In this study, Drs. Lengua and Thompson examined growth in effortful control in relation to income, cumulative risk, and adjustment in 306 preschool-age children from families representing a range of income.
Lengua, L. J., Moran, L. R., Zalewski, M, Ruberry, E, Kiff, C & Thompson, S. (2015). Relations of Growth in Effortful Control to Family Income, Cumulative Risk, and Adjustment in Preschool-age Children. Journal of Abnormal Child Psychology. dx.doi.org/10.1007/s10802-014-9941-2Lengua Et Al 2015