Critique of Vreugdenhil et al.'s study linking PCBs to the play behaviors of Dutch girls and boys. (Correspondence).
The PSAI has weak psychometric properties. The test--retest reliabilities in the 0.60s are based on tiny samples of 15-18. The 1-year interval is too long to measure the stability of test scores; long intervals confound the test's stability with real changes in children's behavior. The split-half reliability is adequate for girls (0.80) but poor for boys (0.66). Golombok and Rust (1993b) provided split-half reliability for the total sample, and they hailed the value of 0.88 as "robust." However, that value is spuriously high because of the bimodal distribution of test scores when combining sexes. Interestingly, Golombok and Rust (1993b) noted that the value of 0.84 for the test-retest reliability of the combined sample of 33 boys and girls is spuriously high because of bimodality; that argument also applies to split-half coefficients.
The construct validity of the PSAI is suspect. Golombok and Rust (1993b) failed to match socioeconomic background of mothers of boys with that of mothers of girls, and they based the final instrument on data from 32 boys and 43 girls, samples too small to yield generalizable data. They provided only a single PSAI validity study, despite subsequent testing of > 2,000 parents of young children; also, validity data from London may not generalize to data from the Netherlands.
Also, Vreugdenhil et al. (2002) reported no studies to validate the parents' perceptions--they did not actually observe children's play activities, an essential aspect of test validity, as Golombok and Rust (1993b) noted for previous play-preference instruments. Parents' perceptions may be biased and require validation.
Vreugdenhil et al. (2002) interpreted the PSAI composite score (male items minus female items); however, PSAI psychometric data are provided only for the total score. Consequently, the reliability and validity data do not even apply to the "difference" score used by the authors; indeed, difference scores are notoriously unreliable. Golombok and Rust (1993a, 1993b) provided no data on the separate male and female items; Vreugdenhil et al. (2002) presented no rationale for analyzing data for the so-called masculine and feminine scales.
Vreugdenhil et al. (2002) inappropriately used the interaction term "sex x exposure" in their regression analysis. This analysis involves combined groups of boys and girls, a serious problem because bimodal distributions spuriously inflate correlations; that includes coefficients involving the sex x exposure interaction, conceivably explaining the "significant" PCB results. Also, Vreugdenhil et al. used age-unadjusted scores, fine for comparing boys with girls, according to Golombok and Rust (1993b), but requiring care "in the choice of appropriate statistics when [combining] data from both sexes ... in the same analysis" (p. 134). Vreugdenhil et al. (2002) did not heed this warning, again ignoring bimodal distributions.
The PSAI is likely not valid for school-age children. The average age of the Dutch children was 7.5 years, whereas the PSAI was developed and designed for preschool children; its oldest norms group is 60-71 months, much younger than the average age of the Dutch children.
Vreugdenhil et al. (2002) made many multiple comparisons, but they did not take the chance errors into account, a problem that affects many PCB studies (Cicchetti and Kaufman 2002; Kaufman 2002) and studies of lead level as well (Kaufman 2001, Phelps 1999), further compromising the meaningfulness of any reported significant effects. The authors related parents' perceptions of their young children's behaviors to sex steroid hormones but offered no direct evidence that PSAI scores are in any way related to sex steroid hormones--nor have Golombok and Rust made such claims for their test.
Vreugdenhil et al. (2002) referred to the Yu-Cheng sample and inferred that gender differences on Raven's Matrices tests are evidence of sex-specific differences in spatial ability. This is an error; Raven's tests primarily assess reasoning ability, not spatial ability. Spatial tests such as Block Design do produce sex-specific results (Jensen 1980), but sex differences are not usually found with Raven's tests or similar matrices tests [see Table 4.33 in Kaufman and Kaufman (1983)].
Overall, Vreugdenhil et al. (2002) used a flawed instrument and made other methodological errors that should cause them and other researchers to question their significant findings and their conclusions.
REFERENCES AND NOTES
Cicchetti DV, Kaufman AS. 2002. Does PCB exposure have any effect on later psychomotor and mental development? [Letter]. Lancet 359:1438.
Golombok S, Rust J. 1993a. The measurement of gender role behaviour in pre-school children: a research note. J Child Psychol Psychiatry 34:805-811.
--. 1993b. The Pre-school Activities Inventory: a standardized assessment of gender role in children. Psychol Assess 5:131-136.
Jensen AR. 1980. Bias in Mental Testing. New York:Free Press.
Kaufman AS. 2001. Do low levels of lead produce IQ loss in children? A careful examination of the literature. Arch Clin Neuropsychol 16:303-341.
--. 2002. PCB-induced impairments in older adults: critique of Schantz et al.'s methodology and conclusions [Letter]. Environ Health Perspect 110:A70-A71.
Kaufman AS, Kaufman NL. 1983. K-ABC Interpretive Manual. Circle Pines, MN:American Guidance Service.
Phelps L. 1999. Low-level lead exposure: implications for research and practice. Sch Psychol Rev 28:477-492.
Vreugdenhil HJI, Slijper FME, Mulder PGH, Weisglas-Kuperus N. 2002. Effects of perinatal exposure to PCBs and dioxins on play behavior in Dutch children at school age. Environ Health Perspect 110:A593-A598.
Alan S. Kaufman
Yale Child Study Center
Yale University School of Medicine
New Haven, Connecticut
*Current address: Escondido, California
The author has consulted for General Electric, but received no remuneration for any aspect of the preparation of this manuscript; he does not feel there is a genuine conflict of interest.
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|Author:||Kaufman, Alan S.|
|Publication:||Environmental Health Perspectives|
|Date:||Jun 1, 2003|
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