SES and IQ: Longitudinal twin study

Yet another study demonstrating the significant relation between SES and intelligence, this time a large longitudinal study of twins. Click on images to enlarge. Prior SES posts can be found here.







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Research Byte: Children's writing ability related to processing speed (Gs), general intelligence and parent education

Double click on images to enlarge. Looks like article worth reading.









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More on SES and brain development

See my prior brief post on new article on brain development and SES
research. The MOUSE TRAP blog provides a more detailed review and
commentary. See URL below.

http://the-mouse-trap.blogspot.com/2009/03/ses-and-developing-brain.html

Kevin McGrew PhD
Educational/School Psych.
IAP (www.iapsych.com)

Sent from KMcGrew iPhone (IQMobile). (If message includes an image-
double click on it to make larger-if hard to see)

SES and brain functions

How does SES related to neurological functioning?

Much has been written and summarized regarding the relation between SES, achievement, and intelligence. More recently on the scene are researchers trying to establish links between SES and neurological functioning. In the recent edition of Trends in Cognitive Sciences (on of my favorite science journals for providing brief overview summaries of topics), Hackman and Farah summarize much of this literature. I found the strongest links between SES and the executive function and language systems of the brain (they organized their review around five primary brain systems) of most interest. The discussion of the operationalization of the construct of SES was also informative and should be reviewed by those doing research on the relations between SES and intelligence and/or those who design representative norm samples for intelligence and achievement tests.

Technorati Tags: psychology, neuropsychology, school psychology, neuroscience, education, educataional psychology, brain structures, SES, IQ, IQ scores, IQ tests

IQ bytes #1: SES, working memory, ECTs

I offten find that although I may not be interested in the specific focus of a published study, a skim of the intro/review of the literature section is often informative. I frequently find nice summaries of concepts, research, definitions, ideas, etc....and I have always wanted to find a way to store them.

I'm now experimenting with a pen scanner (note - I had used one 2-3 years ago but, for some reason had moved away from using it). The new scanner is a much better one than my old model, although produced by the same company (InfoScan). Click here for the model I'm using.

On a recent trip I was skimming the latest issue of Intelligence and I found three interesting bytes of information in the intro section of three different articles. I scanned the information I wanted and it is produced, as is, below. The specific references are provided. Italic emphasis is by me...the blog dictator. Any URL links are also my doing. Enjoy these little bytes. I hope (but can't promise) to do this more often.

On Elementary Cognitive Tasks (ECTs)

Schweizer, K. (2007). Investigating the relationship of working memory tasks and fluid intelligence tests by means of the fixed-links model in considering the impurity problem. Intelligence, 35(6), 591-604.

• One of the oldest ideas in intelligence research is the attempt to describe intelligence in terms of speed of information processing.
• During the past three decades the so-called mental speed approach to human intelligence has provided evidence for a substantial relationship between psychometric intelligence and speed of information processing in elementary cognitive tasks (ECTs) which require minimal cognitive demands on the participant. The rationale of ACTS is that because these tasks are so easy they leave no room for intelligent strategic variations so that differences in performance can only be attributed to differences in the speed with which stimuli are processed and simple decisions are made.
• Typical ECTs include cognitive processes such as encoding or inspection time (e.g., Kranzler & Jensen, 1989), searching for information in short-term memory (Sternberg, 1969), long-term memory retrieval (Posner, Boles, Eichelman, & Taylor, 1969), and simple and choice reaction time (RT) following the rationale of flick (e.g., bensen, 1987; Roth, 1964).

On varying correlations between measures of working memory and general intelligence

Rammsayer, T. H., & Stahl, J. (2007). Identification of sensorimotor components accounting for individual variability in Zahlen-Verbindungs-Test (ZVT) performance. Intelligence, 35(6), 623-630

• The question of whether working memory contributes to intelligence has stimulated a large number of studies. As consequence, many correlational results suggesting the existence of a substantial relationship are available. Ackerman, Beier and Boyle (2005) report a metaanalytic investigation of 57 studies and suggest a correlation of .48. The Inspection of the individual results reveals that this field of research shows a high degree of heterogeneity. There are rather low besides very high correlations. The results obtained by means of structural equation modeling are most impressive. Some studies even suggest near identity of working memory and intelligence with respect to individual differences.
• The heterogeneity of results demands for an explanation. Actually, there is a number of potential explanations. For example, the difference between correlations observed at the manifest level on hand and at the latent level on the other hand provides explanation. Different degrees of similarity between measures for the assessment of working memory on one hand and of intelligence on the other hand give rise to another explanation (Schweizcr, 2005). Samples originating from different populations, which in varying degrees allow age to act as moderator can also be accepted as explanation since age was found to be an influential source (Salthouse, 2005). Furthermore, there is the impurity of measures [Blog dictator comment - often called construct irrelevant variance] as explanation. There may different degrees of impurity. If impurity is given, one part of the observed relationship is due to the intended source of performance whereas the other part is due to another source. Impurity calls the interpretation of the result into question.

On SES (individual and community level variables) and intelligence

Johnson, W., Mcgue, M., & Iacono, W. G. (2007). Socioeconomic status and school grades: Placing their association in broader context in a sample of biological and adoptive families. Intelligence, 35(6), 526-541.

• Over 20 years ago, White (1982) published a meta-analysis documenting the fact that, measured at the level the individual, the correlation between socioeconomic tabus (SES) and academic achievement is rather modest, averaging about .22. At the same time, when measured at the level of some aggregated unit of analysis such as the schoo1 or the neighborhood, the correlation is much higher, ranging as high as .80. Though SES is a variable that applies to the individual or family, its much higher aggregate than single-family correlation with academic achievement implies that people of similar SES tend to cluster together. To the extent this is true, children receive similar SES influences from both their families and their surrounding communities. If the community influences are strong, SES has the potential to be a powerful environmental variable exerting broad-based effects at a population level, despite its relatively modest effects at the level of the individual. It is probably for treason that SES continues to be so interesting to researchers investigating educational outcomes.
• [Blog dictator comment - see prior post where I highlighted a more current SES meta-analytic summary that updates the classic White (1982) review. As mentioned in that note, community SES is a very important variable when it comes to designing sample specifications for the standardization of cognitive tests --- but it is often overlooked.
  

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, intelligence, IQ, IQ tests, SES, cognition, ECTs, working memory, g, general intelligence, Gsm, community

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IQ and wealth: The dumb rich and the smart poor

The following is a guest blog post by Joel Schneider (Clinical psychologist, Illinois State University), a member of IQs Corner Virtual Community of Scholars project.

The Dumb Rich and the Smart Poor

or

I Am as Tall as the Rocky Mountains!

(After controlling for barometric pressure)

• Zagorsky, J. L. (in press). Do you have to be smart to be rich? The impact of IQ on wealth, income and financial distress. To appear in Intelligence. (click here to view)

Abstract

How important is intelligence to financial success? Using the NLSY79, which tracks a large group of young U.S. baby boomers, this research shows that each point increase in IQ test scores raises income by between $234 and $616 per year after holding a variety of factors constant. Regression results suggest no statistically distinguishable relationship between IQ scores and wealth. Financial distress, such as problems paying bills, going bankrupt or reaching credit card limits, is related to IQ scores not linearly but instead in a quadratic relationship. This means higher IQ scores sometimes increase the probability of being in financial difficulty.

Comments

If you’ve ever been around very wealthy people, you might have noticed that they generally feel that it is in poor taste to be too concerned about money. Poor people, on the other hand, don’t have the luxury of not focusing on the importance of money. In much the same way as wealthy people think about money, smart people such as bloggers, journalists, and their typical readers generally find it distasteful to believe in the importance of intelligence and often delight in research that shows that IQ tests are irrelevant.

Now we have a study that can make both smart and rich people feel good. News reports of this article by Jay Zagorsky claim that IQ doesn’t matter when it comes to amassing wealth. Smart rich people can react to the article by thinking, “Yes, of course. It is not that I have special gifts for which I cannot take credit. No, I am rich because I earned it. Anyone can do the same. Poor people could be rich if they would only do what I did. It must be that I am a morally superior person.” People without a lot of money might be tempted to conclude, “This explains why there are so many rich idiots.” Viewed the right way, there is something in this study for everyone.

Unfortunately, the news reports about this study have oversimplified the study to the point of gross misinterpretation. The journalists cannot be blamed for the oversimplification, however. Indeed, the abstract of the article has the (entirely correct but confusing) words, “Regression results suggest no statistically distinguishable relationship between IQ scores and wealth.”

But what does this mean? It certainly sounds like IQ and wealth have no causal connection. However, as the title of this post suggests, regression results can be horribly misleading when we address issues of causality. People who remember the adage “correlation does not imply causation” might not happen to know that regression analysis is like correlation on steroids. At its core, regression is essentially the same thing as correlation and therefore it has the same weaknesses as correlation when it comes to helping us know what causes what.

Just because I can use regression to show that the houses in my neighborhood are just as tall as the Rocky Mountains after statistically controlling for barometric pressure at the summits of each house and mountain does not mean that I have proved that there is no true difference in the heights of houses and mountains. It also doesn’t prove that houses and mountains would be the same height if we were to equalize the barometric pressure differences. We know that such an analysis is stupid because we know that changing altitude causes air pressure to change and that changing air pressure has no effect on altitude.

So what exactly does the study say? First, it distinguishes between income and wealth (net worth). It is possible to amass a fortune by being frugal with a small income and it is possible to spend oneself into bankruptcy even with a high income. The article confirms that the relationship between IQ and income is, although rather modest (r = .297), statistically robust. Squaring the correlation suggests that IQ explains “only” 9% of the variance in income. This leaves 91% of the variance in personal income to be explained by other factors. The correlation of IQ and wealth is only half as large (r = .156) and accounts for a mere 2.4% of the variance in wealth. This means that a person’s net worth is determined largely by things other than IQ.

So now we can stick out our tongues, put our thumbs in our ears, wiggle our fingers, and sing, “NAH, nah, nuh, NAH, nuh!” to all our smarty-pants rivals in high school who thought they were SO smart. IQ is so insignificant. It explains only 2.4% of the variance in wealth!

…But wait, what does this look like graphically? Taking the data from Table 2 of the Jagorsky article and plotting the relationships of IQ with net worth on the left axis and income on right axis, you get a graph like the one at the top of this blog post (see above)

Yes, the low correlation between IQ and wealth does, in fact, mean that low IQ does not doom a person to poverty and that high IQ does not guarantee wealth. However, the difference between the median net worth of the lowest IQ category ($5,775) and that of the highest ($133,250) is hardly trivial. To make an analogy, your basketball skills wouldn’t be that much better if you grew an extra inch. However, to claim that height is irrelevant in basketball is utter nonsense.

The Jagorsky article is not claiming that there is no relationship between wealth and IQ. It does, however, claim that this relationship disappears after controlling for a number of sensibly selected variables such as age, marital status, education, race, inherited wealth, and so forth. If these variables were uncorrelated with IQ, the interpretation of this finding would be straightforward. Unfortunately, many of these variables are robustly correlated with IQ and this makes the interpretation of the findings rather difficult.

Now, not even the most naïve and enthusiastic “IQ Believer” would argue that IQ has an unmediated relationship with wealth. That is, no one believes that wealth is a direct consequence of IQ (“The test results are in and you scored quite high. Here is your check!”). IQ, if it has a causal connection with wealth at all, must act through one or more other variables. For example, high IQ may give some people a distinct advantage in acquiring more education. Many high paying jobs (e.g., jobs in the fields of law and medicine) use educational degrees as credentialing mechanisms. Thus, in this case, the proximal cause of higher income is the acquisition of educational credentials but IQ would still be an important distal cause.

Thus, when Jagorsky writes that the relationship between IQ and wealth disappears after controlling for a particular set of variables, it is essentially a claim to have identified which variables are likely to mediate the effect of IQ on wealth. What is unresolved is whether IQ really is a cause of variables such as educational attainment or simply a meaningless byproduct of education. Unfortunately, regression analyses alone cannot distinguish between the 2 causal models visually represented by a path diagram figure (click here). For that, we need other sources of information.

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, intelligence, IQ, IQ test, IQ score, wealth, income, financial stress

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Parenting, race, SES and cognitive development

[double click on image to make larger]

It is no secret that I'm a firm believer that researchers, practitioners, and policy-makers need to pay closer attention to large-scale, national, longitudinal studies that use multiple indicators and complex statistical model testing to understand important child development issues. One such study, which is now producing some high quality and interesting research articles (and which I previously blogged about re: impact of school retention policies) is the Early Childhood Longitudinal Study.

Although not the easiest read, I found the conceptual model (see figure above) and literature review in the following article of interest. I love conceptual models that provide a means by which to organize data, research, etc. that pass through my mind.

• Raver, C. C., Gershoff, E. T., & Aber, J. L. (2007). Testing equivalence of mediating models of income, parenting, and school readiness for white, black, and hispanic children in a national sample. Child Development, 78(1), 96115. (click here to view)

Random tidbits from the mind and brain blogpshere 10-31-06

• Interesting article at BPS Research Digest on boosting Gv (visual skills) in lower SES populatons to boost their confidence in the world of work, and increase job performance.
• A tech tidbit from the Download Squad. I'm always looking for ways to become a paper-less worker. Today they have highlighted a new light-weight e-book reader from Adobe. One of these days I'm going to try doing some e-book reading on a regular basis.
• The Eide Neurolearning blog has posted a supposed fMRI showing the impact of chocholate on the brain...just in time for Halloween.
  

Technorati Tags: psychology, educational psychology, neuropsychology, cognition, cognitive, intelligence, IQ, Gv, visual-spatial, visual processing, e-book reader, Adobe, Halloween, mind, brain

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Low IQ (intelligence) = earlier death in poor countries?

Interesting (and likely controversial) post at the British Psychologcial Study re: a researcher who suggests that low IQ (intelligence) may be related to shorter life expectancy in poor countries. Links to other related studies are also included.


Technorati Tags: psychology, educational psychology, school psychology, developmental psychology, death, life expectancy, poverty, poor countries, cognition, cognitive, SES, IQ, IQ tests, IQ scores, intelligence

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Today's random tidbuts from the mind and brain blogsphere

A random tidbits from today's mind and brain blogsphere:

• BPS Research Digest - drug may enhance intuition (link)
• CogNews - discovery of gene that may help explain evolution of human brain capacity (link)
• Developing Intelligence - good discussion and links to article related to important aspect of executive functioning - disinhibition (link)
• Mind Hacks - summary of research (reported in Neurocritic) on neuroscience of poverty and mind/brain development (link)
  

Technorati Tags: psychology, educational psychology, school psychology, educadtion, cognition, intelligence, intuition, brain development, IQ, executive function, poverty, neuroscience, neurology, neuropsychology, mind

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More on SES and IQ/achievement: SES and phonemic awareness interaction

The following is a post by the blogmaster (Kevin McGrew), who is also a member of IQs Corner Virtual Community of Scholars project.

More on the relationship of SES and cognitive/academic achievement.

The abstract and conclusions for the article below speak for themsevles. Prior related blog posts include genetic/environement/SES interactions and the relations (based on a top-notch meta-analysis study) between SES and academic achievement.

• Noble, K. , Farah, M. & McCandiss (2006). Socioeconomic background modulates cognition–achievement relationships in reading. Cognitive Development, 21 349–368 (click here to view article)
  

Abstract

• Multiple factors contribute to individual differences in reading ability. The two most thoroughly examined are socioeconomic status (SES) and phonological awareness (PA). Although these factors are often investigated individually, they are rarely considered together. Here we propose that SES systematically influences the relationship between PA and reading ability, and test this prediction in 150 first-graders of varying SES and PA. Results confirm a multiplicative relationship between SES and PA in decoding skills, such that decreased access to resources may amplify cognitive risk factors for poor decoding, whereas greater access to resources may buffer reading skills among children with weaker PA. Attempts to identify the cognitive and experiential factors driving development must acknowledge the complex, synergizing relations between these factors.

Conclusions

• SES has a systematic effect on reading skills, after controlling for PA. However, the nature of this effect changes, depending on both the reading measure and the PA range examined. SES disparities in decoding are greatest at lower PA levels, whereas SES disparities in single word reading and passage comprehension are consistent across all PA levels. Interventions for poor readers must therefore target both the development of phonological skill and the elimination of key discrepancies in environmental advantage. Attempts to identify the cognitive and experiential factors driving development must likewise acknowledge the potentially complex, synergizing relations between these factors.
  

Technorati Tags: psychology, education, educational psychology, achievement, cognition, IQ, intelligence, SES, phonemic awareness, phonological awareness, Ga, PC

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