I have always been fascinated with the idea of personality differences, similarities and influences among siblings. My interest in the topic most likely stemmed from being a twin and observing over the last 20 years the personalities of both myself and my twin brother, Luke. Although we grew up in the same house, the external influences surrounding us were almost entirely different- from the people we spent time with to the activities we enjoyed in our free time. Observing the contrasting qualities between my brother and myself, my belief in the value of "nonshared environmental factors" was reassured and got me thinking about other personality influences in effect.
In addition to focusing solely on external influences, I have always been intrigued by the role of birth order and its impact on personality. My brother Luke and I seem to represent opposite sides of the personality spectrum and our older sister Ashley, maybe even a completely different third part. Although my siblings and I all get along very well, our personalities, attitudes and beliefs are very different from one another.
When reading through the idea of "birth order" mentioned in the book, the authors cited the idea that "firstborns tend toward achievement, middle-borns toward diplomacy, and later-borns toward risk taking". Although the book could not prove the extent that these generalizations were true, the personality assignments almost directly match the distinctions with my siblings and I.
This being said, I would be interested to see how birth order is affected by the birth twins (both fraternal and identical). Does birth order still apply if two individuals are born only minutes apart? And in the case of my brother and I, could only a 60 second difference really create an "order" affecting our personalities?