RESUMEN
OBJECTIVE: The current study compares the development of negative and positive emotionality of irritable and nonirritable neonates. BACKGROUND: Research indicates that the first few months of life are marked by decreases in negative emotionality and increases in positive emotionality. METHODS: The Neonatal Behavioural Assessment Scale (NBAS) was administered twice to 111 neonates at 3 and 4 weeks of age to select a sample of irritable neonates and a comparison group of nonirritable neonates. Mothers completed assessments of negative and positive emotionality at 1, 2, 4, and 9 months of age. RESULTS: Both irritable and nonirritable neonates demonstrate a significant decrease in frustration and a significant increase in positive emotionality from 2 to 4 months of age. Irritable neonates also demonstrate a significant decrease in negative emotionality from 4 to 9 months of age. Both irritable and nonirritable neonates demonstrate considerable stability in negative and positive emotionality. CONCLUSION: Implications of these results for parent education and early intervention are discussed.