Although we believe intelligence to be a heritiable trait (in that the genetic contribution of one's parents might bestow on a child part of their intellectual potential), there is undoubtably an influence of the environment and early socialisation experiences that are influenced by cultural beliefs and educational experiences. These experiences are partly shaped by the contribution of caregivers, family and teachers as a child progresses through the educational system. And there have certainly been changes in those educational environments rom the local, state, and national level education systems of most nations. It might seem reasonable, therefore, that we might see rises in the level of reading literacy, and with the cheap and ubiquitous nature of technology in our modern culture we might also see rises in numerical and scientific literacy as well. But not necessarily intelligence, as defined by psychometric IQ.
So it seems surprising, therefore, to conider that IQ scores are rising. This phenomenom, known as the 'Flynn effect' after the researcher James Flynn who made the discovery, is robust and has been observed for both developed and developing nations. It amounts to a gain on average of about three IQ points per decades. It is for this reason that tests of psychometric intelligence such as the WAIS for adults and WISC for children must be periodically refined and updated so as to prove a reliable and valid discriminator of individual ability. This process, referred to as norming, involves recruiting large demographically representative samples of the general population so that an individual's performance can be measured relative to the population from which he or she is drawn. Test norms can quickly become outdate, which places an onus on those who administrate psychological to use the most recent version of the test available to produce an evalation of an individual that is meaningful and valid.
There are various reasons mooted for the global rise in IQ scores from better nutrition and medical care, better access to schools and to learning, etc. A full discussion of the debate is beyond the scope of this blogpost, but it rasies some interesting and thoughtprovoking implications. Are we all, as a planet, growing smarter across the generations at a uniform rate or are some of us advancing at a faster rate?
In his latest book, James R. Flynn (2012) evaluates this proposition and comes to some startling conclusions. His ata suggest that women may be gaining on men at a faster rate over the decades. If so, the implication would be that gender gaps in cognitive abilities will shrink over time and that many of the claims of sex differences in the literature may not hold true in the future. We live in interesting times.
References
Flynn, J. R. (2012). Are we getting smarter? : Rising IQ in the twenty-first century. Cambridge; New York: Cambridge University Press.
