" Older and stronger firstborns dominate their younger brothers and sisters and thus tend to like the world the way it is. The siblings who follow have a harder time competing with the firstborn and consequently rebel against the status quo, developing a “revolutionary personality.” Firstborns are also more introverted and inflexible since they need less support. By contrast, laterborns are more extroverted and agreeable since they need assistance from others to compete with firstborns. "

― David Lockwood