Understanding Birth Order: A Within-Family Analysis of Birth Order Effects

A Adler, often thought of as the father of birth order research, claimed that birth order can have lasting effects on one’s personality. He stated that birth order differences in personality are mostly due to siblings trying to compete for the attention of their parents by claiming certain niches or roles within the family (Adler, 1964). One theory underlying this need to establish a role is the social comparison theory (Festinger, 1954). This theory states that humans have a basic need to evaluate themselves and that the easiest way to do so is to compare themselves to others. Within a family, individuals compare themselves to their siblings in order to decide what role they are going to play. If the first-born is extremely intelligent and a subsequent sibling believes that they will not be able to achieve that level of intelligence, they will find another role to play, such as the most sociable child or the most creative one, in order to earn their parents’ attention. At first glance, birth order effects are solely dependent on whether the child was the first-born, middle born, or last-born; in reality, there are many other variables that play into the personality differences seen with respect to birth order (Healy & Ellis, 2007). Examples include age, socioeconomic status of the parents, education of the parents, family size, and gender. Many previous studies that show support for birth order effects have failed to control for these important variables (Kurtz, 2011). For example, some studies fail to control for family size by comparing the personality effects of birth order within a two-child family with those of a six-child family, thus observing differences that might not truly be due to birth order (Ernst & Angst, 1983). Similarly, Rohde et. al. (2003) found that mother’s age is an important moderating variable in birth order that is often not controlled for. Due to the lack of control in these studies, birth order effects are still highly debated today. This study examines classic birth order effects on the following variables: intelligence, openness to experience, conscientiousness, extraversion, agreeableness, neuroticism, impulsivity, sense of selfconcept and self-control, and gender attitudes, which could be indicative of a more traditional viewpoint. It also tests to see if the gender composition of a sibling group influences birth order effects. For the purposes of this study, the following classic birth order characteristics will be referenced and challenged: First-borns are often thought to be high-achieving, responsible, conservative, competitive, and organized. As the first-born, they grow up for a period of time with all of their parents’ attention. When a second child is born, that attention is taken away from the first-born, making them feel “dethroned” and consequently crave attention (Adler, 1964). Furthermore, the first-born is thought to have the highest level of intelligence, score highest on tests of extraversion, and respect authority the most. This is likely due to their search for power, their perceived duty to set an example for younger siblings, and a desire to please their parents (Adams, 1972; Kirkcaldy, Furnham, & Siefen, 2009; Zajonc, 2001). The middle child is sometimes considered the “lost child” because they are neither the highest achieving, nor the favored baby of the family, making them feel like they do not belong (Eckstein, 1978; Healey, & Ellis, 2007; Paulhus, Trapnell, & Chen, 1998). They are likely to have the fewest “acting out” problems (Searcy, Cowen, & Terell, 1977) and are more sociable because they rely on friends instead of family for attention (Salmon, 2003).