andria reyes has been working on the study since its inception. woman: i'm part of a large research team that collects data for this research study, and we're the people who are in contact on a daily basis with the mother-and-child pairs. at each visit, the mom gets interviewed -- we do several short questionnaires with her -- and the child gets tested neurodevelopmentally. this is all done through play, and it's pretty fun for the child. we're looking at mental and motor skills and we want to see if there are any delays in those skills. we want to see how they relate to any exposures the child may currently have or may have had in the past. what is a cow? narrator: one test done on 4 1/2-year-olds asks them to draw a person. these drawings are by children not exposed to pesticides. quite different from the ones by children who were exposed. but alone, results like these are not enough to make any definitive conclusions. dr. whyatt: to make sure that the effects you're seeing are, in fact due to the contaminant you're measuring you have to take in