Benefits of early childhood interventions across the world: (Under) Investing in the very young

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Abstract

This paper reviews the international (non-U.S.) evidence on the benefits of early childhood interventions. A total of 38 contrasts of 30 interventions in 23 countries were analyzed. It focuses on studies applying a quasi-experimental or random assignment. Studies were coded according to: the type of intervention (cash transfer, nutritional, educational or mixed); sample size; study design and duration; country; target group (infants, prekindergarten); subpopulations of interventions; and dosage of intervention. Cohen's D effect sizes were calculated for four outcomes: cognitive gains; behavioral change; health gains; and amount of schooling. We find children from different context and countries receive substantial cognitive, behavioral, health and schooling benefits from early childhood interventions. The benefits are sustained over time. Interventions that have an educational or stimulation component evidenced the largest cognitive effects.

Introduction

The last several decades have seen a growing interest in public investments in children at early ages around the globe (Choi, 2004, Kirp, 2007, OECD, 2006). A primary source of this interest is growing knowledge and awareness of the importance of environmental influences on development, particularly, but not only on cognitive development, during the early years (Cunha, Heckman, Lochner, & Masterov, 2006). Information on the loss of potential intellectual development in these years, stunting, and early emergence of gaps between more and less advantaged groups have pointed to the importance of targeting children in the first 5 years of life to increase later developmental and educational outcomes. Although there is increasing agreement about the importance of intervening to improve early development, there is less agreement about the most effective and efficient ways to improve early development. In the case of developing, low-income countries there has been particular interest in combining education with other interventions that prevent malnutrition and stunting given the irreversibility of early nutritional insufficiencies (Agüero, Carter, & Woolard, 2006).

Across countries, early childhood education and care providers differ tremendously. Preschool programs may focus on one or several of the following aspects of children's growth and development: physical growth and health, mental health, nutrition, language and cognition, and social and emotional development. These programs may take place in formal, informal and non-formal settings, and they can be center-based, formal preschools, parent/community-based arrangements, or home-based arrangements. In addition, impacts on maternal employment are important for many programs as these (at least potentially) generate income that might enhance early childhood development and in some countries policy emphasis has been on child care with employment and child development viewed as joint products. Coverage has increased dramatically in the developed world over the last three decades, but progress in the developing world has been uneven and slow (UNESCO, 2006). Much of the growth in funding for programs has been due to expansions by the public sector, yet child care continues to be mostly privately provided and is often provided by caregivers with little or no formal preparation and low levels of education. Particular interventions, such as those that will be reviewed in this paper, vary in a number of aspects, including intensity, staff qualifications, quality of services, and, not unexpectedly, effectiveness.

A central question for policymakers in the current context is what types of programs are cost-effective, and, in particular, whether to provide interventions with a single focus on child care services only, education, nutrition or health care, or some combination of these, either through multiple programs or a single multi-purpose program (UNESCO, 2006). Answering this question can be quite involved as it is to be expected that effectiveness will vary with the broader conditions in which children live and develop, including such circumstances as the availability and quality of later schooling. A growing body of research provides relevant information for policymakers. It is important to use the research not only to obtain evidence regarding whether (early childhood education and development) ECD programs have impacts, but also the extent to which child outcomes vary with the intensity and duration of ECD investments. In other words, in addition to asking “what kinds of preschool intervention, if any, are effective, attention should [be] given to the question of what amount of treatment yields what amount of gain” (McKay, Sinisterra, McKay, Gomez, & Lloreda, 1978).

Research from the United States going back many years has provided evidence that intensive, high-quality early childhood interventions have direct and persistent effects on cognitive and non-cognitive development (Barnett, 2008, Blau and Currie, 2005, Camilli et al., in press, Heckman and Masterov, 2007, Temple and Reynolds, 2007). Important short- and long-term effects across various dimensions of child development have been found in multiple randomized trials with interventions as varied as part-day preschool education at ages 3 and 4, full-day educational child care birth to age 5, and home visitation beginning prenatally. Income supplements and comprehensive services programs have had relatively disappointing results for the most part, though some suggest that modest gains in achievement follow from even small increases in income (Barnett, 2002, Dahl and Lochner, 2008, Duncan, 2005, Lucas et al., 2008).

In the international arena, there is a consensus on early childhood interventions having developmental benefits in early childhood (Engle et al., 2007, Vargas-Barón, 2009, Vegas and Santibañez, 2008). However, the studies that are the basis for this consensus vary in method, population, type of intervention (e.g., nutrition, education, parenting education, income supplementation, countrywide or localized1), and type of outcome measured (anthropometric, cognitive, behavioral, school readiness and progress, inter alia), with some outcomes being short-term and some long-term. Traditional reviews have not gone beyond the general consensus to tackle the difficult problem of trying to understand what else might be learned from the variation in methods, interventions, national contexts, and outcomes. Meta-analysis provides a means to summarize studies’ outcomes on a common scale in ways that may help us understand more about how best to design intervention policies and programs. To our knowledge, no meta-analyses of early intervention have been conducted for studies done outside the United States, and there is a lack of analyses that consider the effects of research design, context, services provided (stimulation, nutrition, care, preschool, cash transfer), duration, age of intervention, and other key elements of early intervention program design.

This paper reviews the evidence from outside the United States and Canada in such a way as to examine the studies along comparable dimensions and with outcomes translated into a comparable scale. We summarize research on short- and long-term effects of a wide range of early childhood interventions. We group results from these international studies into four outcome domains: cognition, behavior, health, and amount of schooling. The review examines outcomes from 38 contrasts which employed rigorous quasi-experimental or randomized designs to evaluate the effects of 30 interventions in 23 countries. To compare contrasts we constructed a detailed dataset of the outcomes containing information on outcomes and study characteristics. Outcomes were converted to effect sizes (Cohen's D) providing a single scale for use in summarizing the results. This dataset includes estimated effects across types of intervention (nutrition, nutrition and education or stimulation, cash transfers), and along different domains of a child's development (cognitive, behavioral, health and schooling), and differentiates outcomes based on the time of the follow-up beyond the end of the intervention and several other study characteristics.

Through meta-analysis we explore and estimate the impact of early childhood interventions in cognitive, behavioral, health and schooling domains, and assess how the characteristics of the intervention and the target population are associated with such impacts. We find moderate benefits across all four domains and evidence that effects were sustained over the longer run. We observe that educational or mixed interventions (with educational, care or stimulation components) have the largest cognitive effects compared to cash transfers or solely nutritional interventions and smaller effect sizes for higher quality design (e.g. randomized).

Section snippets

Methodology

We collected information on interventions in developed and developing countries through computer-aided searches and reviews of reference lists in the studies identified. Year of intervention did not matter for inclusion and interventions were mostly published in early childhood or nutrition journals, but publication in a peer-review journal was not a requirement for inclusion, and the broader “grey” literature was searched to reduce potential effects of publication bias.2

Effect sizes by selected design and population characteristics

Table 1 summarizes the basic findings for each of the four outcome domains across all of the interventions and follow-up periods. The overall mean Cohen effect size across the 38 contrasts is of 0.29 (SD 0.28). The mean average effect size for cognitive outcomes is 0.31 (SD 0.21). The mean effect size for the other outcomes is similar: behavior is 0.27 (SD 0.24), health is 0.31 (SD 0.41); and the mean for schooling outcomes is 0.27 (SD 0.31).5

Conclusions and discussion

A total of 56 studies reporting the effects of 30 interventions (and 38 contrasts) in 23 countries in Europe, Asia, Africa, Central and South America are analyzed. This review includes quasi-experimental and randomized studies. We coded studies on the type of intervention (cash transfer, nutritional, educational or mixed), the sample size of the control and treatment group, the study design, the country of intervention, subpopulations of interventions, follow-ups, whether it targeted infants,

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