Did genes shape my mother tongue? June 6, 2013

Intuitively, one is inclined to answer with a resounding ‘no’. Of course not, had I been adopted by Thai parents, I would speak Thai. But I was not. My parents and my mother tongue are German. Still, there is a growing opinion that genes do nonetheless play a role.

Before looking at this opinion, it is worth asking why genes shouldn’t play a role in language. A computational model by Andrea Baronchelli of Northeastern University presents a good case. It suggests that the great diversity of languages is due to fast language change. This in turn favours generalist language learners who are able to learn any language equally well. Why? Well, genes are slow to change. Language presents a moving target for evolutionary mechanisms. Instead of adapting to any language in particular, people who can learn any language are at an advantage.

Her genes are different to mine, as is her language. Coincidence?

It is thus crucial to look at the rate of language change: is it slow enough for genes to change in response to it? An examination of the connections between modern languages which emerged out of a common origin and separated millennia ago gives some clues as to the real rate of language change. For example, the first European visitors to India noticed curious commonalities between Indian languages such as Sanskrit (3 = ‘tráyas’) and European ones such as ancient Greek (‘treĩs’) and Latin (‘trēs’). Since the time of the split between European and Indian languages these words do not appear to have changed much.

Nowadays, this can be extended beyond mere anecdotes. In a 2007 article in Nature, Mark Pagel and colleagues showed that the more often a word is used today the more likely it is to be similar across languages with a common origin, even if this connection lies 7,500 years in the past. Using structural features, such as grammar systems and the inventory of language sounds, one can look even up to 12,000 years into the past. These numbers correspond to approximately a quarter of the time the world’s languages had in order to differentiate! So, yes, language vocabulary and structural features do indeed change quickly, but still, there are exceptions, for example among the very common words. This opens up the possibility that genes – which are quite stable – do influence at least those language features which have been found to be consistent for thousands of years.

What is missing so far is an actual example of such a gene-language link. It was found by Dan Dediu and Robert Ladd who looked at tone, a feature which is a relatively stable language characteristic. Tone refers to the use of pitch differences to differentiate words. Take this Thai tongue twister, for example: /mǎi mài mâi mái/. The same consonants and vowels get repeated with different pitches resulting in the sentence ‘Does new silk burn?’. Dediu and Ladd noticed a surprising parallel between the location of tone languages and the location of different versions of two genes in the world, as can be seen on the following map. They tested this gene-tone relation formally and it emerged that it is unusually strong among the possible combinations of genes and structural language features. Furthermore, it does not appear to be due to historical accidents or geographic patterns alone. These two genes called ASPM and Microcephalin are somehow linked to whether a language uses tone. How can that be?

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Geographic distribution of A) one version of ASPM, B) one version of Microcephalin, C) and tone languages.

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The most straight forward explanation would be that there is a tone gene – if you have it in one version you can learn tone otherwise not. Dediu and Ladd reject such a direct account – my own ASPM and Microcephalin versions do not determine whether I will ever be able to learn Thai. Instead, genes could exert a subtle effect, nudging successive generations of language learners in a certain direction. Imagine a bunch of German children were dropped on a lonely island and they learnt Thai from Thai native teachers. They would probably manage very well and their teachers would be very proud. Without their teachers noticing it, however, the German children struggled a bit with the Thai tone system. Over generations, this struggle would reduce tonality bit by bit. Were Thai teachers to discover this island again a few hundred years later, they would be astonished what an odd version of Thai people spoke on the island. A Thai without tone.

So, because language is a not a homogenous ever-changing system, but instead a mix of stable and less stable features, the former could potentially be influenced by genes which are known to be stable as well. So, did genes shape my mother tongue? In a sense yes, the combined genetic background of generations of German speakers shaped German. In another sense no, my genes did not determine that German would end up being my mother tongue. Both answers are true.

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Auroux, S. (2000). History of the Language Sciences. Berlin, New York: Walter de Gruyter.

Baronchelli A, Chater N, Pastor-Satorras R, & Christiansen MH (2012). The biological origin of linguistic diversity. PloS one, 7 (10) PMID: 23118922 doi:10.1371/journal.pone.0048029

Dediu D, & Cysouw M (2013). Some structural aspects of language are more stable than others: a comparison of seven methods. PloS one, 8 (1) PMID: 23383035 doi:10.1371/journal.pone.0055009

Dediu D, & Levinson SC (2012). Abstract profiles of structural stability point to universal tendencies, family-specific factors, and ancient connections between languages. PloS one, 7 (9) PMID: 23028843doi:10.1371/journal.pone.0045198

Pagel M, Atkinson QD, & Meade A (2007). Frequency of word-use predicts rates of lexical evolution throughout Indo-European history. Nature, 449 (7163), 717-20 PMID: 17928860 doi:10.1038/nature06176

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Notes:.

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‘approximately a quarter of the time the world’s languages had in order to differentiate’

Assuming a) a common origin lying 10,000 years in the past and b) one language which existed 40,000 years ago when some of its speakers left Africa to populate the world. The latter estimate is taken from: Diamond, J.: Guns, Germs, and Steel

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‘tone, a feature which is a relatively stable language characteristic’

Across language families, it is ranked the 15th most stable structural language feature among 68 investigated by Dediu and Levinson (2012). Across different ways of quantifying stability, it is ranked 19th out of 62 (Dediu & Cysouw, 2013).

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‘Take this Thai tongue twister, for example: /mǎi mài mâi mái/.’

You can listen to it here (go to 4. The most difficult word and tongue twisters)

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Figures:

1) By YashiWong (Own work), via Wikimedia Commons

2) p. 288 in: Dediu D (2011). Are languages really independent from genes? If not, what would a genetic bias affecting language diversity look like? Human biology, 83 (2), 279-96 PMID: 21615290
http://dx.doi.org/10.3378/027.083.0208

Feeling someone else’s sensation of touch – the neural background, the examples, and you May 28, 2013

Touch is the only sensation which we cannot share with another person. The immediacy of touch differentiates it from the distant impressions which sight and audition can give us. However, modern neuroscience is currently revising this picture: you can touch at a distance. One just doesn’t notice it. Can we find people who do?

A very possessive romantic partner may mind when his love interest was looked at. But it is a whole different game if touch was involved. There is something intuitively different about touch which pervades every day culture. It is, arguably, the lack of distance, the necessary intrusion of the touching object into personal space. This makes touching a very personal experience, far more so than seeing or hearing.

Modern neuroscience is currently revising this picture. The first report to challenge the immediacy of touch came out in 2004. A team led by Christian Keysers found that when people saw someone else being touched on the leg they showed activation in the same brain area as when their legs were being touched directly. Curiously, seeing touch from a first person perspective led to similar brain region activity as seeing it from a third person.

What it looks like to see touch and being touched in the secondary somatosensory cortex.

This got several laboratories around the world started on the topic. For example, recently, Schaefer and colleagues showed that when hands are touched or seen to be touched, perspective does actually matter – a first person view-point increases activation more in primary areas than a third person perspective. In any event, the general picture was not a statistical fluke but instead a replicable finding – being touched is represented in a very similar way in the brain as seeing someone else being touched. But this raises two questions: why can’t I feel anything then and why does it happen?

In 2009, Ramachandran and Brang published a paper which may provide an answer to the first question. They studied four amputees who had lost one hand due to accident. When they watched an experimenter being touched on her hand, the lost hand’s phantom ‘felt the touch’ after a few seconds. One anecdote shows the power of this finding:

‘Patient 1 even added that after we had demonstrated this, he had gone home and asked his wife to massage her own hand while he watched, and watching her do so seemed to relieve his phantom pain.’

Importantly, this was not the case for intact hands – whether of control participants or the amputees. The difference, thus, appears to be whether the sensation felt by others is in competition with the own direct input from the skin. If so, the own touch wins the competition and one does not consciously feel someone else’s experience. But without a hand providing direct sensory input – as in the case of amputees – the touch felt by others becomes vivid.

Apes (of the non-human variety) collaborating.

This still leaves the question as to why this happens. The common explanation is that having the capacity to feel the touch of someone else – even if it is so faint as to be below the level of awareness – aids our ability to understand others. As a social species we need a high level of empathy in order to work together efficiently. Evolutionary ancestors who had a touch-empathy link may have been better at collaborating and, thus, were better able to survive and reproduce.

The current account makes an interesting prediction. Next time you have an anaesthetized hand or foot – and thus no own skin-sensation – you might want to check whether you can feel someone else’s touch. Let me know whether it worked. This experiment has not, as far as I can tell, be done, yet. You yourself could disprove the immediacy of touch.

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Keysers C, Wicker B, Gazzola V, Anton JL, Fogassi L, & Gallese V (2004). A touching sight: SII/PV activation during the observation and experience of touch. Neuron, 42 (2), 335-46 PMID: 15091347

Ramachandran VS, & Brang D (2009). Sensations evoked in patients with amputation from watching an individual whose corresponding intact limb is being touched. Archives of neurology, 66 (10), 1281-4 PMID: 19822785

Schaefer M, Heinze HJ, & Rotte M (2012). Close to you: embodied simulation for peripersonal space in primary somatosensory cortex. PloS one, 7 (8) PMID: 22912698

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Figures:

1) adapted from Keysers et al., 2004, p. 337

2) By Ikiwaner (Own work)  via Wikimedia Commons

The ironic effect of German PhD prestige May 7, 2013

What would happen if a culture actually believed that a PhD does confer such a great set of transferable skills and is such an important test of character that the title is a career boost? A look at Germany gives an impression but it is not the science policy heaven one might expect.

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By now she is just Schavan, ex-science minister.

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There can be no doubt that a PhD is associated with career boost in Germany. Just look at numbers like these: in 2005 in the US 6% of CEOs had a PhD, in France it was 4%. In Germany, however, the number was a full 59%. Note that this is not because more than half of the university graduates who leave German universities do so with a PhD in hand. Only 11% do. Actual pay mirrors this pattern. With merely a university diploma a female graduate gets nearly a third less pay than her PhD colleague.The message to ambitious people is clear: get that PhD no matter what career you want to pursue.

Moreover, having a German PhD is more than just a boost to one’s career. It is a boost to one’s entire social standing. Once the title is obtained it will cover one’s doorbell, one’s business card and even one’s passport. One will expect to be addressed with this title. In many respects it has become the modern equivalent of a title of nobility.

At first, this may sound like science policy heaven. There is a country where people who have earned scientific qualifications have got such a high social standing that they easily reach the highest ladders of society. The claims of transferable skills, test of character, training in critical thinking and analysis, … There is seemingly no need to convince Germans of these things, no need to do advertisements for science education, it appears. However, the opposite could be true. People who want to reach the highest ladders of society are clogging up the scientific training process. They have their career in mind, not scientific progress.

He was defense secretary and had a PhD. She is chancellor and has a PhD.

This leads to unintended consequences. A year ago, the German defense secretary (Dr) zu Guttenberg was about to lose his PhD title for plagiarism and consequently stepped down. Now, the German science minister (Prof. Dr) Schavan was forced to resign for the same reason. In between, a list of other German politicians was also found out. When prestige is more important than scientific value, the latter will obviously suffer. In this context the list of people with faulty PhDs at the highest levels of politics is hardly surprising.

What needs to change is a view that people with a PhD are somehow better people. At heart, a PhD is just a vocational qualification for science, a necessary step for pursuing a career in research or academia. It says nothing about the general quality of a person, or as Chris Chambers put it: ‘almost everyone who starts a PhD and sticks around long enough ends up getting one’. Of course you learn transferable skills while doing a PhD, but this does not mean that a PhD should be seen as a condition for having a business or politics career.

Paradoxically, everyone involved might actually benefit from less prestigious academic titles in the long run. Professors would be less bothered by PhD students who are not interested in research. The research literature would be less clogged up with easily obtained but uninteresting findings. And career minded graduates would not be required to spend years of their lives developing research skills which will perhaps not be needed in their later business or politics careers.

Now, how do you reduce the prestige of academic titles? There is no better way than to expose people in power who obtained them without actually deserving them. Thanks Dr zu Guttenberg and Prof. Dr Schavan.

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Figures:

1) via stabroeknews.com

2) By Bundeswehr-Fotos [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons

Are some languages easier than others? April 24, 2013

‘Long time no see’ is something I heard repeatedly in Britain even though it totally violates all the English grammar I learned at school. Clearly, Brits should correct this expression originating from Chinese Pidgin English rather than adopt it. The reason it entered common usage anyway is at the heart of why you might find English a lot easier to learn than the other British languages like Welsh or Gaelic. In a nutshell: when you learn English, it learns something from you as well.

Three years ago Gary Lupyan and Rick Dale published a (freely available) paper in which they looked at over 2,000 languages across the globe and quantified how difficult they are, e.g. by looking at their morphological complexity. Morphological complexity refers to how difficult it is to say a word in its correct form (‘went’ rather than ‘go-ed’). Its simpler counterpart is usually the use of more words to say the same thing (compare the sometimes irregular past like ‘gone’ with the always regular future ‘will go’). Using these principles Lupyan and Dale could show that languages which are spoken by more people tend to be simpler. Why?

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When languages grow big, they tend to get simple.

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Lupyan and Dale hypothesise that languages with more speakers also include more people who learned it when they were no longer children. As an adult, when you are not that good at learning a language anymore, you make yourself understood without speaking perfectly. Over time, these mistakes and simplifications are adopted by the language simply because difficult things never get learned by a new generation of learners. They are just forgotten. In some sense, the language learns what it can expect from its learners and what not. This drive towards simplification is a lot less strong when only expert language learners, i.e. children, are responsible for language transmission.

This year, a new study got published which directly looked at the proportion of adult second language learners in a given community rather than just assume it from the community size, as Lupyan and Dale did. Christian Bentz and Bodo Winter looked at case marking which is another pain to learn. In many languages around the world the Who does What to Whom pattern is not expressed through word order, like in English, but instead through case marking on words (similar to difference in roles marked by ‘he – him – his’). It turns out that on average languages which managed to retain a case system only have 16% of its speakers learn it after childhood, while the comparable number for no-case languages is 44%. Adults are bad at learning grammatical case systems, so it is forgotten if many adult learners speak the language.

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His forebearers shaped English. As does he.

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So, yes, some languages are indeed easier. Learning them is a lot simpler. The reason being that language is not an invention of a single person. Instead, it is a communication tool shaped by the people using it. When Chinese people started using English they made many mistakes, some of them got adopted like ‘Long time no see’. Notice how it uses very little morphology, i.e. the words are all like you would find them in a dictionary, and no case at all (by that time English no longer had a full case system).

Follow the path of other adult language learners and you will meet with less resistance.

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Bentz C, & Winter B (2013). Languages with more second language learners tend to lose case Language Dynamics and Change, in press

Lupyan G, & Dale R (2010). Language structure is partly determined by social structure. PloS one, 5 (1) PMID: 20098492

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Figures:

1) adapted from Lupyan & Dale, 2010, p. 7

2) By Eneas De Troya from Mexico City, México (Melting Pot  Uploaded by russavia) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons

The biological basis of orchestra seating March 28, 2013

Many cultural conventions appear like the result of historical accidents. The QWERTY – keyboard is a typical example: the technical requirements of early typewriters still determine the computer keyboard that I write this text on, even though by now technical advances would allow for a far more efficient design. Some culturally accepted oddities, however, appear to reflect the biological requirements of human beings. The way musicians are seated in an orchestra is one such case, but the listener is, surprisingly, not the beneficiary.

When one goes to a concert one typically sees a seating somewhat like the one below: strings in the front, then woodwinds further back, then brass. What is less obvious is that, in general, higher pitched instruments are seated on the left and lower pitched instruments on the right. The strings show this pattern perfectly: from left to right one sees violins, violas, cellos and then basses. Choirs show the same pattern: higher voices (soprano and tenor) stand left of the lower voices (alt and basses). Why is that?

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An orchestra I have personally performed with.

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It turns out that this is not a historical accident but instead a biological requirement. Diana Deutsch has used a series of audio illusions which all showed a curious pattern: when you present two series of tones each to one ear, you have the illusion that the high tones are being played to your right ear and the low ones to the left ear. In case you don’t believe me, listen to this illustration of Deutsch’s scale illusion:

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Apparently, there is a right ear advantage for high tones. So, seating the higher instruments on the left side (as seen on the photo) makes complete sense as this way musicians on stage tend to hear higher tones coming from their right. However, from the point of view of the audience this is actually a really bad idea as their right ear advantage is not taken into account. It turns out that orchestra seating arrangements are not favouring the hearing of the audience or the conductor but instead the musicians!

The right ear advantage for high tones is even mirrored in musicians’ brains. We know that the right ear projects mostly to the left auditory cortex and vice versa for the left ear. So, one would expect that people who play high instruments have trained their right ear / left auditory cortex the most when they practiced their craft. These training effects should be mirrored in differences in cortex size. This would mean that people sitting on the left in an orchestra have bigger left auditory cortices. In a fascinating article Schneider and colleagues showed that by and large this is the case: professional musicians who play high instruments or instruments with a sharp attack (e.g., percussionists, piano players) tend to have greater left auditory cortices than right auditory cortices. Their figure says is all.

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How the brains are seated in an orchestra.

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The orchestra seating arrangement mirrors not only the listening biases of most human ears but on top of that the brain differences between musicians. By and large, the orchestra is organised according to biological principles. Thus, not all cultural conventions – like the seemingly arbitrary seating arrangement of orchestras – have their roots in historical accidents. Cultural oddities are sometimes merely down to biology.

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Deutsch, D. (1999). Grouping Mechanisms in Music The Psychology of Music, Second Edition, 299-348 DOI: 10.1016/B978-012213564-4/50010-X

Schneider P, Sluming V, Roberts N, Bleeck S, & Rupp A (2005). Structural, functional, and perceptual differences in Heschl’s gyrus and musical instrument preference. Annals of the New York Academy of Sciences, 1060, 387-94 PMID: 16597790

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Figures:

1) Nederlands: Symfonieorkest Nijmegen in de grote zaal van de Vereeniging, The SON photo library, via wikimedia

2) as found in Schneider et al., 2005, p. 392

What lies behind the mystery of being born with a phantom penis? January 22, 2013

This is nothing compared to what the mind does with us every day.

Like a magician our mind tricks us into believing what we see and feel. We only notice that something strange is going on when our expectations are betrayed during the prestige – when the white rabbit is drawn out of the empty hat. Psychology sometimes works in much the same way. After the mind has made us believe in the ordinary, it creates strange cases which point to something bigger going on behind the scenes. One of the most extraordinary illusions is the one of our body. At the final prestige we see people born with phantom penises which no one can see. What was going on behind the scenes?

‘Phantoms’ is what Silas Weir Mitchell called the amputated limbs that their owners could still feel. The most straight-forward explanation simply refers to re-membering. When an amputated limb lives on as a phantom arm one could say that the mind fails to realise the loss and fills in the usual feelings with memories. This re-membering may well explain why some people claim to feel a watch or even clothes on the phantom skin.

It is as if the magician had produced a rabbit out of an ‘empty’ hat and everyone suddenly noticed that the hat was high enough to house it from the start. However, the mind had another trick up its sleeve. Since the initial description of phantom limbs in 19^th century amputees, this phenomenon has also been discovered in people who had never been born with limbs to begin with. These so called congenital phantom limbs are very strange because their owners obviously have no memories of limbs. Re-membering cannot explain this.

Perhaps it is time to turn from psychology to neuroscience in our quest to understand this trick. The part of the human brain responsible for limb movements is a well organised bit of cortex which looks very similar across people: the primary motor cortex. When the appropriate bit of my own primary motor cortex once got stimulated with magnetic waves, my index finger twitched. Peter Brugger and colleagues did the same with a woman only known as A.Z.. She was born without arms or legs but reported feeling them nonetheless. Magnetic stimulation of her primary motor cortex made her phantom limbs move. This suggests that the action control mechanism and the brain mechanism responsible for phantom limbs are linked.

Thus, all we know about action control in the human brain can be used to explain away the phantom limb phenomenon. Firstly, the primary motor cortex is at least partly genetically determined, i.e. limb control is part of our genetic make-up whether we’ve got limbs or not.  When trying to control limbs which do not exist, the brain may create the illusion of controlling phantom limbs instead. Secondly, some researchers believe that a muscle activation command is not only sent to the muscles but a copy is also sent to the back of the brain. This allows us to react to expected action outcomes even before they have occurred. Phantom limbs may occur because expected actions get misinterpreted as real ones. Thirdly, mirror neurons code for actions seen and actions done. According to this explanation A.Z. saw many people use their limbs and this made her have the illusion that she could do the same, albeit only with phantom limbs instead of real ones.

A Greek statue depicting phantom limbs.

However, the final prestige defies all these explanations. Something else entirely must be responsible for a phenomenon reported by Vilayanur Ramachandran and Paul McGeoch in 2008: phantom penises. Like phantom limbs they can occur after amputation. Fascinatingly though, they were also reported by female-to-male transsexuals without an artifical penis. Crucially, this cannot simply be put away as ‘wishful thinking’. For one, their phantom penises were not perfect: for some they were shaped in an undesirable way, erected in embarrassing non-erotic situations, or rubbing against the jeans. But more importantly, Western society goes to great lengths to make life as a transsexual seem like an unattractive option. For example, when they were children, two phantom penis owners were taken to a psychiatrist by their puzzled parents to be treated for a penis that did not exist. Why would anyone want to go through this as a child – or indeed through life changing surgery as an adult – if it wasn’t absolutely necessary?

But if being born with a phantom penis cannot be explained by re-membering, brain mechanisms of action control (a penis is obviously not a muscle one can voluntarily control), or wishful thinking – then what lies behind this phenomenon? This final trick of the mind, seemingly the most ordinary sensation of being a man or a woman in a male or female body, defies easy solutions. Ramachandran and McGeoch speculate that hormonal factors before birth could be responsible.

Before any such speculation can be substantiated I can only conclude that this final prestige remains a mystery. Just like an audience member seeing a magician do a trick on a member of the public, I wonder whether I have been tricked as well. Phantom limbs and phantom penises show powerfully that the link between our anatomical body and our body image is a fragile one. The mind is doing all sorts of trickery behind the scenes in order to hide this difference between body felt and body seen. Like with any good magician, one wonders how this trick is actually done.

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Brugger P, Kollias SS, Müri RM, Crelier G, Hepp-Reymond MC, & Regard M (2000). Beyond re-membering: phantom sensations of congenitally absent limbs. Proceedings of the National Academy of Sciences of the United States of America, 97 (11), 6167-72 PMID: 10801982

Mitchell, W (1871). Phantom limbs Lippinscott’s Magazine, 8, 563-569

Ramachandran, VS, & McGeoch, PD (2008). Phantom Penises In Transsexuals – Evidence of an Innate Gender-Specific Body Image in the Brain Journal of Consciousness Studies, 15 (1), 5-16

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If you like this post, you may also like:

Three fun ways to have three hands – for you at home

Pictures:

1) By Strobridge Litho. Co., Cincinnati & New York  Restoration by trialsanderrors and Morn via Wikimedia Commons

2) By Shawn Lipowski (Shawnlipowski) (Own work) via Wikimedia Commons

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delaying dementia without pills January 7, 2013

‘What’s this? A potato?’ asked my friend’s grandfather during lunch. As always, he used his charming grin and characteristically loud voice. Even though the entire conversation was in Argentine Spanish – which I had learned only a short while before – I understood the oddity of the situation at once. Instead of a potato, the grandfather held a kiwifruit in his hands.

After only a short time of living with this family I noticed that the grandfather no longer had the mental abilities he once must have possessed in order to lead a successful business and raise an adorable family. He was undiagnosed but his behaviour reminded me of Mild Cognitive Impairment, which can progress to a more severe general cognitive impairment – Alzheimer’s Disease or more generally dementia – which usually cannot be cured. ‘What can be done?’ I was asked by my friend’s grandmother afraid of slowly losing the husband she had shared most of her life with. In broken Spanish I tried to explain to her what I would do: build up a cognitive reserve. This concept – related to the beneficial effects of, for example, high education or mentally demanding spare time activities – is perhaps the most promising strategy for delaying dementia.

A large scale analysis illustrates what a cognitive reserve can achieve. First of all, it can delay dementia. An Australian research team (Valenzuela & Sachdev, 2006) collected studies which recruited old people when they were still perfectly healthy and then tested them again after a few years to find out by how much their cognitive abilities had declined. The trend across more than 47,000 people was for higher education and more demanding leisure activities to slow down the creeping loss of mental abilities leading to dementia.

A German nun without experimental confounds.

The savvy reader may already notice a problem with this theory: high education is associated with a generally healthier lifestyle. Rather than cognitive reserve, we should perhaps simply be talking about healthy vs. non-healthy life styles. A Bavarian study ruled this problem out (Bickel & Kurz, 2009). They gained access to the education and dementia records of older female members of a religious order who lived as similarly as one can imagine. The 442 participants had shared a roof for more than five decades, shared meals together, had the same access to medical care. None smoked. None had any personal items. And still, 39% of sisters with low education suffered from dementia, compared to only 14% in the remaining group. Clearly, whether life style has an effect or not, the benefits of a cognitive reserve cannot be reduced to it. It delays dementia all by itself.

This beneficial effect of a cognitive reserve led me to give my advice. However, this strategy cannot stave off dementia forever or even slow it down once it kicks in. Nikolaos Scarmeas and colleagues from Columbia University (2006) found that more highly educated New Yorkers above 65 lose their memory faster around the time of an Alzheimer’s disease diagnosis compared to less educated city dwellers. Apparently, the benefits of a high education are absent around the time of diagnosis.

This raises the obvious question whether my advice was perhaps too late. Once on the road to Alzheimer’s there may be no turning back and efforts to delay the inevitable could make things worse. Given what we know about how the cognitive reserve actually works, I do not believe that this is true. First of all, a cognitive reserve is no cure against dementia but merely a way to delay it. The theory goes that brain pathology progresses whether you have a cognitive reserve or not. What a high education level and demanding leisure activities actually do is to avoid the usual outcome of brain pathology – e.g., easily noticeable memory problems of the kind I have described above. This is supported by studies which compared the brains of people with equal mental function in high age. Those with higher education have more amyloid deposits – a peptide associated with Alzheimer’s disease – as if they were able to deal with their reduced brain function in a better way (Kemppainen et al., 2008; Rentz et al., 2010). At some point though, the progressively worse brain function catches up with you and the resulting cognitive decline is faster.

Charles Hall and colleagues (2007; 2009) tested this overall model in the real world. His analyses of memory test scores of over 100 Bronx residents over the years shows the predicted trend. At first, a high cognitive reserve – whether education or leisure activities – delays the point in time when mental abilities suddenly decline rapidly. Each year in education delays this moment by two and a half months. Each day of mentally stimulating leisure activities delays it by two months. Once this moment is reached, though, the decline is faster with a higher cognitive reserve – as if the aforementioned brain pathology catches up. A cognitive reserve helps you to delay dementia but not to escape it.

The higher the education the shallower the decline before a break point, the later that break point, and the steeper the decline thereafter.

My friend’s grandfather had long been out of education. But the second source of a cognitive reserve – mentally demanding leisure activities – was not beyond him. What sort of activities work? A French research team led by Tasnime Akbaraly (2009) took a better look. They found that only a certain kind of leisure activity will delay dementia onset. Watching television and other passive behaviours won’t do. Neither do physical activities like going for a walk. Nor social ones like have friends or family over. The crucial set of activities are the mentally demanding ones: doing crosswords, playing cards, attending organisations, going to the cinema/theatre, practicing an artistic activity etc.

It is a mystery to me why this knowledge is not more widely spread. Dementia is one of the central challenges facing an ageing population as well as many old couples individually. Research shows that one does not need to be a passive spectator of mental decline. If a cognitive reserve has been built up, one can enjoy more years without showing signs of an incurable disease. That’s what I tried to say in broken Spanish to my friend’s grandmother: make him use his mind.

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Akbaraly, T., Portet, F., Fustinoni, S., Dartigues, J., Artero, S., Rouaud, O., Touchon, J., Ritchie, K., & Berr, C. (2009). Leisure activities and the risk of dementia in the elderly: Results from the Three-City Study Neurology, 73 (11), 854-861 DOI: 10.1212/WNL.0b013e3181b7849b

Bickel H, & Kurz A (2009). Education, occupation, and dementia: the Bavarian school sisters study. Dementia and geriatric cognitive disorders, 27 (6), 548-56 PMID: 19590201

Hall CB, Derby C, LeValley A, Katz MJ, Verghese J, & Lipton RB (2007). Education delays accelerated decline on a memory test in persons who develop dementia. Neurology, 69 (17), 1657-64 PMID: 17954781

Hall CB, Lipton RB, Sliwinski M, Katz MJ, Derby CA, & Verghese J (2009). Cognitive activities delay onset of memory decline in persons who develop dementia. Neurology, 73 (5), 356-61 PMID: 19652139

Kemppainen NM, Aalto S, Karrasch M, Någren K, Savisto N, Oikonen V, Viitanen M, Parkkola R, & Rinne JO (2008). Cognitive reserve hypothesis: Pittsburgh Compound B and fluorodeoxyglucose positron emission tomography in relation to education in mild Alzheimer’s disease. Annals of neurology, 63 (1), 112-8 PMID: 18023012

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Scarmeas, N., Albert, S.M., Manly, J.J., & Stern, Y. (2005). Education and rates of cognitive decline in incident Alzheimer’s disease Journal of Neurology, Neurosurgery & Psychiatry, 77 (3), 308-316 DOI: 10.1136/jnnp.2005.072306

Valenzuela MJ, & Sachdev P (2006). Brain reserve and cognitive decline: a non-parametric systematic review. Psychological medicine, 36 (8), 1065-73 PMID: 16650343

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Figures:

1) By André Karwath aka Aka (Own work) [CC-BY-SA-2.5 (http://creativecommons.org/licenses/by-sa/2.5)%5D, via Wikimedia Commons

2) By Doris Ulmann, 1882–1934. [Public domain], via Wikimedia Commons

3) Hall et al., 2007, p. 1661

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