in 1975, seitz, abelson, levine and zigler compared disadvantaged children enrolled and not enrolled in head start, using the peabody picture vocabulary test (ppvt). the participants were low-income inner-city black children whose unemployed, economically disadvantaged parents were considered unskilled. the head start children had attended for at least five months at the time of testing, including nine boys and 11 girls. the non-enrolled group was on the head start waiting list. the control group consisted of 11 boys and nine girls. the groups were matched by family income, parental employment and marital status. the tester tested children at home and in a school or office setting. the head start children scored higher than the controls in both settings, which suggested preschool intervention programs may have influenced the result. the controls tested at home scored the lowest, apparently due to anxiety from having an unfamiliar person in their homes. the head start children were unaffected by the environmental factor. in evaluating this study vs. others, the relatively small sample size should be noted: 20 children vs. thousands in other studies.