THE EFFECT OF BIRTH ORDER ON PERSONALITY

The effect of Birth Order on Personality

Abstract

The Alders' Birth Order Model (Alders, 1996) suggests that an individual's birth order acting as a proxy for within-family environmental factors like age, size and strength relative to ones siblings influences the strategies used to gain resources and minimize sibling conflict. Recent within-family birth order research (for example Paulhus, Trapnell and Chen, 1999; Healey & Ellis, 2007) has found a systematic effect of birth order on personality, with firstborn siblings found to be more conscientious and secondborn siblings more open to experience. However, an examination of birth-order effects by independent raters, has been lacking in the birth order literature. Furthermore no prior examination comparing the type of stimulus material used to elicit participant responses has been conducted. Study 1 (N = 203) sought to replicate previous birth order findings for the two Big-5 traits Conscientiousness and Openness to Experience, while also testing an alternative explanation (hypo-masculinization hypothesis) for observed birth-order differences (Beer & Horn, 2000). Study 2 compared the efficacy of four different types of stimulus material (rankings, ratings, independent ratings and real-world scenarios) in observing birth order effects (combined N = 544), while also testing novel predictions about the saliency and generalis ability of birth-order effects on personality outside the context of the family. General support was found for the Alders' Birth Order Model across studies and across stimulus materials, but limited support was found for the nature of within family personality differences between siblings extending to contexts outside the family environment.

Table of Contents

CHAPTER I: INTRODUCTION4

Nature of Study4

Problem Statement6

Research Questions10

Application of Results10

Overview of Current Research Aims14

Theoretical Framework17

A Brief History of Birth Order Research17

Alders and the Evolutionary Niche Model of Personality21

SUMMARY OF RESEARCH ARTICLES26

CHAPTER II: LITERATURE REVIEW32

Alders' Birth Order Model32

Extended Alders' Birth Order Model34

Hyypo-masculinization Hypothesis35

Hypotheses36

CHAPTER III: METHODOLOGY39

Study 139

Participants and Procedure39

Measures40

Data analysis42

Study 242

Participants42

Measures44

Procedure46

CHAPTER IV: RESULTS48

Composite Construction48

Personality Differences by Birth Order49

Gender and Family Size analyses of "nonconformity"51

Analysis of PHH52

Study 253

Ranking Data: r Born vs 2nd Born Composite Variables54

Composite Variable Construction54

Personality Differences by Birth Order: Ranking Data55

Rating Data: I" Born vs 2nd Born Composite Variables57

Composite Variable Construction57

Reliability Checks for Composite Construction58

Pre-Analysis Data Source Inter-correlations for Rating Data59

Personality Differences by Birth Order: Rating Data60

Court case Scenarios: I" Born vs 2nd Born62

Rating Data: I" Born vs 2nd Born Conformity/Nonconformity64

Interaction Effects: Birth Order, Gender and Family Size65

Conscientiousness65

Strength of Effect of Birth Order, Gender and Family Size69

Peer-ratings of Sibling Personality70

Personality Differences by Birth Order71

CHAPTER V: DISCUSSION73

Extended Alders' Birth Order: Gender, Family Size and Conformity76

Hypo-masculinization hypothesis (PHH)77

Limitations and Implications for Future Research78

Personality Differences by Birth Order: Ranking and Rating Data Only80

Personality Differences by Birth Order: Court case summaries83

Personality Differences by Birth Order: Conformity84

Personality Differences by Birth Order: Peer Ratings84

Summary85

CHAPTER VI: CONCLUSION87

Methodological Issues93

Limitations and Caveats95

REFERENCES97

APPENDIX102

ARTICLES126

The effect of Birth Order on Personality

Chapter I: Introduction

The overarching tenant of this dissertation is that the birth order of individuals within a family implies differing developmental needs. As a means to ensure access to the resources determined by these needs, siblings diverge in their developmental strategies by "carving their own niche" and ...