The study of personality has many facets. There are many factors that shape a person's personality and many definitions of the word itself. Personality has the ability to intensely influence one's interpersonal relationships in many respects. One personality factor that has been studied extensively is birth order. Birth order refers to a person's numerical position in the birth order in his or her family and how that person fits into the family constellation (Ernst & Angst, 9). It has been observed in many studies that members of each rank – the oldest, the middle, the youngest, or single children – tend to have personalities similar to those of members of the same rank (Ernst & Angst, 13-16). It can be assumed that birth order will have an effect on all aspects of life, especially interpersonal relationships. There have been many studies that have focused on birth order, but the results have been inconclusive. Ernst and Angst (26) conducted more than 1,000 birth order studies between 1946 and 1980 with no statistically significant correlation between birth order and personality traits. This may be attributed to the near impossibility of controlling for other variables in the study, such as parenting techniques, economic status, and the parents' life stages during which they raise their children (Travis & Kohli, 501-502). Alfred Adler was the first researcher to recognize birth order as a noteworthy factor in personality development. Adler understood that “even though children have the same parents and grow up in almost the same family context, they do not have identical social environments” (Hjelle & Ziegler, 192). Adler was also the first to describe personality differences between siblings. The older child tends to be with...... middle of paper ......psychology: Journal of Adlerian Theory, Research & Practice, 48(1), 109-118.Hjelle, Larry A. & Ziegler , Daniel J. (1992). Personality theories: basic assumptions, research and applications. New York: McGraw-Hill, Inc, 195-207. Leman, Kevin. (2000). The New Book of Birth Orders: Why You Are the Way You Are. Minnesota: Baker Book House Company, 155-267.Todd, Judith, Friedman, Ariella and Steele, Sharon. (1993). Birth order and sex of siblings Effects on self-evaluations of interpersonal power: Gender and ethnic differences. Individual Psychology: Journal of Adlerian Theory, Research & Practice, 49(1), 86-93.Toman, Walter. (1961). Family constellation. New York: Springer Publishing Company, 334-461. Travis, R., & Kohli, V. (1995). The birth order factor: ordinal position, social strata and educational achievement. The Journal of Social Psychology, 135, 499-507.