Maddie Rauzi and Dylan Antovich

1. Birth order, conscientiousness, and openness to experience:Tests of family-niche model of personality using a within-family methodology Maddie Rauzi and Dylan Antovich

2. Introduction: Salloway’s Theory • Ernst & Angst (1983) – No birth order effects on personality when socioeconomic status and family size are taken into account. • Salloway(1996, 2001) challenged their conclusion and offered a new perspective. Sibling competition leads children to cultivate niches with the family. • Firstborns = receive more investment from parents and aim to fulfill parents’ expectations. • more conscientious, responsible, ambitious, organized, academically successful, traditional and conservative, and more likely to endorse conventional mortality. • Laterborns = try and find a niche not already filled by older siblings, and face domination/bullying by older siblings. • identify less with parents, more open to experience, more likely to emphasize with downtrodden, be supportive of egalitarian social change, question the status quo, and to resist authority and conformity.

3. Author’s points: 1) Salloway’s theory concerns differences WITHIN families. • Disparities between SIBLINGS lead siblings to adopt different strategies for receiving parental investment. • Within-family research designs (asking siblings to rate each other) yield significant birth order effects, unlike between-family designs. 2) Competition between siblings promotes differentiation in order to alleviate conflict, and thus siblings farther apart in age will be less different. • Strongest birth order differences in siblings 2- 5 years in age, and between siblings who are ordinally closer • “functional birth order” is important, blending/changing of the family creates too many confounds. • Differences between firstborn and secondborn brothers more pronounced than firstborn and secondborn sisters [ H Y antigen ].

4. Hypothesis: • Firstborns are more Conscientious (eg responsible, organized, and academically achieving) • Laterborns are more Open to Experience (rebellious, unconventional, and liberal)

5. Study 1: Methods • Second-year Personality Psychology students! • Listed all siblings in order of birth, provided their siblings’ ages, sex, relationship to respondent, and coresidence status. • Rank ordered their siblings on six personality traits: “rebellious”, “noncomformist”, “open to new experience”, “responsible/organized”, “scholastically achieving”, and “liberal”. • Of 209 questionnaires, 161 were used. • Avg firstborn = 25.6 years and avg secondborn= 23 years.

6. Study 1: Results • Hypothesis supported! • However, bigger effect between female-female siblings compared to male-male siblings.

7. Study 2: Birth order effects in an older sample 1st study had one major criticism: Use of university aged population (college student = high achieving, goal oriented, high school sibling = angsty, rebellious teen) To control for this, the second study was sent (by mail) to an older population (the New Zealand Coast-to-Coast Endurance racers)

8. Study 2: Methods • Questionnaires mailed to 750 participants: • Same questionnaire format used, but with different items: Rebellious, lazy, nonconformist, open to new experiences, responsible/organized, conventional, scholastically achieving and liberal • 237 were returned • 174 were completed correctly • First born and second born had to be 1.5 to 5 years apart • Siblings had to be raised together w/out intervening step or half siblings • Average age of firstborns was 37.5

9. Study 2: Results The adjectives from the survey were assigned to two categories, as with the first study: • Openness to Experience defined as: Rebellious, open to new experience, liberal, nonconformist, and conventional (reverse coded) • Conscientiousness defined as: Lazy (reverse coded), responsible/organized, and scholastically achieving The adjectives within each group were correlated by r> .30

10. Study 2: Results cont. Predictions from Sulloway’s theory were confirmed • Firstborns scored significant lower on openness to experience (p = .002) • Secondborns scored lower on conscientiousness (p = .04)

11. Study 2: Results cont. • In order to test Beer and Horn’s prediction (hypermasculinization of male firstborns) they also separated male-male and female-female sibling pairs • The effect predicted by this theory did not hold true • Effect size for female-female were larger than male-male

12. General Discussion: • This study was effective at: • ensuring within-family comparisons were made • ensuring that only full siblings were compared • ensuring that siblings were raised in the same family • This had not been met in previous studies, leading to environmental confounds • Both studies found effects as predicted, but the first study showed greater disparity in Openness to Experience

13. General discussion cont. • The evolutionary perspective: • This data supports the family-niche theory of personality, in which offspring must behave differently too compete for parental resources • This mechanism shapes the individual fitness of the offspring, permanently altering behavior patterns, creating personality

14. Questions we have about this study: • These data are self-report (and more importantly, reporting for subjective opinions of siblings)… sibling rivalry? • There is no explanation about how being rebellious from parents would improve fitness from resource competition… how is it beneficial? • How do OTHER siblings fare under the birth-order assumption of personality – separate mechanism? • Can we conclude much about “Personality” based on the measure of one trait – “Conscientiousness/Openness to Experience”? • What about twins? Do they compete? (*cough* Laura and Kyle)