The proposal of this article is to present and discuss the methodology applied in the frame of a socio-anthropological research held in Bolivia and Peru on child development and growth. The objectives of the investigation were to study the mother's perceptions (and those of other related caretakers, i.e. fathers) on their child's illness and health. The idea was to: (i) identify and understand the health problems such as perceived by the caretakers; (ii) to identify strategies and therapeutical itineraries within the local health system (hospital, healers, sorcerer); (iii) to analyse the power relations within the family of the children and between the other actors of the system in relation to the child's health. To reach these objectives, an in-depth classical socio-anthropological study was conducted (semi-structured and open interviews, observations) among the health personal (nurses, doctors, local health promoters) and caretakers. But other more innovative tools were also applied during the research process, such as the use of the causal model as a support for focus group discussions. Characteristics, advantages and limits of this tool combination are exposed and discussed in the article, following the questions mentioned above: (i) What are the advantages to use a causal model as a support for a focus group discussion? Which are the difficulties and the necessary adaptations?; (ii) What are the advantages and limits of working with students for this kind of experimentation?; (iii) What are the lessons of this combination for the conduct of an in-depth socio-anthropological study? Under what conditions is it possible to articulate the tools? ; (iv) To what extent is it possible to reproduce this experience?