Ernest Madu Rocks too...

Yup, two TED talks in a row. Talk about lazy blagging. Nod to the Sceptical Alchemist where I first saw this one.

Preschool Programs Can Boost School Readiness

In an earlier post on the Durable effects of concentrated disadvantage on verbal ability among African-American children I reported some rather depressing, if excellent, research measuring the cognitive penalties children suffer along with, and likely as consequences of, serious disadvantage. There's some relevant good news in this short paper by Gormley, Phillips and Gayer. (Also available at the publications section of the site of the Crocus project.)

This time around the data reports that specific pre-school programs among pre-school children leads to significant gains in scores on tests that are regarded as good predictors of later school achievement. Two programs. both in Tulsa, Oklahoma, were studied - the Head Start Program, and the Oklahoma pre-K program. Each differ in how they work (the differences are briefly described in the paper) and Oklahoma was selected partly because:

The Oklahoma pre-K program has relatively high standards compared with those of other states and offers relatively high pay and benefits to well-qualified teachers. Every lead teacher must have a B.A. degree and must be certified in early-childhood education. Student teacher ratios of 10-to-1 and class sizes of 20 must be maintained. The Community Action Project (CAP) of Tulsa County, whose Head Start program serves the largest number of children in Tulsa, is eligible for state funding. Its teachers meet the same standards as their Tulsa Public Schools (TPS) counterparts and receive similar pay (p1723).

To avoid selection bias students who'd attended were compared with students about to attend the respective interventions. Variation in ages at start allowed the relationship between age and test scores either side of the age cut off for entrance to be estimated. The analysis also conditioned on indicators of poverty and race, and found program participation to be a more powerful predictor of success. The results are impressive. Here's another quotation:

The TPS pre-K program has sharply improved students’ cognitive development.
One way to capture this is to look at the effect sizes: 0.985 for letter-word identification, 0.743 for spelling, and 0.355 for applied problems. These effect sizes substantially exceed those reported for pre-K programs generally and are somewhat greater than those reported for five states with relatively high quality pre-K programs. The effects of the Tulsa Head Start program, though less spectacular, are also impressive: 0.514 for letter-word identification, 0.334 for spelling, and 0.369 for applied problems. These effect sizes exceed those reported for a national study of Head Start with random assignment of children.

Then take a look at the figure, converting the measured gains into monthly equivalents. These figures are, according to the paper, greater than those (not represented in the graph) occurring through maturation.

Cool. Well resourced educational programs with qualified instructors and good pupil-teacher ratios actually do some good. Also, they do good even with kids who we've got good reason to expect have been cognitively harmed by their environments. That's hardly surprising, but it's good to get a sensible measure of it, especially with all the flaky opinionated yelling that goes on over education.

As with the paper by Sampson, Sharkey and Raudenbush I referred to previously, a key feature of this research is the construction of a large enough sample, with appropriate differentiation within it, to extract meaningful data with statistical tools. The more social science like this we see the better.

Gormley Jr., W.T., Phillips, D., Gayer, T. (2008). THE EARLY YEARS: Preschool Programs Can Boost School Readiness. Science, 320(5884), 1723-1724. DOI: 10.1126/science.1156019

Durable effects of concentrated disadvantage on verbal ability among African-American children

This paper in PNAS opens noting that there's broad consensus that "cognitive ability predicts adult well-being across a variety of dimensions, whether educational attainment, labor market success, avoidance of criminal behavior, or health. There is also increasing agreement that cognitive ability is significantly shaped early in the life course, such that a focus on children is essential" (p 845).

There's also some controversy about the precise extent to which the course of early development determines cognitive ability, with some researchers (for example Herrnstein and Murray in The Bell Curve) arguing that differences in adult intelligence between populations are to a significant extent genetically based. I'm not going to try to say anything about the wider issues here, but this paper by Sampson, Sharkey and Raudenbush is an important contribution.

They key idea behind the research is an attempt to study the neighbourhood as a determinant of cognitive ability. There are several good reasons for this, reviewed in the paper, including that neighbourhood poverty is associated with inconsistent parenting, and poor mental health in parents. There are also ways in which marginal and violent neighbourhoods might be expected to compromise quality of speech communication, and in other ways limit opportunities for learning. The authors therefore hypothesised that "residing in a severely disadvantaged neighborhood cumulatively impedes the development of academically relevant verbal ability in children" (p 846).

There are non-trivial methodological problems in attempting to measure effects here. Some relate to analysis. Controlling for income, for example, while sensible in some ways amounts to hypothesising that neighbourhood doesn't itself have an effect on income, or at least reduces the chance of detecting multiple determinants of different cognitive ability. The present study attempts to deal with this in ways I’ll get to in a moment. There are also problems with selection of subjects, since the majority of studies are cross-sectional. The authors of this study opted to compare within-individual changes as related to stability or change in neighbourhood as a way of avoiding the limitations of cross-sectional approaches.

The study followed 2000+ children, living in Chicago, between the ages of 6–12. The subjects, along with their caretakers, were followed when they moved for up to 7 years. As the authors put it:

Approximately 17% of black children not living in disadvantage in 1995 moved to a disadvantaged neighborhood some time between 1995 and 2002, and 42% of the population of black children living in disadvantaged neighborhoods in 1995 moved to a nondisadvantaged neighborhood between 1995 and 2002. We exploit these ''within-individual'' changes to estimate the causal effect of moving (p 846).

Leaving out a lot of important detail, the study proceeded as follows neighbourhoods were classified into levels of disadvantage using Census data, and subjects' trajectories classified according to a series of 'waves' giving a number of sequences (e.g. disadvantage, nondisadvantage or nondisadvantage, disadvantage). Baseline disadvantage (wave 0) was not regarded as a 'treatment' but subsequent waves were. The different trajectories were related to a measure of cognitive ability combining the Wechsler Intelligence Scale for Children vocabulary test and the Wide Range Achievement Test reading examination. Subjects were selected from nearly 35,000 households, and interviewed and assessed three times over a seven year period.

For various reasons the published analysis, concerning 'concentrated disadvantage' focuses on the African-American subjects. (Concentrated disadvantage was defined as neighbourhoods falling in the bottom quartile of a distribution factoring in six elements of the Census data.)

The most important finding, and the one noted in the title of this paper, is represented in this graphic. It compares cognitive ability scores of children who started out in neighbourhoods with concentrated disadvantage and remained there for both waves of the analysis with those of children who started in the same position but moved away from concentrated disadvantage for wave 2. Again quoting from the paper "Scores for black children who lived in such neighborhoods declined sharply relative to the average rate of growth in the sample as a whole, so that by wave 2, their verbal ability scores are well below the mean and_4 points below those of black children who do not experience the treatment" (p 851).

This is mixed news. It's lousy that it seems as though early disadvantage is so harmful. (The authors are cautious about extrapolating without additional justification from their results, but it's still lousy, and only more so if extrapolation is warranted.) On the other hand, it suggests where to focus at least some policy attention: fix the places kids grow up.

The paper is also currently available on Sampson's website here.

Sampson, R.J., Sharkey, P., Raudenbush, S.W. (2008). From the Cover: Inaugural Article: Durable effects of concentrated disadvantage on verbal ability among African-American children. Proceedings of the National Academy of Sciences, 105(3), 845-852. DOI: 10.1073/pnas.0710189104