This study longitudinally examined the interplay between birth-order and well-known risk factors in impoverished environments such as inadequate environmental stimulation, low maternal education, and young maternal age in children from birth to 36 months. In the developmental motor domain, the effect of the stimulating environment over time, favored first-borns. In the adaptive domain, maternal education privileged first-born boys. In language development, first-borns reached higher scores over time than laterborn identifying a positive impact of stimulation. In the personal-social domain, firstborns obtained higher averages overall, but stratified models revealed that later-borns reached the first-borns scores as maternal age increased.

这项研究纵向研究了贫困环境中出生顺序与众所周知的危险因素之间的相互作用，例如环境刺激不足、母亲受教育程度低以及出生至 36 个月儿童的母亲年龄较小。在发育运动领域，随着时间的推移，刺激环境的影响有利于长子。在适应性领域，母亲教育优先考虑长子。在语言发展方面，随着时间的推移，第一个出生的孩子比后来出生的孩子取得了更高的分数，认为刺激具有积极的影响。在个人社会领域，长子的总体平均得分较高，但分层模型显示，随着母亲年龄的增加，后来出生的孩子的得分达到了长子的分数。