked people what patterns they could see in arrangements of dots or stock market information. Before asking, Whitson and Galinsky made half their participants feel a lack of control, either by giving them feedback unrelated to their performance or by having them recall experiences where they had lost control of a situation. The results were striking. The subjects who sensed a loss of control were much more likely to see patterns where there were none. "We were surprised that the phenomenon is as widespread as it is," Whitson says. What's going on, she suggests, is that when we feel a lack of control we fall back on superstitious ways of thinking. That would explain why religions enjoy a revival during hard times.

So if religion is a natural consequence of how our brains work, where does that leave god? All the researchers involved stress that none of this says anything about the existence or otherwise of gods: as Barratt points out, whether or not a belief is true is independent of why people believe it. It does, however, suggests that god isn't going away, and that atheism will always be a hard sell. Religious belief is the "path of least resistance", says Boyer, while disbelief requires effort.

These findings also challenge the idea that religion is an adaptation. "Yes, religion helps create large societies - and once you have large societies you can outcompete groups that don't," Atran says. "But it arises as an artefact of the ability to build fictive worlds. I don't think there's an adaptation for religion any more than there's an adaptation to make airplanes." Supporters of the adaptation hypothesis, however, say that the two ideas are not mutually exclusive. As David Sloan Wilson of Binghamton University in New York state points out, elements of religious belief could have arisen as a by-product of brain evolution, but religion per se was selected for because it promotes group survival. "Most adaptations are built from previous structures," he says. "Boyer's basic thesis and my basic thesis could both be correct."

Robin Dunbar of the University of Oxford - the researcher most strongly identified with the religion-as-adaptation argument - also has no problem with the idea that religion co-opts brain circuits that evolved for something else. Richard Dawkins, too, sees the two camps as compatible. "Why shouldn't both be correct?" he says. "I actually think they are." Ultimately, discovering the true origins of something as complex as religion will be difficult. There is one experiment, however, that could go a long way to proving whether Boyer, Bloom and the rest are onto something profound. Ethical issues mean it won't be done any time soon, but that hasn't stopped people speculating about the outcome.

It goes something like this. Left to their own devices, children create their own "creole" languages using hard-wired linguistic brain circuits. A similar experiment would provide our best test of the innate religious inclinations of humans. Would a group of children raised in isolation spontaneously create their own religious beliefs? "I think the answer is yes," says Bloom.

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God of the gullible

In The God Delusion, Richard Dawkins argues that religion is propagated through indoctrination, especially of children. Evolution predisposes children to swallow whatever their parents and tribal elders tell them, he argues, as trusting obedience is valuable for survival. This also leads to what Dawkins calls "slavish gullibility" in the face of religious claims.

If children have an innate belief in god, however, where does that leave the indoctrination hypothesis? "I am thoroughly happy with believing that children are predisposed to believe in invisible gods - I always was," says Dawkins. "But I also find the indoctrination hypothesis plausible. The two influences could, and I suspect do, reinforce one another." He suggests that evolved gullibility converts a child's general predisposition to believe in god into a specific belief in the god (or gods) their parents worship.

November 19, 2008

Why We Love To Hate Spiders

ResearchBlogging.orgAn article in a recent issue of New Scientist about what is responsible for fear of spiders led me to slightly disagree with the explanations afforded by the researchers. Have a quick read:

"Movies starring the superhero Spiderman may rake in millions at the box office, but the humble spider inspires fear and loathing quite unlike that of other creepy-crawlies. A third of women and a fifth of men admit to being scared of spiders. And an obvious explanation is that we have evolved a dread of spiders because they can be poisonous. However, psychologist Georg Alpers at the University of Würzburg, Germany, and his team believe that if this theory is correct, we would be just as afraid of stinging insects such as bees and wasps.

"To find out if this was the case, Alpers's team asked 76 students to rate photos of spiders, wasps, bees, beetles, butterflies and moths on three counts: how much fear and disgust they inspired and how dangerous the students felt they were. It transpired that spiders triggered far greater fear and disgust than any of the other creatures and were believed to be more dangerous (Evolution and Human Behaviour, DOI: 10.1016/j.evolhumbehav.2008.08.005).

"Stuart Hine, an entomologist at London's Natural History Museum, thinks fear of spiders is probably a learned behaviour. You only have to see someone standing on a chair screaming 'Spider! Spider!' to pick up on that fear, he explains. 'It stems back to the days of plagues when people suspected anything that crawled out of the thatch as carrying disease.'"

Now I think it's fair enough to invoke explanations arising from evolutionary psychology ("poisonous") or about learned behaviour, and I respect that, but couldn't we consider the most obvious explanation: that spiders are just horrible-looking little bastards?

I'd post a picture of a spider to prove my point, but as a recovering arachnophobic I don't think it would be a good idea. After years of screaming and screeching after sighting one of the little blighters, what to speak of being paralysed with fear, I'm pleased to report that I overcame my fear (somewhat) after a school trip to London Zoo. It really is quite amazing what group cohesion in the form of "dares" can do, but suffice it to say that we all forced ourselves to go and look at frightening tarantulas and the like in the Insect House. The first thing I noticed when I saw them is how small they are in reality. Many images available in books and other media tend to be close-ups and enlargements which may account for sudden shock reactions. But seeing them in reality gives one the impression that it is the fear itself which is overblown in the face of their diminutive size. If tarantulas represent an extremity in terms of fear, what more could we say about the even smaller stature of house spiders?

Since that visit to the zoo, my own fear of spiders significantly diminished from hysterical reactions to mild observations. I still exhibit a modicum of fear when I see them, but depending on my mood I may choose to squish them into oblivion or I might catch it and throw it outside.

But why do spiders provoke such extreme reactions? I downloaded and quickly read through the actual paper. Alpers et al. hypothesised that similar reactions should be exhibited with respect to bees and wasps, which could be true except that they seem to pose more of an annoyance than a fear. After all, how many apiphobics or spheksophobics do you know? I'd be more surprised if you've even heard those terms. Reading through the introduction to the study, there is much to be said for the evolutionary perspective in terms of fight-or-flight responses but too much is said about their venomous nature as well as the venomous qualities of other arthropods. Quote: "The disgust hypothesis postulates that emotional responses to spiders are culturally transmitted because these animals were historically associated with disease and infection from medieval times onward. However, it is unclear why mainly spiders, and not other 'creepy crawlies,' have been considered to be responsible for infections and disease."

Hello? Could it be because they look horrible? And could it be because they tend to move very quickly and their eight-legged appearance gives off an unnerving impression? I'm sure that much could be said for visual representation in connection with disgust hypotheses and I'm pretty sure that studies have been carried out along those lines, but you'll have to forgive me for being too lazy to dig them up right now. The researchers go on, this time suggesting that fear of spiders could be down to cultural transmission: "Other arthropods that are comparable in terms of venomousness, appearance, or behavior to spiders may elicit similar reactions, but cultural transmission may exert strong biases on verbal labeling. Individuals who report being afraid of spiders may stick with a cultural stereotype ('fear of spiders is common'), although their fears may be much less specific than commonly thought. A variety of arthropods may elicit fear or disgust (e.g., beetles), but 'fear of spiders' may merely be a culturally accepted verbal label for a wide spectrum of animal fears."

Hello? Did you ever consider that their horrific looks may account for fear??

It's no wonder that the results of the experiments suggested that "spider fear is in fact spider specific". Aside from being venomous, the study gives rise to a more interesting evolutionary question as to why spiders accounted for the highest ratings of fear in both emotional and dangerous contexts as compared to bees/wasps. One explanation provided by the authors relates to the honey-creating capacity of bees that formed part of Early Man's diet. Frequent interactions with bees due to honey obtainment and the very real possibility of being stung regularly may have contributed to an adaptive response on the human part with the result of lessening fear. In other words, surviving bee stings would be worth the trouble of obtaining the honey necessary to eat (reward). In spite of the relative rarity of spider stings, interaction with them offers no evolutionary advantage and this leads to a general lack of information about them. Which in turns contributes to informational fear acquisition that is culturally transmitted through generations, often taking the form of myths.

Another explanation relates to their unpredictable and uncontrollable behavior that could be gleaned from their rapid or abrupt movements (aha, now we're finally getting there!). Earlier studies suggest that this could be down to the inability of humans to exert control or influence upon the movements of animals, but many other animals and insects move as fast (or faster than) spiders and this is insufficient to explain spider-specific fear. After some more discussion of other points, the authors recognise one of the limitations of their study in showing static pictures to the participants as opposed to animated, or even 'live' images, and thus responses to spider/insect mobility couldn't be obtained and tested. Whereas spiders tend to be detected extremely quickly in search tasks (and where some say this is observable for other animals), the elevated fear and digust ratings in this study allow the researchers to recognise the 'specality' of spider fear. Very generously, they also recognise that existing explanations for these responses (venomousness and so on) aren't sufficient or well-founded to properly explain them.

They could start by studying reactions to sudden spider appearances, and to what extent this is moderated by their looks!

Thankfully (and at long last!) the researchers do end up suggesting two specific ways to deeply analyse the origin of animal (spider?) fear and disgust; first through detailed cross-cultural studies, and secondly by analysing the morphological and behavioural traits that trigger the fear and disgust responses.

Hallelujah! It was a long ride but they got there in the end! And I think when that kind of study is carried out and published, it will be a worthwhile read.
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A GERDES, G UHL, G ALPERS (2008). Spiders are special: fear and disgust evoked by pictures of arthropods☆ Evolution and Human Behavior DOI: 10.1016/j.evolhumbehav.2008.08.005