They found temperament in infancy predicted later development in some respect.
Step-by-step explanation:
Different psychologists put forwarded their views about child psychology and development where their age wise classification has been done. From infancy to adulthood there are four distinct stages: infant, childhood, adolescence and adulthood. Each of the category has their own distinctive features.
In infancy and childhood they found temperament, immaturity whereas with the passage of time during adulthood they become matured enough. Mental development creates a behavioral and mental map in child's life. After their classification in 21st century several others gave their views about child psychology.