Final answer:
According to Adler's theory, the first-born child is most likely to develop at a remarkably fast rate due to compensatory overachievement. However, research has not definitively supported Adler's birth order hypotheses as personality development is influenced by various factors.
Step-by-step explanation:
In the context of Adler's idea of birth order and its impact on personality development, the child most likely to develop at a remarkably fast rate is the first-born. According to Adler, first-born children may turn into overachievers as a way to compensate for losing their parents' undivided attention when a sibling arrives. Conversely, later-born children, including middle children and last-born, develop different personality traits, often influenced by their efforts to differentiate themselves from their siblings. The only child, with constant parental attention and no siblings to compete with, may also develop unique personality characteristics.
It is important to note that, despite Adler's theories receiving considerable attention, subsequent research has not definitively supported his claims regarding birth order. Personality development is a complex process influenced by a wide range of environmental, genetic, and social factors, and birth order is just one element that may contribute to this development.