The importance of the first 5 years of life for long-term development is by now well-established. During this vital period many children - particularly in developing countries - are surrounded by poverty, and do not receive adequate physical, mental or emotional nourishment, with adverse consequences lasting right into adulthood.

There is increasing evidence that interventions in early childhood are very important for physiological and psychological development. However, if - as is often the case - they are implemented by experts outside the communities, they are expensive and infeasible to expand widely. In this research project we develop and evaluate a cost-effective and sustainable intervention to promote early child development. The intervention is being implemented using local community resources, thus providing a viable model for scaling up if successful. The setting is Colombia.

The intervention consists of weekly home visits - lasting around one hour - to mothers/primary carers of children aged between 1 and 2 years, for a period of one and a half years. The "home visitors" interact with carers and children - showing them age-appropriate games to play with children and toys to make for them using scrap materials from around the community and home - and discusses the importance of psychosocial stimulation for child development with the carer (following the model designed by Grantham-McGregor and successfully implemented in various countries). The home visitors are drawn from local female elected representatives ("madres lideres"), and receive extensive guidance and preparation for their role.

To evaluate the intervention, some communities have been chosen randomly to receive it, others not. Furthermore, we randomly provide nutritional supplements in some of the treated communities in order to test whether the intervention is more likely to be successful if children's nutrition is also targeted - an important ongoing debate. Surveys are being conducted twice - before the intervention starts (February-June 2010), and 18 months later when it ends. The main outcomes being measured are the children's motor, cognitive and socio-emotional development, and their health. To this end, we administer Bayleys tests to children before and after the intervention, as well as collect detailed data on their health status. We also obtain detailed information on various socio-economic characteristics of the household, in order to be able to understand the constraints that poor households face when making choices relevant to their children's development, and ultimately to investigate why the intervention works or not.