Are we getting smarter?
April 20, 1998
This forum's introduction
Questions answered in this forum:
Why do we still look at IQ scores? Is technology the cause of rising IQ scores? Has environmental or health factors increased IQ scores? Do current IQ tests reflect the idea of multiple intelligences? How does a person's race or socioeconomic background affect his or her IQ scores? Should student testing be changed to reflect the times? Viewer Comments
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A Gergen Dialogue with Howard Gardner, author of "Extraordinary Minds."
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November 26, 1996
Stephen Jay Gould talks about evolution.
Browse the NewsHour's coverage of law.
American Psychological Association
An online IQ test.
Scott Langley of Corvallis, OR, asks:
If average intelligence really is increasing, how much of this can be attributed to environmental and health factors such as better diet and the introduction of lead-free gasoline? Have studies been done looking at the contributions of these factors?
Prof. Alice Honig of Syracuse University responds:
Average intelligence is not increasing. Average means that the mean score on an intelligence scale is 100. Around that mean, the standard deviation of scores (for test-re-test, for example) is about 15 points for one standard deviation on either side of the score of 100. Children who are two or more standard deviations below the mean will have great difficulties in school learning and achievement. Let us be clear that there is a difference, although not totally strict and clear, between achievement tests, which measure what we know and have learned (these scores can indeed increase as people have more years of formal schooling!) and intellectual reasoning ability which can involve different content areas: such as mathematical, verbal, spatial, musical, artistic, dance/gracefulness, etc. Yes, different folks with about the same basic levels of general intelligence may have different gifts in many different domains. The theoretical physicist can manipulate matrices in multidimensional space...the Kabuki dancer can use his hands to create incredibly graceful motions in harmony with YO YO Ma's cello playing of Bach! (on public television a week ago).
In researches I carried out with Dr. Frank Oski, when he was chair of the Pediatric Department of Upstate Medical Center in New York State more than a decade ago, we found that babies and toddlers who had iron deficiency anemia (hemoglobin counts less than 10 g/dl) and who randomly received either a placebo or intramuscular iron, showed marked increase in IQ as measure by the Bayley scales one week later. I was entirely blind to the initial status of the infants and to which injection they received. Later, in a further study, we looked at groups of babies with hemoglobin greater than 11 g/dL ( thus without iron deficiency anemia) but some had biochemical or cellular indicators of iron deficiency. In this work, all babies were given intramuscular iron after receiving infant intelligence assessments. Retested one week later, the babies with the most severe iron deficits gained over 20 IQ points on the Bayley Mental Development Index. I, as examiner, was blind to the status of all babies. Even more awesome - those babies who had been crankiest and most solemn were the ones initially most severely iron deficited and 11/12 of those were able to be coaxed into grins and smiles as I retested them one week after initial assessment. Thus, the answer to your question, do nutritional status or environmental toxins impact on intelligence? Yes!
However, intelligence has motivational components and attentional components. It may well be that intelligence was not "raised" by the nutritional repletion. But the motivation to work hard at the problem solving tasks of the Bayley, and the Attention span and emotional resources to tackle each little challenging task the examiner presented were much improved by the nutritional repletion by intramuscular iron administration to each of the infants with nutritional deficits.
Prof. Ulric Neisser of Cornell University responds:
Yes, a number of psychometricians believe that the rise in test scores is chiefly due to improved nutrition and health. As evidence they point to the gains in height (and hence in head/brain size) that have occurred over roughly the same period of time. But other disagree: they note that (except in extreme situations) it is surprisingly difficult to show that nutrition has any effect on intelligence at all! Three expert contributors will address this question in separate chapters of "The Rising Curve", and no two of them agree.
I doubt, however, that the Flynn gains have much to do with the introduction of lead-free gasoline. The gains are occurring all over the industrialized world, whereas (to the best of my knowledge) most countries have not followed the U.S. move to non-leaded fuel.
Next: Do IQ tests reflect multiple intelligences?