Genetics: The Heritability of Intellectual Ability David Kerr

Nature vs Nurture

What is heritability? Heritability looks at what variance of a trait throughout the population is due to genetic factors (I.E. nature) Other factors that impact the prevalence of traits are characterized as environmental factors (I.E. nurture) Some traits have high heritability, whereas others are highly impacted by the environment https://i2.wp.com/scienceblogs.com/gregladen/files/2014/03/tumblr_m21zyrem9k1rt8lhlo1_400.jpg?fit=400%2C269

Why test intelligence and not physical ability? http://cdn.images.express.co.uk/img/dynamic/1/590x/mo-farah-417977.jpg Intelligence is less conditional on physical dimensions Even playing field makes it easier to study differences Standardized tests are in place for measuring and testing intelligence 5’9” 128lbs 6’5” 305 lbs https://3.bp.blogspot.com/-7gxOrUJCq6Q/V7OMFvpKjfI/AAAAAAAAOfg/bf4VWM2AV_4ERAM39sSOIKR1e_tcTTf5wCEw/s1600/Michael-Phelps-towers-over-Simone-Biles01.jpg http://www2.pictures.zimbio.com/gi/IAAF+Compeed+Golden+Gala+Rome+du496OyAStHl.jpg

From: The Cambridge Handbook of Expertise and Expert Performance The Influence of Experience and Deliberate Practice on the Development of Superior Expert Performance From: The Cambridge Handbook of Expertise and Expert Performance (K Anders Ericsson, 2006)

Ericsson on Practice Practice is necessary and what takes everyday performance to expert performance Claiming that intellect is heritable does not challenge this Merely suggests that some people are more predisposed to be able to achieve these expert levels of performance K Anders Ericsson, 2006 P. 691 K Anders Ericsson, 2006 P. 687

Nature, Nurture, and Cognitive Development from 1 to 16 years: A Parent-Offspring Adoption Study (Plomin et al., 1997)

Parent-offspring study model Twenty year longitudinal study Colorado Adoption Project Institute of Behavioural Genetics University of Colorado Boulder Large sample size 490 total subjects Multiple testing times Matched pair control group http://www.colorado.edu/brand/sites/default/files/logos-w-names.png

Parent-Offspring Study Findings IQ heritability increased with age In infancy and early childhood children mirrored their adoptive parents By age 14 correlation between Adoptive Parent IQ and child IQ was at zero Plomin et al., 1997 P. 444

Results in Specific Cognitive Abilities Top Left: Verbal Ability Top Right: Spatial Ability Bottom Left: Speed of Processing Bottom Right: Recognition memory Plomin et al., 1997 P. 445 (Plomin et al., 1997) P. 445

Application of Hierarchical Genetic Models to Raven and WAIS Subtests: A Dutch Twin Study (Rijsdijk, Vernon & Boomsma, 2002)

Dutch Twin Study Model Longitudinal Study Large sample size 194 Pairs of twins Multiple testing times Multiple Completed tests Including tests for reaction time and nerve conductivity

Dutch Twin Study Results High heritability in Verbal skills (VOC, VC & VIQ) Performance IQ and Full Scale IQ Similar tests to those completed in the Parent-offSpring Study Claim that there is little impact from environment Rijsdijk, Vernon & Boomsma, 2002 P. 205

Future Research: What now?

Future Research Heritability of intellect and it’s impact on learning “Hard work beats talent, when hard work doesn’t practice” Test to see at what point the heritability advantage ceases to exist and those who are better practiced begin to exceed the natural abilities that the others have Areas to test for heritability advantage Spatial problem solving (mazes puzzles, tetris style spatial situations, Rubix Cube) Memory (long and short term; audible, visual and factual) Fine motor coordination activities (mirror tracing, reaction times) These areas were selected because they are intellect-based problems that are solved in a physical space, as well as the fact that there can be strategies learned to aid in their completion, allowing for the acquisition of skill

References Deary, I., Spinath, F., & Bates, T. (2006). Genetics of intelligence. European Journal of Human Genetics : EJHG, 14(6), 690-700. doi:10.1038/sj.ejhg.5201588 Ericsson, K. A. (2006). The influence of experience and deliberate practice on the development of superior expert performance. In K. A. Ericsson, N. Chamess, P. J. Feltovich & R. R. Hoffman (Eds.), The Cambridge handbook of expertise and expert performance (1st ed., pp. 685--706). Cambridge, UK: Cambridge University Press. Plomin, R., Fulker, D. W., Corley, R., & DeFries, J. C. (1997). Nature, nurture, and cognitive development from 1 to 16 years: A parent offspring study. Psychol.Sci., 8(6), 442--447. Polderman, T. J. C., Gosso, M. F., Posthuma, D., Van Beijsterveldt, Toos C E M, Heutink, P., Verhulst, F., & Boomsma, D. (2006). A longitudinal twin study on IQ, executive functioning, and attention problems during childhood and early adolescence. Acta Neurologica Belgica, 106(4), 191-207. Rijsdijk, F., Vernon, P. A., & Boomsma, D. (2002). Application of hierarchical genetic models to raven and WAIS subtests: A dutch twin study. Behavior Genetics, 32(3), 199-210. doi:10.1023/A:1016021128949