The article by Mary Klevjord Rothbart, published in *Child Development* in 1981, describes the development and validation of a caretaker-report instrument for assessing infant temperament. The study aimed to create a psychometrically adequate instrument that could measure various aspects of infant reactivity and self-regulation, including activity level, soothability, fear, distress to limitations, smiling and laughter, and duration of orienting. The instrument was based on the work of Thomas, Chess, and others, with additional influences from animal behavior genetics and longitudinal studies of personality. The research involved a longitudinal analysis of 463 Infant Behavior Questionnaires completed by parents of infants at 3-, 6-, 9-, and 12-month intervals. Conceptual and item analyses were conducted to ensure that the scales were conceptually distinct and had adequate psychometric properties. The scales were found to have high internal reliability, and the study reported stability in activity level and smiling and laughter scales from 3 to 12 months, while duration of orienting and soothability showed less stability. Fear and distress to limitations showed stability only beyond 6 months. The article also discusses the limitations of parent-report measures, such as the influence of the home environment on observed behavior, and the potential for response biases. The findings suggest that temperament measures can provide valuable insights into individual differences in infant behavior and may help trace the relationship between early characteristics and later social and cognitive development.The article by Mary Klevjord Rothbart, published in *Child Development* in 1981, describes the development and validation of a caretaker-report instrument for assessing infant temperament. The study aimed to create a psychometrically adequate instrument that could measure various aspects of infant reactivity and self-regulation, including activity level, soothability, fear, distress to limitations, smiling and laughter, and duration of orienting. The instrument was based on the work of Thomas, Chess, and others, with additional influences from animal behavior genetics and longitudinal studies of personality. The research involved a longitudinal analysis of 463 Infant Behavior Questionnaires completed by parents of infants at 3-, 6-, 9-, and 12-month intervals. Conceptual and item analyses were conducted to ensure that the scales were conceptually distinct and had adequate psychometric properties. The scales were found to have high internal reliability, and the study reported stability in activity level and smiling and laughter scales from 3 to 12 months, while duration of orienting and soothability showed less stability. Fear and distress to limitations showed stability only beyond 6 months. The article also discusses the limitations of parent-report measures, such as the influence of the home environment on observed behavior, and the potential for response biases. The findings suggest that temperament measures can provide valuable insights into individual differences in infant behavior and may help trace the relationship between early characteristics and later social and cognitive development.