Birth Order

Adlerian psychology and contributions from developmental psychology and role theory suggest that personality variables may relate more meaningfully to the roles that siblings construct or are ascribed rather than to actual birth order (Adler 1927; Hoffman 1991). That is, although a child may be the youngest, the gender mix of the siblings, the differences in ages, and other unique variables may combine to create a firstborn role for the youngest child.

Studies that have measured the perceived or psychological birth order of young adults revealed that 45 percent of men and 52 percent of women have a distinctive sibling role in their families and that psychological and actual birth order is in agreement for 19 percent of people (Campbell, White, and Stewart 1991; Stewart and Campbell 1998). Further, sibling roles may mediate the effects of actual birth order and family atmosphere on personality traits (Stewart, Stewart, and Campbell 2001). Consequently, research using sibling or family roles may be more revealing than studies relying upon actual birth order, especially those that simply split participant samples into firstborn versus laterborn; this may mask the important effects of the nonshared family environment.