Significant relationships (which were largely found to be independent effects) were found between most of the factors measured as follows:

Jealousy and Attachment
Secure individuals were significantly less jealous (across all three types of jealousy examined) than insecure individuals, of whom the anxious subjects consistently experienced higher levels of jealousy.

Jealousy and Birth Order
Laterborn participants scored significantly higher on all three measures of jealousy than firstborn participants.

Jealousy and Personality
The personality attributes of neuroticism, social anxiety, rigidity, hostility and low self esteem were significantly related to jealousy.

Personality and Attachment
Compared to insecure participants, secure attachment correlated positively with dominance and self-esteem, and negatively with hostility, rigidity, social anxiety and neuroticism. Participants with avoidant attachment style were differentiated from those who were anxious by scoring lower on neuroticism and dominance.

Personality and Birth Order
The only significant personality difference found was that firstborn children scored higher in egoism.

Attachment and Birth Order
No significant relationships were found between attachment and birth order.

Relationship Variables and Birth Order
Firstborns were found to be more likely to engage in sex outside of existing relationships than laterborn subjects.

The authors note that birth order research has generally produced inconsistent results but go on to suggest that the increased levels of jealousy experienced by laterborn subjects may be due to their having always had to compete with siblings for parental attention, whereas firstborn subjects will have experienced at least a short period of exclusive attention. This concorded with a secondary result that subjects who were only children (who would never have experienced competition with siblings) appeared to experience even less jealousy than firstborns.