Friday, December 21, 2007

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.
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