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JC Denton
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http://www.udel.edu/educ/gottfredson/reprints/1997whygmatters.pdf
why g matters: the complexity of everyday life
excerpt:
World War II offers an early demonstration. During a period when it had to train many thousands of pilots, the military experimented with admitting to pilot training inductees of all ability levels (Matarazzo, 1972, p. 163). Of men in the top stanine of the experimental selection battery, which included abilities and motivation measured at induction, 95% successfully completed training, whereas only 20% of those in the lowest stanine did so. Subsequent military research has consistently shown that highly g-loaded measures such as the Armed Forces Qualifying Test (AFQT) and its forerunners, although not always conceptualized as measures of g, are good measures of “trainability’‘-hence their long-time use in screening for enlistment and assignment to training programs. More recent work, such as Army Project A (McHenry et al., 1990), has carefully demonstrated the validity of such measures for predicting job performance itself in military specialties.
Additional evidence of the causal importance of g is provided by the many unsuccessful efforts to eliminate or short-circuit its functional link (correlation) with job proficiency. For example, there have been efforts to train the general cognitive skills that g naturally provides and that jobs require-such as general reading comprehension (which is important for using work manuals, interpreting instructions, and the like). Another approach has been to provide extra instruction or experience to very low-aptitude individuals so that they have more time to master job content. Both reflect what might be termed the training hypothesis, which is that, with sufficient instruction, low-aptitude individuals can be trained to perform as well as high-aptitude individuals. The armed services have devoted much research to such efforts, partly because they periodically have had to induct large numbers of very low-aptitude recruits. Even the most optimistic observers (Sticht, 1975; Sticht, Armstrong, Hickey, & Caylor, 1987) have concluded that such training fails to improve general skills and, at most, increases the number of lowaptitude men who perform at minimally acceptable levels, mostly in lower level jobs.
Not even lengthy experience (5 years) eliminates differences in overall job performance between more and less bright men (Schmidt et al., 1988). A large study of military cooks, repairmen, supply specialists, and armor crewmen showed that performance may converge on simpler and oft-performed tasks (Vineberg & Taylor, 1972, p. 55-57). However, even that limited convergence took considerable time, reflecting large differences in trainability. It took men in the 10th to 30th percentiles of ability about 12 to 24 months to catch up with the performance levels on those tasks that were exhibited by men above the 30th percentile with no more than 3 months’ experience on the job. These findings from field settings are consistent with Ackerman’s (1987) review of the experimental literature relating skill learning and ability: individual differences in performance do not decrease with practice, and sometimes increase, when tasks are characterized by “predominantly inconsistent or varied information processing requirements .” In short, tasks that are not easily routinized continue to call forth g.
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