(introductory text...)

When the follow-up in Guatemala was being initiated in the late 1980s, there were no empirical data with which to assess the validity of the hypothesis we intended to test: to our knowledge, no studies had examined the relation between early supplementary feeding and adolescent cognition among nutritionally at-risk populations. Thus, the plausibility of our hypothesis had to be assessed from indirect evidence. In this chapter, we discuss two sets of data that were particularly relevant to this endeavor. One of these consists of studies that examined the effects of early supplementary feeding on mental development in early childhood and the other of evaluations of long-term effects of compensatory early childhood educational interventions on adolescent development.

The issue of plausibility also had to take account of contemporary views in developmental psychology and nutrition. Since the inception of the Guatemala longitudinal study in 1969, major changes had taken place in theories of human development. One critical change had been a move away from a main effect (biomedical) model of developmental risk. In contrast to views prevailing in the 1960s, it is currently recognized that, in general, exposure to a single risk factor in early childhood does not necessarily determine a developmental course; rather, the effects of exposure are often viewed as modified by multiple factors both in and outside the child. As such, contemporary views have increased the complexity of explanatory models and called into doubt the possibility that successful strategies for developmental intervention can be restricted to monofocal interventions.