Statistically, only children perform higher on achievement tests than their age-mates with siblings. (Keller and Zach, 2002; Phillips, Long, and Bedeian, 1990; Roberts and Blanton, 2001; Rosenberg and Hyde, 1992; Smith 2004) This is typically attributed to the amount and quality of parental investment throughout the child's life. A pressure to please the parents by succeeding exists, often driving the child to fulfill expected goals. Academic superiority occurs in only children in other cultures. Since China enacted the one-child policy in 1979, many studies have been conducted to analyze the repercussions. Post and Falbo's 2000 study found the following:
In terms of academic achievement, urban only children were found to outperform their later-born peers, even after parental characteristics, gender, and nursery school attendance were controlled for. (p. 370)
Singletons and firstborns are the most overrepresented birth order positions in politics. According to a reference in a study by Andeweg and Van Den Berg, (2003) this fact applies to U.S. presidents, congress, and state governors, British and Australian Prime Ministers, and all offices of the Netherlands' government as well as other countries. This cross-culture achievement and leadership of singletons has a multitude of empirically supported data to conclude that only children, in fact, have a consistent advantage over other birth order positions, especially laterborn children with multiple older siblings. (Roberts and Blanton, 2001)
Intelligence and the ability to achieve certainly give adult only children an advantage in the workplace, collegiate life, and in other adult arenas. However, this expectation to reach high achievement levels can lead to Type A personality tendencies and unhealthy perfectionism. Firstborn and only children statistically score higher on the California Psychological Inventory (CPI), which is used to assess Type A status. Men statistically score higher than women do. The higher the score on the CPI, the more Type A tendencies and behavioral patterns a person possesses. Individuals exhibiting Type A tendencies are coronary-prone, hard driving, competitive, driven by achievement and obsessed with accomplishing more in less time. (Phillips, Long, and Bedeian, 1990) Similarly, singletons exhibit perfectionism of all levels, much like many types of onlies exist. No significant data exists to link a particular type of perfectionism to singletons, however those exhibiting Type A tendencies would likely exhibit maladaptive perfectionism, which causes a person to attempt to accomplish unrealistic expectations or achievements. (Ashby, LoCicero, and Kenny, 2003) Healthy perfectionism does exists and well-adjusted singletons exercise their intellectual superiority to achieve their realistic goals and aspirations in a healthy manner.