There are many theories about how an individual's personality develops or how different characteristics and traits are formed in people. Psychiatrist Alfred Adler was the first to suggest that the order in which a person is born had a profound effect on the development of his or her personality. He called his idea the birth order theory. Adler's work on this theory covers the eldest child, commonly referred to as the firstborn, as well as the middle, youngest, and only child. Work by other experts in the field has expanded his theory to include twins (twins, triplets, etc.), half-siblings, siblings with disabilities, and siblings with more than a five-year gap. So, according to Birth Order Theory, how does a person's birth order contribute to their personality, and what are the commonly shared characteristics in each birth position? Are there other factors that may contribute to or influence an individual's personality development in relation to birth order theory that need to be considered? If so, how accurate is the theory really? I will try to answer these questions. Firstborn According to Adler the firstborn is usually a caring and polite individual because he most likely grew up helping his parents take care of their younger siblings. For the same reason, firstborns are more likely to be well-organized and more responsible than younger siblings. It makes sense that there are no other children around when their parents give birth to them, firstborns are used to receiving their undivided attention and affection before the arrival of their siblings, and if their parents have not prepared them for the The arrival of a new brother or sister can have a negative effect on the firstborn, making... middle of paper... reversals that call into question the validity of this assumption. She believes it is more important to recognize the fact that twins and other groups try to find ways to distinguish themselves from each other (p. 124). Twins' siblings are also worth mentioning because they tend to feel left out – neither special nor important. This can lead to feelings of low self-esteem or feeling pressured to overachieve in an attempt to get the attention and praise they need and feel like they deserve but have not achieved (Blair, 2011, p.126). Works CitedAnsbacher, H., & Ansbacher, R. (Eds.). (1956). The individual psychology of Alfred Adler: a systematic presentation in selections from his writings. (1st ed.). New York, NY: BasicBooks, Inc. Blair, L. (2011). Birth Order: What Your Position in the Family Really Tells You About Your Character. London, UK: Piatkus.