Final answer:
A researcher interested in the evolution of parent-child relationships across different life stages would be classified as a developmental psychologist. This area of psychology examines changes in emotional, cognitive, and relational aspects throughout one's life. Researchers use methods like longitudinal studies, naturalistic observations, and review existing theories like Baumrind's parenting styles to understand these developments.
Step-by-step explanation:
A researcher interested in how parent-child relationships change as parents and children get older would most likely be a developmental psychologist. Developmental psychology focuses on the systematic changes that occur throughout a person's life, including socioemotional, cognitive, and physiological development. When examining the dynamics of parent-child relationships across different stages of life, a developmental psychologist may utilize a variety of methods such as longitudinal studies, naturalistic observations, or case studies to gather insights.
For example, Diana Baumrind's research into parenting styles like authoritative, authoritarian, permissive, and uninvolved parenting has been influential in understanding how these styles impact a child's socioemotional growth. Additionally, research into attachment, such as the work done on understanding how secure and insecure attachments between parents and infants develop, falls under the purview of developmental psychology.
Furthermore, as shown by the research on lifespan development, including the works of Sigmund Freud on psychosexual development during childhood and Abraham Maslow on personality, developmental psychology also addresses how interactions and relationships evolve as individuals age, contributing to the overall understanding of human development.