Birth Order Position and Prosocial Tendencies

This study investigated the relationship between psychological birth order position and different types and levels of prosocial tendencies. An ex postfacto, between-family research design was used. Data on prosocial tendencies were obtained from 888 college students (females = 80.4%, mean age = 20.94 yrs, SD = 2.83; males = 19.6%, mean age = 21.62 yrs, SD = 2.44). Participants completed a biographical questionnaire as well as the Prosocial Tendencies Measure (Carlo & Randall, 2002). Data were analysed to compare and contrast prosocial tendencies between demographics using parametric ANOVAs, t tests and the Mann-Whitney Test. Significant differences in prosocial tendency scores were only found between middle-borns and last-borns on altruism, with middle-borns scoring significantly higher in prosocial tendencies than last-borns. There is no evidence to suggest that a definitive link between prosocial tendencies and birth order exists in this study.     

Context-Specific Learning, Personality, and Birth Order

Most people believe that learning to get along (or not get along) with their siblings played an important role in shaping their personality, and that their position in the family—oldest, youngest, or in the middle—had lasting effects. Yet studies of birth order generally fail to support these beliefs. The apparent contradiction can be resolved by taking into account the context-specific nature of learned behavior. There is abundant evidence that people do not automatically transfer behavior from one context to another: They wait until they have evidence that what they learned in Context 1 will also be useful in Context 2. Because patterns of behavior acquired in the family of origin tend to be useless or inappropriate in other settings, birth order effects show up only in that context. Outside the family they grew up in, firstborns and later-borns are indistinguishable in personality.     

Birth Order Effects and Rebelliousness: Political Activism and Involvement with Marijuana

Frank Sulloway (1996) has claimed that later-borns are more likely to rebel against the status quo than are firstborns. The two studies reported here attempt to examine more fully Sulloway's claims about rebelliousness. The studies draw on archival data from studies of high school and college students in a midwestern state between 1969 and 1982. The current studies compare the effects of birth order, gender, family size, and father's education on two self-report measures: participation in protests and demonstrations, and involvement with marijuana. The data on involvement with marijuana provided support for Sulloway's thesis that later-borns are more rebellious than firstborns, but the data on participation in protests and demonstrations did not. These mixed findings, which contribute to the ongoing debate about Sulloway's theory, are discussed.