Mary K. Rothbart views temperament as the individual personality differences in infants and young children that are present prior to the development of higher cognitive and social aspects of personality. Rothbart further defines temperament as individual differences in reactivity and self-regulation that manifest in the domains of emotion, activity and attention. Moving away from classifying infants into categories, Mary Rothbart identified three underlying dimensions of temperament. Using factor analysis on data from 3 -12 month old children, three broad factors emerged and were labelled surgency/extraversion, negative affect, and effortful control.