Just under a decade later, however, Science published another paper that extended the scope of the MAOA findings. This time the data came from a major longitudinal study of a birth cohort of 1,037 children in Dunedin, New Zealand. The participants had first been assessed at three years of age and had just completed their ninth follow-up at the age of 26 years (4). Because mutations that lead to an absence of MAOA activity were unlikely to be present, the researchers examined 442 males in the group for differences in the promoter region of the gene, which determines how strongly the gene is expressed (that is, how much MAOA is produced). And rather than merely looking at the effect of MAOA levels on criminal behavior, the investigators explored the interactions of the participants' genetic endowments with their environmental circumstances. Specifically, the researchers were interested in how experiences of maltreatment between the ages of three and 11 years affected the later antisocial propensities of participants with either a high or low MAOA activity.