Tuesday, May 30, 2006

Gf an g--distinguishable or indistinguishable ? -- Guest post by John Garruto

The following is a guest post by John Garruto, school psychologist with the Oswego School District and member of the IQs Corner Virtual Community of Scholars. John reviewed the following article and has provided his comments below.
  • “Any intelligence test worth its salt has a matrices task on it.”-George McCloskey-NASP Toronto-2003.
Blair, C. (2006). How similar are fluid cognition and general intelligence? A developmental neuroscience perspective on fluid cognition as anaspect of human cognitive ability. Behavioral and Brain Sciences, 29, 109-160. (Click here to view article).

  • This target article considers the relation of fluid cognitive functioning to general intelligence. A neurobiological model differentiating working memory/executive function cognitive processes of the prefrontal cortex from aspects of psychometrically defined general intelligence is presented. Work examining the rise in mean intelligence-test performance between normative cohorts, the neuropsychology and neuroscience of cognitive function in typically and atypically developing human populations, and stress, brain development, and corticolimbic connectivity in human and nonhuman animal models is reviewed and found to provide evidence of mechanisms through which early experience affects the development of an aspect of cognition closely related to, but distinct from, general intelligence. Particular emphasis is placed on the role of emotion in fluid cognition and on research indicating fluid cognitive deficits associated with early hippocampal pathology and with dysregulation of the hypothalamic-pituitary-adrenal axis stress-response system. Findings are seen to be consistent with the idea of an independent fluid cognitive construct and to assist with the interpretation of findings from the study of early compensatory education for children facing psychosocial adversity and from behavior genetic research on intelligence. It is concluded that ongoing development of neurobiologically grounded measures of fluid cognitive skills appropriate for young children will play a key role in understanding early mental development and the adaptive success to which it is related, particularly for young children facing social and economic disadvantage. Specifically, in the evaluation of the efficacy of compensatory education efforts such as Head Start and the readiness for school of children from diverse backgrounds, it is important to distinguish fluid cognition from psychometrically defined general intelligence.

John Garruto's comments (with only minor edits by the blogmaster)

  • To begin with, this article was very lenghty and was difficult to summarize ala blog format. Half of it is a theoretical and literary review while the other half is peer commentary (which to be honest-I haven’t read it yet because I wanted to write my own thoughts and not be influenced by others.) So-I might write on the peer commentary later-or not. [Note to readers - all commentaries are included with the target article at the article link above.]
  • The purpose of this article is to separate ‘g’ (or overall general intellectual functioning) from ‘Gf’ (or fluid reasoning.) Blair begins by talking about what fluid reasoning is and ways that it can be measured (he usually cites Raven’s Progressive Matrices as a dependent measure of fluid reasoning). Overall he uses psychometric evidence of Gf (in terms of its relation to ‘g’ with research by Gustaffson), neuroscientific (in terms of results of MRI, PET, and fMRI studies showing activation or underactiviation of areas that relate to Gf output) and also psychiatric/developmental disorder problems (differentiating Gf skills of students with ADHD, CD, autistic, schizophrenic, PKU, and LD.)
  • In terms of dissociating ‘g’ from ‘Gf’, Blair highlighted different approaches. In one, he talked about how in the “standard” of IQ testing (the Wechsler), Gf is not even measured, yet ‘g’ is measured.
  • Fascinatingly, Blair focuses on neuropsychological issues that are related to Gf output. He talks about the corticolimbic circuit, which involves the interaction of the hippocampus, the amygdaloid structure, the anterior cingulate cortex, and the prefrontal cortex (PFC). As I understood the article, with the greater emotional roles played by some of these brain structures, excitation of emotion can inhibit the role of the PFC--having an adverse reaction on Gf. He further discusses the ramifications of adverse environmental experiences on the roles of Gf--specifically mentioning that a child being reared in a stressfull environment might present themseleves with inhibited Gf functioning. In terms of intervention, he mentions the role of Gf being explicitly taught..a position that merits additional research.
  • Much of this article was exciting to read. Admittingly, I'm only an advanced beginner in neuropsychology knowledge, but the article highlighted some important tenets. First, much of our functioning is related to the interdependence of various skills. Educators (and psychologists) seem to be drawn to the notion that deficits are localized in nature--but no matter what we’re looking at (e.g., interactions of neuropsychological processes, cognitive processes, or whatever) can have a multiplicative impact. We need to remember our basic statistics and be mindful that interactions can be substantial. Another important insight for me was the relationship of executive functioning to fluid intelligence. In the past I’ve always viewed EF as way by which we can be more efficient with our thinking--taking control and manipulating our processes. However, when I look at measures of EF (for example, card sorting tasks, or Concept Formation on the WJ-III--which taps both Gf and EF), the idea that Gf is related to EF (being explicitly stated in the article) has led me to think this is something I need to think about differently.
  • Much of this article was educational for me, but I nevertheless, I do have a few criticisms. First, although the article has a 2006 publication date (even give a few years for editorial review), the article focused primarily on older tests (including the old Wechsler and WJ-R and SB-IV)...most of which had revisions that I would imagine were available at the time the article was written. For example, the WISC-IV now includes measurement of Gf. In fact, it was George McCloskey (who gave a talk on executive processes in 2003 NASP workshop) where he said that any intelligence test that is worth its salt has a matrices task on it (hence the quote at the top of this blog post). Clearly the importance of Gf is being mentioned in many circles. Blair also talked about extracting the variance of Gf from ‘g’. I recall someone stating (on the NASP listserv) that “You can't remove the general ability variance from the test, and then look at what is left from the factors. The same variance that is in the factors is the same variance that is in the global ability score. These data are collinear." Now my knowledge of statistics also pales to this listserv poster, but it seemed to be an endorsement of something that shouldn’t be done. Also of importance, Blair extols the virtues of cross-battery assessment (and should be applauded for doing so) as a way to secure Gf measures above and beyond giving the WISC. As noted before, we’re well beyond that--contemporary CHC theory puts Gf in its own factor and many tests are measuring it (and some have measured it for years-such as the Differential Ability Scales in 1990!). Cross battery assessment is one way to do it. One could administer the WJ-III and get a Gf factor by giving two subtests. Furthermore, there is little talked about in terms of narrow abilities subsumed by Gf--which are very different from each other.
  • Blair spends much of his time supporting the notion of differentiating Gf from g. Such an approach seems worthwhile (actually most research that de-emphasizes ‘g’ outside of a mental retardation diagnosis gets high marks from me.) However, I remember being at a recent testing "best practice" conference where I had asked the speakers about their thoughts regarding the diagnosese of mental retardation if one or two subtests were in the below average to average range (some maintain that is evidence that there is no MR--but when you’re giving a lot of subtests--regression to the mean can be inevitable.) One of the speakers (John Willis) replied that he would be highly skeptical of an MR diagnosis if one of the factors that was in the low average range measured fluid reasoning.
  • Despite the above criticisms, the focus on the neuropsychological processes associated with fluid reasoning, as well as the notion of relating Gf to executive functions, are important. More important is that Gf has been thought to be relatively immune from cultural experiences...however; if the hypotheses of this article prove to be valid--then early environmental emotional stressors might have a negative impact on Gf--marking a significant contrast to the widely held belief that Gf is somewhat immune from these experiences. I believe this is an important article for school psychologists, learning disabilities specialists, specialists in intellectual functioning, and cognitive scientists to read. There were many points in this article that, due to space, I was not even able to touch upon.

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