Predictably irrational, variably dishonest

Behavioural economist Dan Ariely was the guest on the latest edition of ABC Radio National’s All in the Mind where he discusses why we’re so bad at predicting what’s best for us, and why honesty is a shifty behaviour.

As well as being a researcher, Ariely is also author of a psychology book called Predictably Irrational which is currently riding high in the book charts.

It’s worth catching the mp3 version of the programme, as it’s slightly extended, and I found the last part, where Ariely talks about honesty, the most interesting.

Using various experimental conditions where participants are given varying degrees of room for dishonesty, Ariely notes that people tend to be dishonest enough to give themselves an advantage, but suggests we’re not so dishonest to feel bad about ourselves.

In other words, he’s suggesting that honesty is a cognitive dissonance style reasoning process, balancing our desire for personal gain against our willingness to believe in ourselves as a ‘good person’ – an idea explored further in a forthcoming paper [pdf] by Nina Mazar and Dan Ariely.

If you’re interested in a good overview of the psychology of honesty and deception, I’ve just read a fantastic paper [pdf] by the same pair, which is fascinating as much for its insights into what influences our level of honesty for its recommendations about applying the research to encourage people to be more honest.

It notes that getting people to focus on themselves increases honesty, as does getting them to focus on moral ideas, such as the Ten Commandments.

In their experiment, participants were told to write down either as many of the Ten Commandments as they could remember (increased self-awareness of honesty) or the names of ten books that they read in high school (control). They had two minutes for this task before they moved on to an ostensibly separate task: the math test. The task in the math test was to search for number combinations that added up to exactly ten. There were 20 questions, and the duration of the experiment was restricted to five minutes. After the time was up, students were asked to recycle the test form they worked on and indicate on a separate collection slip how many questions they solved correctly. For each correctly solved question, they were paid $.50.

The results showed that students who were made to think about the Ten Commandments claimed to have solved fewer questions than those in the control. Moreover, the reduction of dishonesty in this condition was such that the declared performance was indistinguishable from another group whose responses were checked by an external examiner. This suggests that the higher self-awareness in this case was powerful enough to diminish dishonesty completely.

However, I wonder whether the effect of focusing on the Ten Commandments was due to their moral or supernatural associations.

I am reminded of Eric Schwitzgebel’s ongoing project on why ethics professors, who think about moral issues a lot, are no more moral (and perhaps less!) than other people, and a study [pdf] by psychologist Jesse Bering that found that simply telling participants that the lab was haunted increased honesty in a computer task.

Link to Dan Ariely on All in the Mind.
pdf of Mazar and Ariely’s paper on the psychology of dishonesty.

Twisted thoughts

This wonderful knitted brain is by artist Sarah Illenberger. Presumably, we’re looking down on the brain with the two hemispheres slightly separated.

She has also created other wonderful anatomically correct organs, including the heart and the intestines.

It seems this one might be a possible inductee into the Museum of Scientifically Accurate Fabric Brain Art.

Link to Sarah Illenberger’s wonderful creations.
Link to Museum of Scientifically Accurate Fabric Brain Art.

Rock climbing hacks! (now with added speculation)

reach.jpgI’m going to tell you about an experience that I often have rock-climbing and then I’m going to offer you some speculation as to the cognitive neuroscience behind it. If you rock-climb I’m sure you’ll find my description familiar. If you’re also into cognitive neuroscience perhaps you can tell me if you think my speculation in plausible.

Rock-climbing is a sort of three-dimensional kinaesthetic puzzle. You’re on the side of rock-wall, and you have to go up (or down) by looking around you for somewhere to move your hands or feet. If you can’t see anything then you’re stuck and just have to count the seconds before you run out of strength and fall off. What often happens to me when climbing is that I look as hard as I can for a hold to move my hand up to and I see nothing. Nothing I can easily reach, nothing I can nearly reach and not even anything I might reach if I was just a bit taller or if I jumped. I feel utterly stuck and begin to contemplate the immanent defeat of falling off.

But then I remember to look for new footholds.

Sometimes I’ve already had a go at this and haven’t seen anything promising, but in desperation I move one foot to a new hold, perhaps one that is only an inch or so further up the wall. And this is when something magical happens. Although I am now only able to reach an inch further, I can suddenly see a new hold for my hand, something I’m able to grip firmly and use to pull myself to freedom and triumph (or at least somewhere higher up to get stuck). Even though I looked with all my desperation at the wall above me, this hold remained completely invisible until I moved my foot an inch — what a difference that inch made.

Psychologists have something they call affordances (Gibson, 1977, 1986), which are features of the environment which seem to ‘present themselves’ as available for certain actions. Chairs afford being sat on, hammers afford hitting things with. The term captures an observation that there is something very obviously action-orientated about perception. We don’t just see the world, we see the world full of possibilities. And this means that the affordances in the environment aren’t just there, they are there because we have some potential to act (Stoffregen, 2003). If you are frail and afraid of falling then a handrail will look very different from if you are a skateboarder, or a freerunner. Psychology typically divides the jobs the mind does up into parcels : ‘perception’, (then) ‘decision making’, (then) ‘action’. But if you take the idea of affordances seriously it gives lie to this neat division. Affordances exist because action (the ‘last’ stage) affects perception (the ‘first’ stage). Can we experimentally test this intuition, is there really an effect of action on perception? One good example is Oudejans et al (1996) who asked baseball fielders to judge were a ball would land, either just watching it fall or while running to catch it. A model of the mind that didn’t involve affordances might think that it would be easier to judge where a ball would land if you were standing still; after all, it’s usually easier to do just one thing rather than two. This, however, would be wrong. The fielders were more accurate in their judgements — perceptual predictions basically — when running to catch the ball, in effect when they could use base their judgements on the affordances of the environment produced by their actions, rather than when passively observing the ball.

The connection with my rock-climbing experience is obvious: although I can see the wall ahead, I can only see the holds ahead which are actually within reach. Until I move my foot and bring a hold within range it is effectively invisible to my affordance-biased perception (there’s probably some attentional-narrowing occurring due to anxiety about falling off too, (Pijpers et al, 2006); so perhaps if I had a ladder and a gin and tonic I might be better at spotting potential holds which were out of reach).

There’s another element which I think is relevant to this story. Recently neuroscientists have discovered that the brain deals differently with perceptions occurring near body parts. They call the area around limbs ‘peripersonal space’ (for a review see Rizzolatti & Matelli, 2003). {footnote}. Surprisingly, this space is malleable, according to what we can affect — when we hold tools the area of peripersonal space expands from our hands to encompass the tools too (Maravita et al, 2003). Lots of research has addressed how sensory inputs from different modalities are integrated to construct our brain’s sense of peripersonal space. One delightful result showed that paying visual attention to an area of skin enhanced touch-perception there. The interaction between vision and touch was so strong that providing subjects with a magnifying glass improved their touch perception even more! (Kennett et al, 2001; discussed in Mind Hacks, hack #58). I couldn’t find any direct evidence that unimodal perceptual accuracy is enhanced in peripersonal space compared to just outside it (if you know of any, please let me know), but how’s this for a reasonable speculation — the same mechanisms which create peripersonal space are those which underlie the perception of affordances in our environment. If peripersonal space is defined as an area of cross-modal integration, and is also malleable according to action-possibilities, it isn’t unreasonable to assume that an action-orientated enhancement of perception will occur within this space.

What does this mean for the rock-climber? Well it explains my experience, whereby holds are ‘invisible’ until they are in reach. This suggests some advice to follow next time you are stuck halfway up a climb: You can’t just look with your eyes, you need to ‘look’ with your whole body; only by putting yourself in different positions will the different possibilities for action become clear.

(references and footnote below the fold)

Continue reading “Rock climbing hacks! (now with added speculation)”

English Surgeon reminder

Just a reminder for our readers that have access to the BBC TV channel, BBC Two, that the stunning documentary on neurosurgeons Henry Marsh and Igor Kurilets that we featured previously on Mind Hacks will be shown on Sunday 30th March at 10.55pm

British residents will be able to watch it over the net for a week after on BBC’s iPlayer, which I’ll link to as soon as it appears online.

Everyone else is going to have to wait for a torrent, but I’ll keep an eye out and post a link if one appears.

Either way, Henry Marsh was the first guest on BBC Radio 4’s Midweek which you can listen to via the programme’s webpage.

Link to BBC 2 listing for documentary.
Link to Midweek discussion with Marsh.

Lancet and MNI neuroscience podcasts

I’ve just discovered a couple of great high class neuroscience podcasts. The first is the Lancet Neurology podcast and the second is series of podcasts and video from the Montreal Neurological Institute.

The Lancet Neurology podcasts are all-too-brief but are really well done. In contrast to the American Academy of Neurology podcasts we featured previously, they’re quite accessible even to the non-neurologist.

The MNI is one of the most famous hospitals and neuroscience research centres in the world, and needless to say they have some wonderfully produced podcasts and some great video lectures online. A treasure trove of useful brain listening.

Link to Lancet Neurology podcast.
Link to Montreal Neurological Institute podcasts and video.

Impact of digital media review hits the wires

Psychologist Dr Tanya Byron has just released a remarkably sensible review on the effect of digital media on children, commissioned by the UK government.

Tanya Byron is great. She came to prominence as the resident psychologist on several UK TV parenting programmes but used evidence-based interventions, essentially demonstrating what a clinical psychologist would do if your child got referred for behaviour problems.

Most notably, she obviously knew her shit and is widely respected among clinical psychologists. Despite often being described as a ‘TV psychologist’ she remained working in the NHS at the coal face of clinical work.

She’s just published her review on the effects of the internet and computer games on children and has been remarkably level-headed in a time when the media loves ‘internet addiction’ and ‘computer games make killer kids’ stories.

BBC News has a video interview with her (skip to 1m20s to avoid the preamble). As well as refusing to soundbite the complexity of the issues, she’s not afraid to use uses phrases like “causal models of harm” and “research effects literature” in interviews. Go Tanya!

The full report [pdf] is long, and I’ve not read it all, but I really recommend reading the summary on pages 3-5. Here’s some key points:

4. …Overall I have found that a search for direct cause and effect in this area is often too simplistic, not least because it would in many cases be unethical to do the necessary research. However, mixed research evidence on the actual harm from video games and use of the internet does not mean that the risks do not exist. To help us measure and manage those risks we need to focus on what the child brings to the technology and use our understanding of children‚Äôs development to inform an approach that is based on the ‚Äòprobability of risk‚Äô in different circumstances.

5. We need to take into account children‚Äôs individual strengths and vulnerabilities, because the factors that can discriminate a ‚Äòbeneficial‚Äô from a ‚Äòharmful‚Äô experience online and in video games will often be individual factors in the child. The very same content can be useful to a child at a certain point in their life and development and may be equally damaging to another child. That means focusing on the child, what we know about how children‚Äôs brains develop, how they learn and how they change as they grow up. This is not straightforward ‚Äì while we can try to categorise children by age and gender there are vast individual differences that will impact on a child‚Äôs experience when gaming or online, especially the wider context in which they have developed and in which they experience the technology…

Her recommendations focus on the all too pressing point that kids often vastly outclass adults in understanding the technology and that parents are often not competent in being able to guide children as they’d wish.

Needless to say, Byron recommends that parents need support and guidance themselves in being able to regulate their children’s use of new technology.

From what I’ve read so far, it’s clear that Byron has understood both the psychological research and the technology. No mean feat in an age where commentators often demonstrate little except the fact that they are a bit baffled by this new fangled interweb thing.

Link to Byron review webpage.
Link to BBC News on the report and interview.

2008-03-28 Spike activity

Quick links from the past week in mind and brain news:

PsychCentral tackles the recent internet addiction nonsense and asks What’s That Smell? It turns out it’s Internet Addiction Disorder in The News.

BBC Radio 4’s excellent history of ideas programme In Our Time has recently had editions on the philosopher Kierkegaard and early computationalist Ada Lovelace.

The BPS Research Digest explains a new study on frustrating tip-of-the-tongue states with bonus bit on how to overcome them.

Psychedelic artist extraordinaire, Alex Grey, is interviewed in the San Francisco Chronicle about his art and tripping (thanks Laurie!)

Dr Petra Boyton looks at international headlines linking anger, mental illness and Britain and notes that they’re based on a rather dodgy market research survey.

The limits of certainty in diagnosis and medicine are explored by The New York Times.

Neurophilosophy looks at a comparative study on the possible evolutionary development of a key language pathway in the brain.

Removing brain tumours can be tricky at the best of times, especially when the operation is on a 7-year-old-girl. The New York Times has an article and video on one such procedure.

Scientific American Mind looks at the effects of the surprisingly common occurrence of postpartum (post-pregnancy) depression beyond the individual effect on the mother.

In praise of booze. The New Humanist shings the praises of the world’s favourite fight enabler.

The New York Times has a review of the Willard hospital suitcase exhibition we featured the other day.

The application of shoe smell to epileptic seizures. No really. Neurocritic has some fantastic coverage of an upcoming scientific article on the phenomenon.

New Scientist reports that belly fat linked to increased risk for dementia. Not particularly startling, but emphasises the point that one of the best ways of keeping your brain healthy is to look after your cholesterol, blood pressure and cardiovascular fitness.

The six degrees of autism. Discover Magazine has a funky network analysis of schizophrenia, bipolar and autism comorbidity.

Wired reports that Pfizer computers have been hacked to send out, wait for it, v1agra spam.

A thorough debunking of determining personality from handwriting can be found on PsyBlog.

The New York Review of Books has a megareview of several books on happiness.

Sharp Brains has a fantastic article by neuroscientist Shannon Moffett on sleep, Tetris, memory and the brain.

Ray Kurzweil hacks body, mind, eternity

Wired has as article on the immortality-seeking inventor and transhumanist Ray ‘King Canute’ Kurzweil who is attempting to defeat death by bioengineering his body until he can upload his mind on a computer.

Transhumanism is a movement that attempts to extend the limits of human existence through technology, and one of the obvious, if not slightly fanciful, hurdles is to transcend death.

One of the key concepts in transhumanism is the singularity, supposedly the point where computers will ‘overtake’ the human brain in terms of their processing ability and, hence, intelligence as we know it will become completely transformed.

Accompanying the article about Kurzweil’s wide-eyed optimism is another article on the current science of his objectives which nicely illustrates where the conceptual gaps actually lie.

Many computer scientists take it on faith that one day machines will become conscious. Led by futurist Ray Kurzweil, proponents of the so-called strong-AI school believe that a sufficient number of digitally simulated neurons, running at a high enough speed, can awaken into awareness. Once computing speed reaches 1016 operations per second — roughly by 2020 — the trick will be simply to come up with an algorithm for the mind.

Which is a bit like saying “once we have the technology to travel to another galaxy, all we have to do is get there”.

Link to Wired article on Kurzweil.
Link to Wired article on the science of transhumanism.

Brain lamp

Designer Alexander Lervik created this wonderful table lamp based on a 3D reconstruction of his own brain scan.

MYBrain. The table lamp

A replica of the designer’s brain, originated from an MR scan at the Karolinska Institute in Stockholm.

The image was processed through a 3D-printer, and became this unusual lamp shade design. Yes, it is bright.”

Although perhaps the coolest, this is not the first brain lamp we’ve come across.

Indeed, it would make a good accompaniment to the plasma brain lamp we featured back in early 2007.

Link to designer’s page for the brain lamp (via BoingBoing).

Lost in translation

ABC Radio National’s The Philosopher’s Zone recently broadcast a programme that tackled the philosophy of translating between languages – discussing whether particular ideas are just harder to express in certain languages, and whether it is possible ever to tie a word to a definite meaning.

As I’ve mentioned before, I’m fascinated by words which don’t translate across languages, especially when they related to mental states or psychology.

One of my favourites is the Portuguese word saudade, which, as far as I can work out, refers to a type of wistful or sombre yearning for something that you’ve experienced in the past, with the underlying feeling that the wished for thing might never return and that the feeling is all that you have.

The programme looks at these issues beyond the case of single words, asking whether some sorts of thinking are a product of the language, which possibly allows for concepts to be dealt with in a different manner.

One of the most striking differences lies between analytic philosophy, largely produced by native English speakers that entails legal or scientific style reasoning as applied to concepts, and continental philosophy, which often deals with criticising the concepts of language itself and relies much more on rhetoric and analogy.

The most famous continental philosopher are French (Derrida, Foucault, Deleuze etc), so this provides a useful starting point for discussing whether the different approaches to philosophy are just the result of culture, or stem from the tools of language itself.

The second part of the programme deals with W.V. Quine’s views on language, which suggest that there is no definite distinction between statements we assume are meaningful by definition (e.g. a bachelor is an unmarried man) and those which are only true with reference to the outside world (e.g. the sun is shining in London).

Interestingly, the programme avoids discussing Wittgenstein, who thought that all philosophical issues were really just difficulties brought about by language.

Anyway, a fascinating discussion of an important topic.

Link to The Philosopher’s Zone on the philosophy of language.

Demanding sex differences

Language Log has a great post looking at differences in empathy between males and females, and highlights a new study showing race differences as well.

The punchline is that it’s actually really hard to say whether either of these results reflect true differences because the samples tend to be unrepresentative of the population, and measures of empathy tend to be influenced by the social situation in which they’re taken.

They grab this paragraph from a review article on empathy measurement:

In general, sex differences in empathy were a function of the methods used to assess empathy. There was a large sex difference favoring women when the measure of empathy was self-report scales; moderate differences (favoring females) were found for reflexive crying and self-report measures in laboratory situations; and no sex differences were evident when the measure of empathy was either physiological or unobtrusive observations of nonverbal reactions to another’s emotional state.

This article is from way back in ’83, but more recent studies have tended to support the main idea that the overall difference between men and women in empathy is fairly negligible when behaviour, rather than self-report, is examined.

These sorts of social influences on experimental findings are known as ‘demand characteristics‘.

The classic example is an attractive female researcher asking men about penis size, but the effects can be quite subtle and only come to light in subsequent replications of the study (if at all!).

One of my favourite studies in this area looked at the supposed tendency for people who experience ‘sensory deprivation’ to have hallucinations and suffer severe emotional and cognitive impairment.

In 1964 psychologists Martin Orne and Karl Scheibe compared two groups of participants in a sensory deprivation experiment.

One group of participants was greeted by white coated researchers standing next to emergency equipment, were asked for their medical history and given serious looking tests, were told to report any strange sensory distortions and were informed that if they wanted to stop the experiment, they had to press a panic button.

The other group was greeted informally by researchers in casual clothes, weren’t given any medical checks, and were told to report their experiences freely as they occurred. To stop the experiment, they just had to knock on the window.

The actual sensory deprivation procedure was the same for both groups, but the participants given the formal medical introduction reported greater emotional disturbance, unusual experiences and mental distress. Furthermore, they tended to do much worse on the cognitive tests given afterwards.

While this didn’t ‘disprove’ any of the unpleasant effects of sensory deprivation, it did show that they are heavily mediated by expectation which is implicitly inferred from the testing situation.

Needless to say, this can affect any type of study, so scientists are always on the look out to see if it might be responsible for new findings.

Link to Language Log article on empathy, sex and race.
Link to study on demand characteristics and sensory deprivation.

Court imitates life in antipsychotic drug battle

The New York Times has an article which skilfully captures one of the central dilemmas in mental health: deciding whether the benefits of psychiatric drugs outweigh their side-effects for any individual patient.

The story centres on the ongoing court case where the state of Alaska are suing drug company Eli Lilly over claims that the multinational failed to inform professionals and the public about the side-effects of the antipsychotic drug olanzapine (Zyprexa) despite knowing about them for some time.

Olanzapine is a useful and effective drug for managing psychosis and, for some people, the only effective treatment for severe mental illness.

But, like the other newer generation drugs in this class, causes weight gain and significantly increases the risk for heart disease and diabetes. Like all other antipsychotics, it can also leave you feeling groggy and reduce your ability to experience pleasure (owing to the fact it affects the dopamine ‘reward’ system).

While mental health professionals tend to focus on the benefits of the drug for the person’s mental state, patients tend to focus on its negative effects on their health and enjoyment.

This differing focus is partly because the mental health professionals, on the whole, are not the ones who have to take the drugs and experience their side-effects, but also because psychosis often means the person does not realise their thinking has become disturbed, meaning they don’t see the point of being prescribed medication in the first place.

This dilemma was rather poignantly mirrored in the Alaska court house. While the Alaska vs Eli Lilly case was going on in one courtroom, in the next was a case concerning whether an obviously disturbed man should be compelled to take olanzapine by his hospital.

The NYT piece covers the two cases, drawing parallels between the individual dilemma and the landmark legal action, and captures the dilemma very succinctly.

Link to NYT article ‘One Drug, Two Faces’ (via Furious Seasons).
Link to Furious Seasons coverage of the Alaska vs Eli Lilly case.

Why do some people sleepwalk?

I just found this short-but-sweet explanation for why sleepwalking occurs by neurologist Antonio Oliviero. It appears in this month’s Scientific American Mind:

People can perform a variety of activities while asleep, from simply sitting up in bed to more complex behavior such as housecleaning or driving a car. Individuals in this trancelike state are difficult to rouse, and if awoken they are often confused and unaware of the events that have taken place. Sleepwalking most often occurs during childhood, perhaps because children spend more time in the “deep sleep” phase of slumber. Physical activity only happens during the non–rapid eye movement (NREM) cycle of deep sleep, which precedes the dreaming state of REM sleep.

Recently my team proposed a possible physiological mechanism underlying sleepwalking. During normal sleep the chemical messenger gamma-aminobutyric acid (GABA) acts as an inhibitor that stifles the activity of the brain’s motor system. In children the neurons that release this neurotransmitter are still developing and have not yet fully established a network of connections to keep motor activity under control. As a result, many kids have insufficient amounts of GABA, leaving their motor neurons capable of commanding the body to move even during sleep. In some, this inhibitory system may remain underdeveloped—or be rendered less effective by environmental factors—and sleepwalking can persist into adulthood.

As a bonus, the page also has an explanation of why we experience the painful ‘brain freeze’ sensation when we eat ice cream too quickly.

UPDATE: Thanks to Danielle for sending this fascinating snippet:

I used to have a VERY SEVERE sleepwalking problem. This past summer, I researched the use of GABA for mild anxiety. Although there was a great deal of question over whether it could cross the blood-brain barrier, I thought it was worth a try. It didn’t work for anxiety at all – but I was surprised to notice that it cured my sleepwalking, which was completely unexpected! Now that I know more about the connection between GABA, slow-wave sleep, & sleepwalking, it makes sense. I think there may be real treatment or research potential there, but I have no idea to whom I should report this. Maybe you can do something with it?

Link to SciAmMind sleepwalking and brain freeze explanations.

The Lives They Left Behind

PsychCentral has alerted me to a wonderful online exhibit based on the lives of several psychiatric patients whose belongings were found in suitcases in an old asylum attic years after they had passed away.

All the individuals were patients at the Willard Asylum, some for as long as 62 years.

Unfortunately, the site is a bit over-Flashed which means it’s not the most intuitive to navigate, but it’s worth grappling with the menus at the bottom of the screen as the stories are incredibly touching.

The photo on the right is of ‘Frank’:

On June 7, 1945, Mr. Frank #27967 went into the Virginia Restaurant on Fulton Street in Brooklyn and was served a meal on a broken plate. He became upset and caused a disruption outside the restaurant, yelling and kicking garbage cans. The police were called, and, instead of arresting him, brought him to the psychiatric ward at Kings County Hospital. From there, he was transferred to Brooklyn State Hospital, and on April 9, 1946, he was admitted to Willard, one of a growing number of African American patients transferred to Willard from New York City in the 40s, due to over-crowding…

Mr. Frank # 27967 never escaped the consequences of that day outside the restaurant in 1945. In 1949, he was transferred from Willard to the Veterans Administration hospital in Canandaigua, NY, and in 1954 to the VA hospital in Pittsburgh. He died there 30 years later, having spent more than half his life in an institution.

The site also has a great deal of information about the hospital itself, audio recordings of memories of the institution and more information about the book and touring exhibition which is on the road right now.

In fact, it’s currently on show at the Cayuga Museum of History and Art in Auburn, New York.

Link to The Lives They Left Behind online exhibit.

Where angels no longer fear to tread

The Economist has an article which serves as an interesting summary of some of the recent work on the psychology and neuroscience of religious belief.

It’s a little bit clumsy in places. For example, it summarises some of the work on the role of the temporal lobes as saying that “religious visions are the result of epileptic seizures that affect this part of the brain”.

Certainly, temporal lobe seizures are associated with religious experiences. A recent review reported that about 0.5% to 3% of people with the condition experience them.

But this work suggests that this is only one factor and actually minor functional changes are probably more important in the general population [pdf].

It’s also important to note that this sort of neuroscience research typically looks at beliefs and experiences concerning the ‘supernatural’ elements of religion.

However, the Economist article also discusses some recent psychological research looking at the influence of religion on social reasoning and touches on the possible evolutionary explanations for the widespread and persistent nature of religious ideas.

Link to Economist article ‘Where angels no longer fear to tread’.