genes

Gender Differences

In general, males are better at spatial tasks involving mental rotation.

In general, females have superior verbal skills.

Males are far more likely to pursue math or science careers, but gender differences in math are not consistent across nations or ages.

A number of imaging studies have demonstrated that the brains of males and females show different patterns of activity on various tasks.

Nicotine has been shown to differentially alter men's and women's brain activity patterns so that the differences disappear.

Both estrogen and testosterone have been shown to affect cognitive function.

Training has been shown to bring parity to differences in cognitive performance between the sexes.

Age also alters the differences between men and women.

Widely cited gender differences in cognition

It is clear that there are differences between the genders in terms of cognitive function; it is much less clear that there are differences in terms of cognitive abilities. Let me explain what I mean by that.

It's commonly understood that males have superior spatial ability, while females have superior verbal ability. Males are better at math; females at reading. There is some truth in these generalizations, but it's certainly not as simple as it is portrayed.

First of all, as regards spatial cognition, while males typically outperform females on tasks dealing with mental rotation and spatial navigation, females tend to outperform males on tasks dealing with object location, relational object location memory, and spatial working memory.

While the two sexes score the same on broad measures of mathematical ability, girls tend to do better at arithmetic, while boys do better at spatial tests that involve mental rotation.

Having said that, it does depend where you're looking. The Programme for International Student Assessment (PISA) is an internationally standardised assessment that is given to 15-year-olds in schools. In 2003, 41 countries participated. Given the constancy of the gender difference in math performance observed in the U.S., it is interesting to note what happens in other countries. There was no significant difference between the sexes in Australia, Austria, Belgium, Japan, the Netherlands, Norway, Poland, Hong Kong, Indonesia, Latvia, Serbia, and Thailand. There was a clear male superiority for all 4 content areas in Canada, Denmark, Greece, Ireland, Korea, Luxembourg, New Zealand, Portugal, the Slovak Republic, Liechtenstein, Macao and Tunisia. In Austria, Belgium, the United States and Latvia, males outperformed females only on the space and shape scale; in Japan, the Netherlands and Norway only on the uncertainty scale. And in Iceland, females always consistently do better than males!

Noone knows why, but it is surely obvious that these differences must lie in cultural and educational factors.

Interestingly, the IEA Third International Mathematics and Science Study (TIMSS) shows this developing -- while significant gender differences in mathematics were found only in 3 of the 16 participating OECD countries for fourth-grade students, gender differences were found in 6 countries at the grade-eight level, and in 14 countries at the last year of upper secondary schooling.

This inconsistency is not, however, mirrored in verbal skills -- girls outperform boys in reading in all countries.

Gender differences in language have been consistently found, and hardly need reiteration. However, here's an interesting study: it found gender differences in the emerging connectivity of neural networks associated with skills needed for beginning reading in preschoolers. It seems that boys favor vocabulary sub-skills needed for comprehension while girls favor fluency and phonic sub-skills needed for the mechanics of reading.The study points to the different advantages each gender brings to learning to read.

There's a lesson there.

There are other less well-known differences between the sexes. Women tend to do better at recognizing faces. But a study has found that this superiority applies only to female faces. There was no difference between men and women in the recognition of male faces.

Moreover, pre-pubertal boys and girls have been found to be equally good at recognizing faces and identifying expressions. However, they do seem to do it in different ways. Boys showed significantly greater activity in the right hemisphere, while the girls' brains were more active in the left hemisphere. It is speculated that boys tend to process faces at a global level (right hemisphere), while girls process faces at a more local level (left hemisphere).

It's also long been recognized that women are better at remembering emotional memories. Interestingly, an imaging study has revealed that the sexes tend to encode emotional experiences in different parts of the brain. In women, it seems that evaluation of emotional experience and encoding of the memory is much more tightly integrated.

But of course, noone denies that there are differences between men and women. The big question (one of the big questions) is how much, if any, is innate.

Studies of differences, even at the neural level, don't demonstrate that. It's increasingly clear that environmental factors affect all manner of thing at the neural level. However, one study of 1-day-old infants did find that boys tended to gaze at three-dimensional mobiles longer than girls did, while girls looked at human faces longer than boys did.

Of course, even a 1-day-old infant isn't entirely free of environmental influence. In this case, the most important environmental influence is probably hormones.

Hormones and chemistry

A lot of studies in recent years have demonstrated that estrogen is an important player in women's cognition. Spatial ability in particular seems vulnerable to hormonal effects. Women do vary in their spatial abilities according to where they are in the menstrual cycle, and there is some evidence that spatial abilities (in both males and females) may be affected by how much testosterone is received in the womb.

Another study has found children exposed to higher levels of testosterone in the womb also develop language later and have smaller vocabularies at 2 years of age.

Hormones aren't the only chemical affecting male and female brains differently. Significant differences have been found in the brain activity of men and women when engaged in a broad range of activities and behaviors. These differences are more acute during impulsive or hostile acts. But — here's the truly fascinating thing — nicotine causes these brain activity differences to disappear. A study has found that among both smokers and non-smokers on nicotine, during aggressive moments, there are virtually no differences in brain activity between the sexes. A finding that supports other studies that indicate men's and women's brains respond differently to the same stimuli — for example, alcohol.

What does all this mean? Well, let's look at the question that's behind the whole issue: are men smarter than women? (or alternately, are women smarter than men?)

Is one sex smarter than the other?

Here's a few interesting studies that demonstrate some more differences between male and female brains.

A study of some 600 Dutch men and women aged 85 years found that the women tended to have better cognitive speed and a better memory than the men, despite the fact that significantly more of the women had limited formal education compared to the men. This may be due to better health. On the other hand, there do appear to be differences in the way male and female brains develop, and the way they decline.

For example, women have up to 15% more brain cell density in the frontal lobe, which controls so-called higher mental processes, such as judgement, personality, planning and working memory. However, as they get older, women appear to shed cells more rapidly from this area than men. By old age, the density is similar for both sexes.

A study of male and female students (aged 18-25) has found that men's brain cells can transmit nerve impulses 4% faster than women's, probably due to the faster increase of white matter in the male brain during adolescence.

An imaging study of 48 men and women between 18 and 84 years old found that, compared with women, men had more than six times the amount of intelligence-related gray matter. On the other hand, women had about nine times more white matter involved in intelligence than men did. Women also had a large proportion of their IQ-related brain matter (86% of white and 84% of gray) concentrated in the frontal lobes, while men had 90% of their IQ-related gray matter distributed equally between the frontal lobes and the parietal lobes, and 82% of their IQ-related white matter in the temporal lobes. Despite these differences, men and women performed equally on the IQ tests.

It has, of course, long been suggested that women are intellectually inferior because their brains are smaller. A study involving the intelligence testing of 100 neurologically normal, terminally ill volunteers found that a bigger brain size is indeed correlated with higher intelligence — but only in certain areas, and with odd differences between women and men. Verbal intelligence was clearly correlated with brain size for women and — get this — right-handed men! But not for left-handed men. Spatial intelligence was also correlated with brain size in women, but much less strongly, while it was not related at all to brain size in men.

Also, brain size decreased with age in men over the age span of 25 to 80 years, suggesting that the well-documented decline in visuospatial intelligence with age is related, at least in right-handed men, to the decrease in cerebral volume with age. However age hardly affected brain size in women.

What is all this telling us?

Male and female brains are different: they develop differently; they do things differently; they respond to different stimuli in different ways.

None of this speaks to how well information is processed.

None of these differences mean that individual brains, of either sex, can't be trained to perform well in specific areas.

Here’s an experiment and a case study which bear on this.

It's all about training

The experiment concerns rhesus monkeys. The superiority of males in spatial memory that we're familiar with among humans also occurs in this population. But here's the interesting thing — the gender gap only occurred between young adult males and young untrained females. In other words, there was no difference between older adults (because performance deteriorated with age more sharply for males), and did not occur between male and female younger adults if they were given simple training. Apparently the training had little effect on the males, but the females improved dramatically.

The “case study” concerns Susan Polgar, a chess master. You can read about her in a recent article (http://www.opinionjournal.com/la/?id=110006356 ), which I noticed because the Polgar sisters are a well-known example of “hot-housing”. I cited them in my own article on the question of whether there is in fact such a thing as innate talent. Susan Polgar and her sisters are examples of how you can train “talent”; indeed, whether there is in fact such a thing as “talent” is a debatable question. Certainly you can argue for a predisposition towards certain activities, but after that … Well, even geniuses have to work at it, and while you may not be able to make a genius, you can certainly create experts.

This article was provoked, by the way, by comments by the President of Harvard University, Lawrence Summers, who recently stirred the pot by giving a speech arguing that boys outperform girls on high school science and math scores because of genetic differences between the genders, and that discrimination is no longer a career barrier for female academics. Apparently, during Dr Summers' presidency, the number of tenured jobs offered to women has fallen from 36% to 13%. Last year, only four of 32 tenured job openings were offered to women.

You can read a little more about what Dr Summers said at http://education.guardian.co.uk/gendergap/story/0,7348,1393079,00.html, and there's a rather good response by Simon Baron-Cohen (professor in the departments of psychology and psychiatry, Cambridge University, and author of The Essential Difference) at: http://education.guardian.co.uk/higher/research/story/0,9865,1399109,00.html

Parts of this article originally appeared in the January and February 2005 newsletters.

References: 
  • Canli, T., Desmond, J.E., Zhao, Z. & Gabrieli, J.D.E. 2002. Sex differences in the neural basis of emotional memories. Proceedings of the National Academy of Sciences, 99, 10789-10794.
  • Everhart, D.E., Shucard, J.L., Quatrin, T. & Shucard, D.W. 2001. Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children. Neuropsychology, 15(3), 329-341.
  • Fallon, J.H., Keator, D.B., Mbogori, J., Taylor, D. & Potkin, S.G. 2005. Gender: a major determinant of brain response to nicotine. The International Journal of Neuropsychopharmacology, 8(1), 17-26. (see http://www.eurekalert.org/pub_releases/2005-02/uoc--bao021705.htm)
  • Geary, D.C. 1998. Male, Female: The Evolution of Human Sex Differences. Washington, D.C.: American Psychological Association.
  • Haier, R.J., Jung, R.E., Yeo, R.A., Head, K. & Alkire, M.T. 2005. The neuroanatomy of general intelligence: sex matters. NeuroImage, 25(1), 320-327.
  • Hanlon, H. 2001. Gender Differences Observed in Preschoolers’ Emerging Neural Networks. Paper presented at Genomes and Hormones: An Integrative Approach to Gender Differences in Physiology, an American Physiological Society (APS) conference held October 17-20 in Pittsburgh.
  • Kempel, P.. Gohlke, B., Klempau, J., Zinsberger, P., Reuter, M. & Hennig, J. 2005. Second-to-fourth digit length, testosterone and spatial ability. Intelligence, 33(3), 215-230.
  • Lacreuse, A., Kim, C.B., Rosene, D.L., Killiany, R.J., Moss, M.B., Moore, T.L., Chennareddi, L. & Herndon, J.G. 2005. Sex, age, and training modulate spatial memory in the Rhesus monkey (Macaca mulatta). Behavioral Neuroscience, 119 (1).
  • Levin, S.L., Mohamed, F.B. & Platek, S.M. 2005. Common ground for spatial cognition? A behavioral and fMRI study of sex differences in mental rotation and spatial working memory. Evolutionary Psychology, 3, 227-254.
  • Lewin, C. & Herlitz, A. 2002. Sex differences in face recognition-Women's faces make the difference, Brain and Cognition, 50 (1), 121-128.
  • OECD. Learning for Tomorrow's World –First Results from PISA 2003 http://www.oecd.org/document/0/0,2340,en_2649_201185_34010524_1_1_1_1,00.html
  • Reed, T.E., Vernon, P.A. & Johnson, A.M. 2005. Confirmation of correlation between brain nerve conduction velocity and intelligence level in normal adults. Intelligence, 32(6), 563-572.
  • van Exel, E., Gussekloo, J., de Craen, A.J.M, Bootsma-van der Wiel, A., Houx, P., Knook, D.L. & Westendorp, R.G.J. 2001. Cognitive function in the oldest old: women perform better than men. Journal of Neurology, Neurosurgery & Psychiatry, 71, 29-32.
  • Witelson, S.F., Beresh, H. & Kigar, D.L. 2006. Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors. Brain, 129, 386-398.
  • Witelson, S.F., Kigar, D.L. & Stoner-Beresh, H.J. 2001. Sex difference in the numerical density of neurons in the pyramidal layers of human prefrontal cortex: a stereologic study. Paper presented to the annual Society for Neuroscience meeting in San Diego, US.

The question of innate talent

Some personal experience

I have two sons. One of them was a colicky baby. Night after night my partner would carry him around the room while I tried to get a little sleep. One night, for his own amusement, my partner chose a particular CD to play. Magic! As the haunting notes of the hymns of the 12th century abbess Hildegard of Bingen rang through the room, the baby stopped crying. And stayed stopped. As long as the music played. Experimentation revealed that our son particularly liked very early music (plainchant from the 15th century Josquin des Pres was another favorite).

We felt sorry for all those parents with crying babies who hadn't discovered this magic cure-all.

And then we had another son.

This one didn't like music. No magic this time. And we realized, it wasn't that 12th century music had magical properties to calm a crying baby. No, it was this particular baby that responded to this sort of music.

The years went on. Nothing we saw contradicted that first impression - one son was "musical", and one was not. It seemed pretty clear to us. One son took after me, and one took after my partner.

My partner plays the piano, and the pipe organ, and the harpsichord. He is "into" Bach. He has played in churches and concerts. He has a shelf full of books on music and cupboards full of music scores, CDs by the score.

Me? I like to sing, to myself. I learned the violin for a while in my youth. I like to listen to CDs of jazz, and popular show tunes. I like music, but I'm not sophisticated about it. It's background to me. My partner actually listens to it.

So which child took after which parent?

Well, we believe the "musical" one took after me, and the "non-musical" one took after my partner. Because - he got there by training. By practicing and learning and persevering and taking an interest. He has no sense of rhythm, no particularly keen sense of pitch. But he's the one who can produce music. Me, I have an ear for music. Remembering a rhythm is effortless for me; I respond, instinctively, to music. But I could never bother to practice, and my response to music has stayed at the same level. Instinctive.

Our "musical" son has been involved in learning music the Suzuki way since he was four. We never particularly encouraged our other son to do likewise, simply told him he could if he wanted to. His brother persuaded him he did want to. So, fine, we said.

You can guess, I'm sure, how things have been. It's been obvious, watching and listening to our older son, that he has a talent for music, that it comes easily to him. Equally obvious that it hasn't come that easily to our younger son. But it's the younger son who has made much faster progress in the past year, because he practices more, because he's keen to learn. And it's been amazing to watch his ear for music develop.

Do you need an inborn talent to do well?

Suzuki flew in the face of "common-sense" when he decided very young children with no demonstrable genius could be taught to play the violin. I can only imagine the stunned amazement with which the first Suzuki concerts were greeted. They still amaze today.

Suzuki himself, while he supported the training of all children, believed that, of course, some would be "naturally" gifted, and that outstanding performance would require a gift, as well as training. However, as his experience with children and his method increased, he grew to believe that “every child can be highly educated if he is given the proper training” and blamed early training failures on incorrect methods. More about Suzuki

Howard Gardner (inventor of the Multiple Intelligences theory) reviewed the exceptional music performance attained by children trained in the Suzuki method, and noted many of these children, who displayed no previous signs of musical talent, attained levels comparable to music prodigies of earlier times. Therefore, he concluded, the important aspect of talent must be the potential for achievement and the capacity to rapidly learn material relevant to one of the intelligences. That is, since we didn't see the talent before we started training, and since the fact that they do perform so well demonstrates that they must have talent, then the talent must have existed in potential.

This is, of course, a wholly circular argument.

And one that is widely believed. According to an informal British survey, more than ¾ of music educators believe children can’t do well unless they have special innate gifts10. It is believed that saying that someone has a “gift” for something explains why they have excelled at something - although it is an entirely circular argument: Why do they do well? Because they have a gift. How do you know they have a gift? Because they do well.

It is also widely believed that such innate talents can be detected in early childhood.

The problem with this view is that many children are denied the opportunities and support to achieve excellence, because it has been decreed that they don’t “have” an appropriate talent.

The circular argument becomes truly a vicious circle. You don't do this easily first time, therefore you don't have any talent, therefore it's not worth pushing you to do well, therefore you won't do well - which proves what we told you in the first place, you have no talent!

So how much justification is there for believing excellence requires a "natural" talent?

Is there such a thing as inborn talent?

A questionnaire study found that early interest and delight in musical sounds fails to predict later musical competence25.

We have all heard stories of child prodigies who supposedly could do amazing things from a very young age. In no case however, is this very early explosion of skills (in the first three years) observed directly by an impartial observer – the accounts all being (naturally enough you might think), retrospective and anecdotal. Noone denies that very young children, from 3 years old, have been observed to have remarkable skills for their age, but although the parents typically say the child learned these skills entirely unaided, this is not supported by the evidence. For example, in a typical case, the parents claimed (and no doubt sincerely believed) that their child learned to read entirely unaided and that they only discovered this on seeing her reading Heidi. However they had kept detailed records of her accomplishments. As Fowler19 pointed out, it is difficult to believe that parents who keep such accounts have not been actively involved in the child’s early learning.

Music is an area where infant prodigies abound – many famous composers are reported to have displayed unusual musical ability at a very young age. Again, however, such accounts are reported many years later (after the composer has become famous). Early biographies of prominent composers reveal they all received intensive and regular supervised practice sessions29. “The emergence of unusual skills typically followed rather than preceded a period during which unusual opportunities were provided, often combined with a strong expectation that the child would do well."

Art is another area where infant "geniuses" are occasionally cited. However, although some 2 and 3 year olds have produced drawings considerably more realistic than is the norm45, among major artists, few are known to have produced drawings that display exceptional promise before age 8 or so44.

There is no doubt that some individuals acquire some skills more easily than others, but this doesn’t necessarily have anything to do with 'talent'. Motivational and personality factors, as well as previous learning experiences, can all affect such facility.

Biological factors that might underlie "talent"

There are various underlying factors that are at least partly genetic and no doubt influence ability – for example response speed2 and working memory capacity8,9 - but there is no clear neural correlate for any specific exceptional skill.

The closest such correlate is that of "perfect" pitch. There does appear to be a structural difference in the brain of those who have absolute pitch, and certainly some young children have been shown to have perfect pitch. However, even if this difference in the brain is innate and not, as it could well be, the result of differences in learning or experience, having perfect pitch is no guarantee that you will excel at music. Moreover, it appears that it can be learned. It’s relatively common in musicians given extensive musical training before five or six12, and even appears to be learnable by adults, although with considerably more difficulty3,42.

It is always difficult to demonstrate that an observed neurological or physical difference is innate rather than the product of training or experience. For example, many people have pointed to particular physical features as being the reason for particular sports people to excel at their particular sport. However, while individual differences in the composition of certain muscles are reliable predictors of differences in athletic performance, the differences in the proportion of the slow-twitch muscle fibres that are essential for success in long-distance running, for example, are largely the result of extended practice, rather than the cause of differential ability11. Differences between athletes and others in the proportions of particular kinds of muscle fibres are specific to those muscles that are most fully exercised in the athletes’ training22.

There is little evidence, too, for the idea that exceptional athletes are born with superior motor and perceptual abilities. Tests for basic motor and perceptual abilities fail to predict performance15. Exceptional sportspeople do not reliably score higher than lesser mortals on such basic tests.

Savants

So-called idiot-savants are widely cited in support of the idea of innate talent. However, studies of cases have found the opportunities, support and encouragement for learning the skill have preceded performance by years or even decades12,23,43. Moreover, their skills are learnable by others.

The only ability that can’t be reproduced after brief training is the reputed ability to reproduce a piece of music after a single hearing. However, in a study of one such savant5 it was shown that such reproduction depended on the familiarity of the sequences of notes. Tonally unconventional pieces were remembered poorly. Thus, musical savants, like normal experts, need access to stored patterns and retrieval structures to enable them to retain long, unfamiliar musical patterns.

Predicting adult performance

Several interview and biographical studies of exceptional people have been carried out (e.g., pianists40,41; musicians31; tennis players35; artists37; swimmers26; mathematicians20). In no case could you have predicted their eventual success from their early childhood behavior; few showed signs of exceptional promise prior to receiving parental encouragement.

Composers21, chess players36, mathematicians20, sportspeople26,32 have all been shown to require many years of sustained practice and training to reach high levels of expertise.

Twin studies

Twin studies support the view that family experience is more important than genes for the development of specific abilities (e.g., The Minnesota Study of Twins Reared Apart found self-ratings of musical talent correlated .44 among identical twins reared apart, compared to .69 for identical twins reared together30; correlations on a number of measures of musical ability were not much lower for fraternal twins (.34 to .83) than for identical twins (.44 to .9)7.

Moreover, the importance of inherited factors reduces as training and practice increases1,28,15.

Practice and performance level

The performance level of student violinists in their 20s is strongly correlated with the number of hours that they practiced13,14. Similarly with pianists27. No significant differences have been found between highly successful young musicians and other children in the amount of practice time they required to make a given amount of progress between successive grades in the British musical board exams; achieving the highest level (grade 8) required an average of some 3300 hours of practice regardless of the ability group to which the student had been assigned39. Another study found that by age 20, the top-level violinists had practiced an average of more than 10000 hrs, some 2500 hrs more than the next most accomplished group15.

Practice accounts for far more than most of us might realize. Several studies have demonstrated the high levels of performance (often higher than experts had regarded as possible) that can be attained by perfectly ordinary adults, given enough practice4,6,12.

It has been argued that talent encourages children to practice more, but this is contradicted by the finding that, even among highly successful young musicians, most admit they would never have regularly practiced at the required level without strong parental encouragement38,24.

The top of the cream?

It may well be, of course, that there is a quality to the exceptionally talented person’s performance that is missing from others, however hard they have practiced.

It is also possible that, although practice, training, and other influences may account for performance differences in most people, there is a small number of people to whom this doesn’t apply.

However, there is at this time no evidence that this is true.

What is clear is that “no case has been encountered of anyone reaching the highest levels of achievement in chess-playing, mathematics, music, or sports without devoting thousands of hours to serious training” (Howe et al 1999).

The pattern of learning seems to be the same for everyone, arguing against some qualitative difference between "geniuses" and ordinary folk. Studies of prodigies in chess and music show that the skills are acquired in the same manner by everyone, but that prodigies reach higher levels faster and younger16,17. Moreover, rather than acquiring their skills in a vacuum, it appears that “the more powerful and specific the gift, the more need for active, sustained and specialized intervention” (Feldman, 1986, p123).

The producing of an outstanding talent indeed, seems to require a great deal of parental support and early intervention.

It is particularly instructive to observe the case of the Polgar daughters. With no precocious love for the chess board observable in their three daughters, Laslo & Klara Polgar, simply as an educational experiment, decided to raise their daughters to be chess experts. All did extraordinarily well, and one became the youngest international chess grand master ever18.

It has been noted that the performance of experts of yesteryear is now attainable by many. When Tchaikovsky asked two of the greatest violinists of the day to play his violin concerto, it is said, they refused, deeming it unplayable33 - now it is standard repertoire for top violinists. Paganini, it is claimed, would cut a sorry figure on a concert stage today34. Such is the standard we have come to expect from our top performers.

And we are all familiar with the way sports records keep being broken – the winning time for the 1st Olympic marathon is now the qualifying time for the Boston marathon.

Are we suddenly breeding more talent?

No. But training has improved immeasurably.

Practicing effectively

It is not, then, simply practice that is important. It is the right practice. Ericsson & Charness distinguish between deliberate practice – which involves specifically tailored instruction and training, with feedback, and supervision - and the sort of playful repetition more characteristic of people who enjoy an activity and do it a lot. Most people reach an acceptable level of performance, and then are satisfied. The "talented" ... keep on.

References: 
  1. Ericsson, K.A. & Charness, N. Expert performance: Its structure and acquisition. In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp200-255.
  2. Howe, M.J.A., Davidson, J.W. & Sloboda, J.A. 1999. Innate talents: Reality of myth? In S.J. Ceci & Wendy M. Williams (eds) The nature-nurture debate: The essential readings. Essential Readings in Developmental Psychology. Oxford: Blackwell. Pp168-175.

Footnoted references

  1. Ackerman, P.L. 1988. Determinants of individual differences during skill acquisition: cognitive abilities and information processing. Journal of Experimental Psychology: General, 117, 299-318.
  2. Bouchard, T.J., Lykken, D.T., McGue, M., Segal, N.L. & Tellegen, A. 1990. Sources of human psychological differences: the Minnesota Study of Twins Reared Apart. Science, 250, 223-8.
  3. Brady, P.T. 1970. The genesis of absolute pitch. Journal of the Acoustical Society of America, 48, 883-7.
  4. Ceci, S.J., Baker, J.G. & Bronfenbrenner, U. 1988. Prospective remembering, temporal calibration, and context. In M. Gruneberg, P. Morris, & R. Sykes (eds). Practical aspects of memory: Current research and issues. Wiley.
  5. Charness N Clifton J & MacDonald L. 1988. Case study of a musical mono-savant. IN LK Obler & DA Fein (eds) The exceptional brain: Neuropsychology of talent and special abilities (pp277-93). NY: Guilford Press.
  6. Chase, W.G. & Ericsson, K.A. 1981. Skilled memory. In J.R. Anderson (ed). Cognitive skills and their acquisition. Erlbaum.
  7. Coon, H. & Carey, G. 1989. Genetic and environmental determinants of musical ability in twins. Behavior Genetics, 19, 183-93.
  8. Dark, V.J. & Benbow, C.P. 1990. Enhanced problem translation and short-term memory: components of mathematical talent. Journal of Educational Psychology, 82, 420-9.
  9. Dark, V.J. & Benbow, C.P. 1991. The differential enhancement of working memory with mathematical versus verbal precocity. Journal of Educational Psychology, 83, 48-60.
  10. Davis, M. 1994. Folk music psychology. Psychologist, 7, 537.
  11. Ericsson, K.A. 1990. Peak performance and age: an examination of peak performance in sports. In P.B. Baltes & & M.M. Baltes (eds). Successful aging: Perspectives from the Behavioral Sciences. Cambridge University Press.
  12. Ericsson, K.A. & Faivre, I.A. 1988. What's exceptional about exceptional abilities? In K. Obler & D. Fein (eds). The exceptional brain. Guilford Press.
  13. Ericsson, K.A., Tesch-Romer, C. & Krampe, R. Th. 1990. The role of practice and motivation in the acquisition of expert-level performance in real life. In M.J.A. Howe (ed). Encouraging the development of exceptional abilities and talents. British Psychological Society.
  14. Ericsson, K.A., Krampe, R.Th. & Heizmann, S. 1993. Can we create gifted people? In G.R. Bock & K. Ackrill (eds). The origins and development of high ability. CIBA Foundation Symposium, 178. Wiley.
  15. Ericsson, K.A., Krampe, R.Th. & Tesch-Romer, C. 1993. The role of deliberate practice in the acquisition of expert performance. Psychological Review, 100, 363-406.
  16. Feldman, D.H. 1980. Beyond universals in cognitive development. Norwood, NJ: Ablex.
  17. Feldman, D.H. 1986. Nature's gambit: Child prodigies and the development of human potential. NY: Basic Books.
  18. Forbes, C. 1992. The Polgar sisters: Training or genius? NY: Henry Holt.
  19. Fowler, W. 1981. Case studies of cognitive precocity: the role of exogenous and endogenous stimulation in early mental development. Journal of Applied Developmental Psychology, 2, 319-67.
  20. Gustin, W.C. 1985. The development of exceptional research mathematicians. In B.S. Bloom (ed). Developing talent in young people. Ballantine.
  21. Hayes, J.R. 1981. The complete problem solver. Franklin Institute Press.
  22. Howald, H. 1982. Training-induced morphological and functional changes in skeletal muscle. International Journal of Sports Medicine, 3, 1-12.
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Physical activity saves hippocampus in people at risk of Alzheimer's

A study involving 97 healthy older adults (65-89) has found that those with the “Alzheimer’s gene” (APOe4) who didn’t engage in much physical activity showed a decrease in hippocampal volume (3%) over 18 months. Those with the gene who did exercise showed no change in the size of their hippocampus

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11 new genetic susceptibility factors for Alzheimer’s identified

The largest international study ever conducted on Alzheimer's disease (I-GAP) has identified 11 new genetic regions that increase the risk of late-onset Alzheimer’s, plus 13 other genes yet to be validated. Genetic data came from 74,076 patients and controls from 15 countries.

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