Dr. Hertzig's past research has focused on the elucidation of both normal and aberrant developmental processes. Together with colleagues (Alexander Thomas, MD, Stella Chess, MD, and Herbert Birch, MD, PhD) she examined the longitudional course of individual differences in temperamental organization in healthy middle and upper middle class children. These investigations were further expanded to include studies of children who derived from other socioenomic backgrounds, (Puerto Rican working class) as well as those who had been exposed to conditions which placed them at risk of damage to the central nervous system (low-birth weight). Together with Herbert Birch, MD PhD, Steven Richardson, PhD and Jack Tizard, PhD, she examined the impact of other potential insults to the developing nervous system (severe malnutrition during the first two years of life) on cognitive and behavioral development. As an extension of these interest she designed a schedule for the assessment of non-focal neurologic signs, described their stability over time, as well as their association with emotional, behavioral, and learning difficulties in children and adolescents. Additional areas of investigation have included studies of both the biology and psychology of children, adolescents and adults with Pervasive Developmental Disorder. With Anne McBride, MD, Dr. Hertzig has studied aspects of serotonin metabolism in the pervasive and other developmental disorders. Other studies have focused on aspects of social and emotional functioning in autistic persons including the expression of affect and the ability of autistic persons to utilize affective information in the solution of cognitive problems.