Wednesday, December 27, 2006

Random tidbits from mind blogsphere 12-27-06

  • Thanks to Boing Boing for the interesting post regarding "knitting and mathematics."
  • The brain fitness movement (with regard to late adulthood) made a splash on the New York Times today.
  • More on Go (olfactory) abilities over on the Gene Expression blog. Check out prior Go posts I've made.
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Tuesday, December 26, 2006

Spatial question...need responses

Someone just posted a link to the following as a comment to one of my posts and asked for feedback. I decided to post it to all readers. Readers...please provide feedback via the comment function.

Friday, December 22, 2006

Age decline in reasoning - speed and executive abilities

[Double click on table to enlarge for easier viewing]

What may be the reasons for decreased fluid intelligence (Gf) with increasing age?

According to recent study (see reference and abstract below),two of the primary causative factors for decreased fluid intelligence (as established by recent research) are (a) decreased speed of cognitive processing (a generalized cognitive slowing mechanism) and (b) decreases in the executive functions of the frontal lobes as evidenced by decreased frontal lobe volume, alterations in frontal lobel cell morphology, and reductions in cerebral blood flow to the frontal and prefrontal brain lobes. The current study investigated the relative contributions of processing speed and frontal lobe function on decreases in Gf. The abstract for the article (together with URL link) is reproduced below. I will summarize some of the major findings plus add my two cents.

I have 2 cents worth of methodological comments. First, measures of reaction time (Gt) operationally defined cognitive processing speed in this study. According to the CHC taxonomy, these measures represent aspects of the broad domain of Gt (broad reaction time), which is NOT to be confused with broad cognitive processing speed (Gs). Thus, the current results are specific to the influence of Gt and may not be generalizable to Gs abilities. Additional research with valid Gs markers is needed.

Second, the authors continue the unfortunate tradition of using the Wechsler Block Design test as a marker for Gf. Contemporary Gf-Gc/CHC joint exploratory and confirmatory factor studies have convincly indicated that Block Design is a strong measure of visual-spatial processing (Gv)...not Gf. Luckily, the authors also use the Wechsler Matrix Reasoning test which is a valid indicator of Gf. Given the problems with Block Design, I recommend that readers of this article only pay attention to the results focused on understanding the decline in the Matrix Reasoning test (Of course, the Block Design findings can be interpreted in the context of Gv if that is what is of interest.)

Given this caveat, below are the major conclusions regarding possible explanations for age-related declines in Gf. I believe readers should only focus on the composite Gt measure as the indicator of general reaction time (Gt) and only the analyses that included the Gt, frontal function measures, and age in the analysis (as these provide the most valid and comprehensive explanations from the current study). These findings have been highlighted in red in the above table picture.
  • Frontal (executive) function and Gt, collectively, account for approximately 27 % of the decrease in Gf with age. Chronological age explains and additional 15-16 % of the decline in Gf, above and beyond frontal function and Gt abilities.
  • As noted by the authors, a generalized slowing of cognitive speed contributes to decreased Gf abilities...but, speed is not the entire picture. Decreased frontal functions, as well as other unaccounted for variables realated to age, also contribute to decreased Gf with age. Decreased frontal functions and Gt both contribute uniquely to age-related declines in Gf abilities.
  • Declines in cognitive abilities, in this case Gf, are multiply determined. No one single mechanism can explain age-related changes in cognitive ability.
  • Bottom line - age-related decreases in the ability to reason inductively/deductively and solve novel problems (Gf - fluid intelligence) appear due, in part, to age-related decreased speed of cognitive thinking and decreases in ability to think and manage (executive function) one's own thinking processes ("thinking about thinking"), plus additional factors not clearly delineated.
Bugg, J., Zook, N., DeLosh, E., Davalos, D. & Hasker, D, (2006). Age differences in fluid intelligence: Contributions of general slowing and frontal decline. Brain and Cognition, 62, 9–16 (click here to view)

  • The current study examined the contributions of general slowing and frontal decline to age differences in fluid intelligence. Participants aged 20–89 years completed Block Design, Matrix Reasoning, simple reaction time, choice reaction time, Wisconsin Card Sorting, and Tower of London tasks. Age-related declines in fluid intelligence, speed of processing, and frontal function were observed. Hierarchical regression analyses showed that the processing speed and frontal function measures accounted for significant variance in fluid intelligence performance, but there was also a residual effect of age after controlling for each variable individually as well as both variables. An additional analysis showed that the variance in fluid intelligence that was attributable to processing speed was not fully shared with the variance attributable to frontal function. These findings suggest that the age-related decline in fluid intelligence is due to general slowing and frontal decline, as well as other unidentified factors.
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IQs Corner Headlines from mind blogsphere 12-22-06

All the news thats fit for IQs Corner readers:

This is the 14th installment of IQs Corner Headlines from the Brain and Mind Blogsphere

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Thursday, December 21, 2006

Reading and language development - nice overview

I'm always searching for easy to read overview articles to help myself, and hopefully others, see the forest from the trees regarding complex aspects of human behavior. Today I ran across a 1999 article written for speech and language pathologists which I thought did a very nice job of providing the general gestalt of the process of learning to read and the important relations between early reading/literacy skills and early language development. I particularly like the simplified step-by-step explanation of the basics of learning to read on pages 50-51 (the section titled "Skilled Reading: The Goal")

The reference and abstract for this article (as well as a link to the complete article) are provided below.

Snow, C. E., Scarborough, H. S., & Burns, M. S. (1999). What speech-language pathologists need to know about early reading. Topics in Language Disorders, 20(1), 48-58. (click here to view)

  • The National Research Council report, Preventing Reading Difficulties in Young Children, reviews research on early reading and recommends prevention strategies and optimal interventions for reading difficulties. Since speech-language pathologists often treat children whose language problems co-occur with reading difficulties, they can help inform parents and teachers about the relation between language and literacy difficulties, and help coordinate interventions across these two areas. We summarize the NRC’s conclusions concerning normal reading development and key developmental milestones in the various domains relevant to reading success (phonological awareness, letter identification, the alphabetic principle, automatic word recognition, comprehension strategies).
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Wednesday, December 20, 2006

Random tidbits from the mind blogsphere 12-20-06

  • Thanks to the Brain Blog for a research FYI regarding a recent study on how baseline cognitive functioning relates to rate of decline in basic care of individuals with Alzheimer's disease.
  • Positive Technology Journal has an interesting FYI post re: the increase in mobile social networking (e.g., MySpace and Facebook)
  • Check out Sharp Brains for FYI post regarding new study on benefits of brain fitness exercises.

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Excercise and executive functioning - good for young adults also

Science Daily summarizes a recent study that suggests that exercise, which the extant research has linked to improved neurological/brain function in older adults, may also help younger adults, in this case with regard to executive functioning. Below is the full abstract as well as a link to the complete article.

Abstract (click here for more)
  • Previous reports have indicated a small, positive relationship between physical activity and cognition. However, the majority of research has focused on older adults, with few studies examining this relationship during earlier periods of the life span. This study examined the relationship of physical activity to cognition in a cross section of 241 community dwelling individuals 1571 years of age with a task requiring variable amounts of executive control. Data were analyzed with multiple regression, which controlled for age, sex, and IQ. Participants reported their physical activity behavior and were tested for reaction time (RT) and response accuracy on congruent and incongruent conditions of a flanker task, which manipulates interference control. After controlling for confounding variables, an age related slowing of RT was observed during both congruent and incongruent flanker conditions. However, physical activity was associated with faster RT during these conditions, regardless of age. Response accuracy findings indicated that increased physical activity was associated with better performance only during the incongruent condition for the older cohort. Findings suggest that physical activity may be beneficial to both general and selective aspects of cognition, particularly among older adults.
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How to develop our brightest minds

Nice story in Science Daily regarding the ongoing research by a team of researchers at Vanderbilt (who have been analyzing 35 years of research from the Study of Mathematically Precious Youth) re: the factors involved in developing our talent pool of gifted/bright minds in the sciences.

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Is the Flynn Effect dead? From the mouth of Flynn

A news report in the UK Times is based on an interview with James "Flynn Effect" Flynn. Long story short...Flynn is arguing that the Flynn Effect may be dead...that is.....IQ scores may have stopped increasing.

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Book review. Jensen's Clocking the Mind

The first available review that I've seen of Arthur Jensen's recent book, Clocking the Mind, has just been posted at the Developing Intelligence blog. Take a peak. I do know that formal journal published reviews of this work are in the works (click here).

Tech tidbit - USB storage gift for XMAS

From Boing Boing. Just in time for the holidays. For you tech guys who want to impress your girlfriend....diamond-encrusted USB drives. Be prepared for the sticker shock.

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Sunday, December 17, 2006

IAP listserv n=900+

I'm pleased to announce that the IAP-CHC listerv has recently surpassed the n=900+ membership threshold. Only approximately 100 more members and we shall reach a critical mass of n=1000. If you are a routine reader of IQs Corner Blog, you might want to join the CHC listserv in order to monitor/participate in ongoing CHC and intellectual assessment chatter.

Visit the link above to learn more about the CHC listerv. Below is a brief description.

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Thursday, December 14, 2006

Wednesday, December 13, 2006

IQ, skew and reaction time measurs of general intelligence

A thought provoking Developing Intelligence post (stimulated by Chris Chatham, the DI blogmaster, reading of Jensen's "Clocking the Mind" regarding "IQ & Skew, or why not to log-transform RTs (reaction times)."

Primarily for those interested in the statistical handling of cognitive reaction time measures.

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Bracken Basic Concepts Scale

Bruce Bracken, author of a number of psychoeducational assessment instruments, provided a nice description of one of his instruments (The Bracken Basic Concept Scale) on the NASP listserv today (12-13-06).

I recall being an early fan of the BBCS in my later years as a practicing school psychologist. I thought the BBCS was a much more comprehensive and technically sound measures than the then "top dog" measure of children's basic concepts (The Boehm). In addition, as Bruce mentions in his post, it had the additional feature of being linked to an intervention program.

Bruce was responding to a NASP thread regarding the "utility of cognitive testing." I've decided to reproduce his post below. It is followed by the list of references I have in my private IAP electronic reference database.

Bruce Bracken wrote, on the NASP listserv on 12-13-06 (NOTE - blogmaster snipped one phrase):
  • An author's view - - part of the problem in considering the value of assessment is the dichotomizing of positions as right/wrong, good/bad, valid/invalid, and so on to promote a singular way of thinking. Assessment doesn't have to be dichotomized in such a manner. Before CBM, CBA, or RTI was bandied about, the Bracken Basic Concept Scale (1984) was published as a test designed to assess approximately 300 functional, teachable, relevant language concepts in a norm-referenced or criterion-referenced manner. In 1986 the Bracken Concept Development Program was published, which promoted the application of a test-teach-test model and a direct curriculum/assessment linkage (forerunner to CBM/CBA). The BBCS has been twice revised since the original edition and its multi-level functional assessment/intervention approach is equally relevant with an RTI model. BBCS content has been compared to the early childhood educational standards in all 50 states, and it exceeds the standards in every state (you may download the standards comparisons by copying and pasting the following URL: There are highly reliable, highly valid, educationally relevant, developmentally appropriate, functional norm-referenced tests available to school psychologists, but some critics choose the weakest examples to make their points rather than acknowledge meaningful advances being made in psychoeducational assessment.

Bracken, B. A., Kuehn-Howell, K., & Crain, R. M. (1993). Prediction of Caucasian and African-American preschool children's fluid and crystallized intelligence: Contributions of maternal characteristics and home environment. Journal of Clinical Child Psychology, 22 (4), 455-464.

Laughlin, T. (1995). The school readiness composite of the Bracken Basic Concept Scale as an intellectual screening instrument. Journal of Psychoducational Assessment, 13, 294-302.

Braden, J. P., Gottling, S. H., & Naglieri, J. A. (1993). Confirmatory factor analysis of the planning, attention, simultaneous, successive (PASS) cognitive processing model for a kindergarten sample. Journal of Psychoeducational Assessment, 11, 259-269.

Mclntosh, D. E., Wayland, S. J., Gridley, B., & Barnes, L. L. B. (1995). The relationship between the Bracken Basic Concept Scale and the Differential Ability Scales with a preschool sample. Journal of Psychoeducational Assessment, 13, 39-48.

McIntosh, D. E., Brown, M. L., & Ross, S. L. (1995). Relationship between the Bracken Basic Concept Scale and the Differential Ability Scales with an at-risk sample of preschoolers. Psychological Reports, 75, 219-224.

Bracken, B. A., & Howell, K. K. (1991). Ipsative subtest pattern stability of the Bracken Concept Scale and the Kaufman Assessment Battery for Children in a preschool sample. School Psychology Review, 20(2), 315-330.

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ADHD conference @ Johns Hoplins

Although this conference overlaps with a few early days of the annual NASP convention in NY, I just received a mailing for a conference that looks to be a comprehensive look at ADHD. Johns Hopkins School of Medicine is sponsoring "The spectrum of developmental disabilities XXIX: ADHD--Beyond the basics" on March 26-28, 2007. The conference program looks impressive.

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Random tidbits from mind blogsphere 12-13-06

  • Thanks to ENL blog for FYI regarding new Stanford study that suggests that the brains of dyslexic readers "work harder" to read.
  • Lifehacker has a post on "15 unusual ways to use Google"
  • Thanks to Mind Hacks for the tip that Synapse 13, a psychology and neuroscience writing carnival, has appeared online.
  • Brain Fitness Center news release by Sharp Brains
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Sunday, December 10, 2006

Blog status - blogmaster has been recovering

Regular readers may have noticed a dip in my blog activity the past 1.5 weeks. As noted previously, I alerted readers to the fact that I was going to be "on the road again." That expected decrease in blog activity was extended for a longer period of time due to my involvement (as a passenger) in a car accident on 12-1-02.

Without getting into details, I've been dealing with some back, neck and shoulder pain and muscle problems this past week and have found it difficult to focus on work, partially due to the side effects of the pain medication and my increased need to sleep and rest. This weekend I believe I've rounded the corner with regard to the pain and my need for extra rest. I hope to gradually increase my blogging activity this week.

Thanks for your patience. The good news is that the hit counter for this humble blog has remained steady...which provides me the motivation to get back in the bloggin' saddle.

Recent literature of interest 12-10-06

This weeks recent literature of interest can be found by clicking here.

I'm now experimenting with listing the references by journal title...I find it easier when looking up articles via the university library.

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Friday, December 08, 2006

Identifying gifted minority students

I've always been a big fan of the "aptitude" work of the late Richard Snow. One of his students, David Lohman, continues to publish good stuff in the same vein, as well as solid intelligence and psychometric research.

I recently stumbled across a brief "newsie" type publication by Lohman at the Riverside Publishing web site dealing with the identification of academically gifted minority students (click here). D. Lohman is also listed under the "IQs Scholars" section of this blog. If you visit his web page, you will see that he has made numerous articlesavailable for downloading. Good stuff.

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Thursday, December 07, 2006

Reading happy?

Interesting review of study at Cognitive Daily that suggests that thinking faster, vis-a-vis reading faster, may elevate feelings of happiness.

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Advertising on IQs Corner blog

Yesterday I made a post re: the opening up of advertising space on my blog via a professional service. I have had a few initial inquiries, and as per usual, the requests wanted to negotiate something a bit different than that offered by the service. Thus, I've changed my mind. I'm going to cut out the middle man and handle all the ad space work myself. This will allow me to respond more flexibly to possible advertisers.

First...why am I offering ads at this point in time?

Simple. I LOVE blogging. IQs Corner (and now the sister blog...Tick Talk Tock: The IQ Brain Clock) are real labors of love..and are, more-or-less, hobbies. However, I'm not able to spend as much time as I would like with this blog. If I had the time I could be posting considerable more material and could add new features. However, blogging comes at the expense of other work, projects, contracts, etc....all that pay the bills. Long story short---If this blog could generate a little "ching" in my pocket, I could then rationalize stealing time from other activities and do more.

With that in mind, the purpose of this note is to alert potential advertisers(e.g., individuals, educational and/or psychological publishing companies, book publishers; organizations, etc.) that it is now possible to place simple ads on IQs Corner at an introductory blow-out rate [contact me for details]. This is a deal! If this works and traffic continues to increase, the rates will increase. So...get in while the gettin' is good. I will change the rates when I see fit. The current rate is a bargain. If you are an advertiser and want to make me a "creative proposal" (multiple ads; more than six months)...then fire away. Contact me at

Why should anyone consider advertising on this blog? A few random pieces of data below:

  • You can't beat the introductory ad rate. [Or, make me an offer I can't refuse]
  • IQs Corner blog traffic continues to increase. A review of the hit counter information suggests the recent traffic upswing was largely due to increased recognition of this blog in the on-line internet encyclopedia - Wikipedia. This blog is now listed as a resource under the Wiki topics of "intelligence" and "intelligence quotient/iq." These highly visible links are providing constant new traffic to IQs Corner.
  • If you "Google" such terms/phrases as intelligence testing, CHC theory, and/or Cattell Horn Carroll, you will see that either this blog, or the IAP home web page (which in turn links to IQs Corner), typically show up on the first page of the Google search results. This blog, and the related IAP web site, has an established internet presence in the field of intelligence theories and testing, psychological theory, educational and school psychology, neuropsychology, etc.
  • Your ad money should reach a group of readers who are interested in staying abreast of contemporary research in intelligence theories, intelligence testing, educational psychology, school psychology, special education, and general psychological and educational theory and assessment.
  • You would help a great guy keep his hobby going :)
Advertising rates are currently set at the introductory rate. As traffic increases at this site, it is possible that these rates may be increased (they will be reviewed quarterly). If you are an advertiser and want to place multiple adds or want to sponsor an add for more than six months, then lets "talk turkey" about possible special rates.

The placement of an ad does not imply endorsement of the advertising company or products by Kevin McGrew, the Institute for Applied Psychometrics, or IQs Corner Blog. It is just a way to try keep this blog hobby viable.

Let the games begin. This is an experiment. I hope this "back scratch" works for all involved.

Email contact:


IQs Corner Headlines from mind blogsphere 12-7-06

All the news thats fit for IQs Corner readers:

This is the 13th installment of IQs Corner Headlines from the Brain and Mind Blogsphere

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Random tidbits from mind blogsphere 12-7-06

  • The way men dance is determined by how much testosterone they were exposed to in the womb? Check out the BPS Research Digest post
  • The DI blog continues its posts on executive function, this time a summary and comments about a recent factor analysis study of measures of EF in a sample of 102 adults with traumatic brain injury.
  • As per usual, the ENL blog has a nice post, with extensive resource links, regarding recent research regarding the neuropsychology of word retrieval/finding problems
  • Just in time for your XMAS shopping for the techie in your life....a brain mouse.
  • Interesting news article on "juicing the brain" over at Scientific American.

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Flynn Effect and Ravens test webcast

The Raven Progressive Matrices and the Flynn Effect: Review and Recent Research . Thursday, December 7th 2:30 PM Central Standard Time (Minneapolis/Chicago time)

  • For more than 20 years, it has been known that IQ is increasing in many countries around the world at the rate of about three standard score points per decade. For the same length of time, debate has raged over the underlying causes and meaning of this effect. While the degree of improvement is not uniform, and there is some suggestion that the effect may be diminishing or reversing in some regions, the "Flynn Effect" nevertheless is accepted as a real phenomenon that defies simple explanation.
  • In this special, 90 minute presentation, Dr. John Raven of the University of Edinburgh, will present wide-ranging data Raven Progressive Matrices normative studies --and a host of other sources--to provide a compelling explanation of the Flynn effect and address recent claims that the effect may be diminishing. This will be a remarkable lecture by a speaker whose grasp of source material is almost unparalleled.
  • Dr. Raven is presenting as a special lecturer for the University of Minnesota Medical School Psychology Internship didactic seminar series, however, all are invited to attend live or tune-in via the webcast. The event occurs on Thursday, December 7th, 2:30 to 4:00 CST. Room 12-109/12-115, Phillips-Wangensteen Building, University of Minnesota Medical School campus.
  • View the webcast by clicking here. You may log in as a guest. You may be prompted to install the Breeze meeting add-in. Remote attendees will be able to submit questions via the "chat" interface. The webcast will be recorded for later viewing.
  • For more information, contact Steve Hughes at 612-625-4287 or
  • Thanks to the TOVA Company for providing equipment used for this webcast.
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Tuesday, November 28, 2006

On the road again

I'm on the road for business starting tomorrow (11-28-06) and will return late Friday (12-1-06). Blog posts may be minimal. I shall return.

Tech tidbit - Gv oriented search engine

Thanks to Lifehacker for the FYI regarding an interesting new search engine that returns visual screen shots of the search results. I like it.

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Monday, November 27, 2006

Blog index Gf update

I decided to return to my attempt to go back through old posts and add topic "labels" to old posts, so the topic label index feature of IQs Corner would be more comprehensive. This evening I finished off all the Gf (fluid intelligence) related posts I could find.

For those who receive automatic RSS feeds from IQs will be receiving "false alarms" that suggest new posts. However, this may be a blessing in disguise. When going back through the archives I found many posts I had forgot about...some which include important stuff.

I will, on a very inconsistent basis, continue with this back-label indexing of IQs Corner...when the mood strikes me

ISIR 2006 program available

The International Society for Intelligence Research (ISIR) 2006 program is now available for viewing (click here). The conference is this December in San Francisco. Registration information can be found at the ISIR link above.

I'm officially PUMPED after looking at the program. It should be a great conference.

Please note that the ISIR home page is currently under a state of revision and many of the links are currently not active.

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Comments on the achievement gap

Interesting thoughts and analysis over at the Quick and the ED regarding national trends in narrowing the "achievement gap" reflected in changes in the most recent NAEP test scores.

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Grow a brain in a jar

Thursday, November 23, 2006

Recent literature of interest 11-23-06

This weeks recent literature of interest can be found by clicking here.

I'm now experimenting with listing the references by journal title...I find it easier when looking up articles via the university library.

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Wednesday, November 22, 2006

IQs Corner Headlines of mind blogsphere 11-21-06

All the news thats fit for IQs Corner readers:

This is the 11th installment of IQs Corner Headlines from the Brain and Mind Blogsphere

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Black-white IQ gap: Flynn and Murray present

I just learned of a special conference presentation (next week in DC) sponsored by the American Enterprise Institute (AEI) that will feature James "Flynn Effect" Flynn and Charles "Bell Curve" Murray presenting and discussing new research on the "Black-White IQ Gap: Is it Closing? Will it Ever Go Away?" Follow the links for additional information. The program abstract is presented below:
  • For decades, the difference in the test scores of blacks and whites on the SAT, National Assessment of Educational Progress test, Armed Forces Qualification Test, and traditional IQ tests has been a vexed issue for American educational policy. Two of the leading scholars of this controversial topic, James R. Flynn of the University of Otago (New Zealand) and Charles Murray of AEI, will debate the causes of the difference, its implications, and recent trends. New studies of the subject by Professor Flynn and by Mr. Murray will be available for distribution at the session.
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Do the sexes use different brain areas when "planning"?

Mixing Memory has a VERY interesting post regarding recent studies of possible gender differences in "planning" ability (part of executive functioning), as measured by the classic Tower of London task. MM's post speaks for itself. Of particular interest are findings suggesting no manifest performance difference between genders, BUT, significant differences in the areas of the brain's used (based on fMRI analyses). Check it out

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Tuesday, November 21, 2006

CHC theory: Crystallized intelligence (Gc)

[Note...this is the second in a series of posts I hope to continue in order to provide updated definitions of the major abilities in the Cattell-Horn-Carroll (CHC) theory of cognitive abilities. See Gf prior post]

The prior knowledge an individual brings to a new task influences their performance on the task. It is commonly assumed (an assumption validated via research) that is much easier to learn and remember something if we have an existing knowledge framework in which to embed the new knowledge (Engle, 1994).

Crystallized intelligence (Gc) is one of the primary human domains of acquired knowledge. Both laypeople and experts agree that Gc is an important part of overall intellectual ability. Gc represented by such behaviors as “displays a good vocabulary,” “reads with high comprehension,” “is verbally fluent,”and “converses easily on a variety of subjects,” was found by Sternberg, et al. (1981) to be the first of three major factors defining intelligence for both experts in the field of intelligence and laypeople (Campito, 1994).

According to the APA Dictionary of Psychology, crystallized abilities are those abilities "such as vocabulary and cultural knowledge, that are a function of learning and experience in a given culture. Crystallized abilities are believed to depend on physiological condition somehwat less than do fluid abilities; thus they may be better sustained in old age. They are also believed by some to derive from fluid abilities." (p. 248)

Crystallized Intelligence (Gc) is the breadth and depth of a person's acquired knowledge of a culture and the effective application of this knowledge. According to Horn (1994), "Gc can be thought of as the intelligence of the culture that is incorporated by individuals through a process of acculturation" (Horn, 1994, p.443). This store of primarily verbal or language-based knowledge represents those abilities that have been developed largely through the “investment” of other abilities during educational and general life experiences (Horn Noll, 1997).

Schematically, Gc might be represented by the interconnected nodes of a fishing net. Each node of the net represents an acquired piece of information, and the filaments between nodes (with many possible filaments leading to and from multiple nodes) represent links between different bits of stored information. A person high in Gc abilities would have a rich “fishing net” of information as represented by many meaningfully organized and interconnected nodes. Gc is one of the abilities mentioned most often by lay persons when they are asked to describe an “intelligent” person (Horn, 1988). The image of a sage captures to a large extent the essence of Gc.

According to Gilhooly (1994), when discussing the knowledge domains (in this case, Gc), certain distinctions generally recur: (a) knowing that versus knowing how, (b) declarative versus procedural knowledge, (c) explicit versus implicit (tacit) knowledge, and (d) semantic versus episodic knowledge/memory. The first three distinctions are virtually synonymous. “Knowing that” (i.e.,declarative, explicit knowledge) is consciously known and can typically be expressed in a commonly understood code (e.g., spoken or written language) or in some form of specialized code (e.g., notation in music or dance movement.). “Knowing how" (i.e., procedural, or implicit, knowledge) is not accessible consciously. Although procedural knowledge can be demonstrated in behavior, it is not explicitly communicable. Gc includes both declarative (static) and procedural (dynamic) knowledge. The final Gc knowledge distinction (semantic vs. episodic knowledge) differentiates between knowledge of general concepts, principles, and word meanings (semantic knowledge) versus autobiographical knowledge of specific experiences (episodic knowledge) (Gilhooly, 1994).

Declarative knowledge is held in long-term memory and is activated when related information is in working memory. Declarative knowledge includes factual information, comprehension, concepts, rules, and relationships, especially when the information is verbal in nature. For example, during pre-clinical training, a medical student acquires declarative knowledge about diagnosing clinical problems—the student learns factual information, concepts, rules, and relationships.

Procedural knowledge refers to the process of reasoning with previously learned procedures in order to transform knowledge. For example, during the second phase of medical training, when medical students study a patient's case, current information in short-term working memory triggers the student to retrieve declarative knowledge and apply it to the patient. Applied declarative knowledge is procedural knowledge.

An individual with poor Gc lacks information or language skills or has an inability to communicate (especially verbally) his or her knowledge. Such a weakness can produce cumulative learning problems as it becomes increasingly difficult to learn from what one is reading or hearing if the words, vocabulary, and concepts in the material are not in a reader’s existing fishing net of knowledge. That is, it is hard to relate and connect a new “node” of information to a net of knowledge where no similar nodes exist. We would all most likely fail a course in quantum physics as few of us have a net of knowledge that includes the “prerequisite” nodes of information to make sense of the new material. The concept of academic course prerequisites reflects an awareness of the importance of prerequisite knowledge in a domain.

Given the limited capacity of working memory, formal human knowledge domains (Gc, as well as other acquired knowledge domains such as Grw, Gq, Gkn), seek "cognitive economy in terms of rules or principles with the widest range and the maximum simplicity." Gilhooly (1994, p. 637). This preference for simplicity (to minimize cognitive effort) can result in over-simplifications at the cost of inaccuracies. Furthermore,because people can only actively focus attention on a limited amount of their vast store of acquired knowledge at any one time, knowledge (e.g., Gc) tends to be organized into hierarchical structures. The hierarchical organization of knowledge helps insure that associations to related information are strongest (Gilhooly, 1994; p.637).

The breadth of Gc is apparent from the number of narrow abilities that it subsumes.

In the arena of intelligence research, Gc has been likened to the wallflower ability. See comments by Earl Hunt for clarification.

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