BIRT H ORDER A N D RELATI ONSHIP S Family, Friends, and Sexual Partners Catherine Salmon Simon Fraser University Previous studies (Salmon 1999; Salmon and Daly 1998) have found that sex and birth order are strong predictors of familial sentiments. Middle- borns tend to be less family-oriented than firstborns or lastborns, while sex differences seem to focus on the utility of kin in certain domains. If this is a reflection of middleborns receiving a lesser degree of support from kin (particularly in terms of parental investment), are middleborns turning to reciprocal alliances outside the family, becoming friendship specialists? Are there comparable birth order differences with respect to mating strategies? In this study, the impact of birth order on attitudes to- ward family, friends, and mating were examined. Two hundred and forty- five undergraduates completed a questionnaire relating to their attitudes toward friends and family as well as some aspects of mating behavior. Birth order did have a significant impact in several areas. Middleborns ex- pressed more positive views toward friends and less positive opinions of family in general. They were less inclined to help family in need than firstborns or lastborns. Mating strategies also appeared to be influenced by birth order, most notably in the area of infidelity, with middleborns being the least likely birth order to cheat on a sexual partner. ~YWORDS: Attitudes; Birth order; Helping; Parental investment; Sociosexuality Received May 29, 2002; accepted September 30, 2002. Address all correspondence to Catherine Salmon, Psychology Department, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, V5A 1S6, Canada. Email: [email protected]Copyright 2003 by Walter de Gruyter, Inc., New York Human N ature, V ol. 14, No. 1, pp. 73--88. 1045-6767/03/$1.00+.10 7 3
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P r e v i o u s s t u d i e s ( S a l m o n 1 9 9 9 ; S a l m o n a n d D a l y 1 9 9 8 ) h a v e f o u n d t h a ts e x a n d b i r t h o r d e r a r e s tr o n g p r e d i c t o r s o f f a m i l i a l s e n t i m e n t s . M i d d l e -
b o r n s t e n d t o b e l e s s f a m i l y - o r i e n t e d t h a n f i r s t b o r n s o r l a s t b o r n s , w h i l e
s e x d i f f e r e n c e s s e e m t o fo c u s o n t h e u t i l i ty o f k i n i n c e r t a in d o m a i n s . I f
t h i s i s a r e f l e c t i o n o f m i d d l e b o r n s r e c e i v i n g a l e s s e r d e g r e e o f s u p p o r t
f r o m k i n ( p a r t ic u l a r l y i n t e r m s o f p a r e n t a l i n v e s t m e n t ) , ar e m i d d l e b o r n s
t u r n i n g t o r e c ip r o c a l a ll ia n c e s o u t s i d e t h e f a m i ly , b e c o m i n g f r i e n d s h i p
s p e c i a li s ts ? A r e t h e r e c o m p a r a b l e b i r t h o r d e r d i f f e r e n c e s w i t h r e s p e c t t o
m a t i n g s t r at e g i es ? I n t h i s s t u d y , t h e i m p a c t o f b i r t h o r d e r o n a t t it u d e s t o -
w a r d f a m il y , f r ie n d s , a n d m a t i n g w e r e e x a m i n e d . T w o h u n d r e d a n d f o rt y -
f iv e u n d e r g r a d u a t e s c o m p l e t e d a q u e s t i o n n a i r e r e l a ti n g t o th e i r a tt i tu d e st o w a r d f r ie n d s a n d f a m i l y a s w e l l a s s o m e a s p e c t s o f m a t i n g b e h a v i o r .
B i r th o r d e r d i d h a v e a s i g n if i c an t i m p a c t i n s e v e r a l ar e a s. M i d d l e b o r n s e x -
p r e s s e d m o r e p o s i t iv e v i e w s t o w a r d f r ie n d s a n d l es s p o s i t i v e o p i n i o n s o f
f a m i l y i n g e n e ra l . T h e y w e r e l es s in c l i n e d t o h e l p f a m i l y i n n e e d t h a n
f i rs t b o r n s o r l a s t b o r n s . M a t i n g s t r a t e g i e s a ls o a p p e a r e d t o b e i n f lu e n c e d
b y b i r t h o r d e r , m o s t n o t a b l y i n t h e a r e a o f i n f i d e l i t y , w i t h m i d d l e b o r n s
b e i n g t h e l e a s t l i k e l y b i r t h o r d e r t o c h e a t o n a s e x u a l p a r t n e r .
~ Y W O R D S: A t t i t u d e s ; B i r t h o r d e r ; H e l p i n g ; P a r e n t a l i n v e s t m e n t ;
S o c i o s e x u a l i t y
R e c e i v e d M a y 2 9 , 2 00 2; a c c e p t e d S e p t e m b e r 3 0 , 2 00 2.
Ad dress al l correspondence to Cather ine Salmon, Psychology Department , Sim on Fraser
Univers ity , 8888 U nivers i ty D rive , Burnaby, Br i tish Columbia, V 5A 1S6, Canada. Email:
7 4 H u m an N a t u re , V o l. 1 4, N o . 1 , 2 0 03
T h e o r e t ic a l m o d e l s o f th e e v o l u t i o n o f p a r e n t a l i n c l in a t i o n s p r e d i c t t h a t
p a r e n t s w i l l o f t e n tr e a t t h e i r o f f s p r i n g d if f er e n ti a ll y . T h e r e a r e g r o u n d s f o r
p r e d i c t i n g d i s c r i m i n a t i v e p a r e n t a l s o l i c i t u d e i n r e l a t i o n t o a n u m b e r o f
v a r ia b l e s , i n c l u d i n g o f f s p r i n g a g e , p a r e n t a l a g e , b i r th o r d e r , o f f s p r in g s e x ,
a n d c u e s o f p a r e n t a g e ( C l u t t o n - B r o c k 1 99 1; D a l y a n d W i l s o n 1 99 5; T r i v e r s
1 97 4; T r i v e rs a n d W i ll a r d 1 97 3). T h e u n i f y i n g n o t i o n b e h i n d t h e s e t h e o r i e s
is t h a t n a t u r a l s e l e ct io n h a s s h a p e d p a r e n t a l p s y c h o l o g i e s t o fu n c t i o n a s i f
t h e y " v a l u e " i n d i v i d u a l o f f sp r i n g a n d i n v e s t m e n t s in th e i r d e v e l o p m e n t
i n p r o p o r t i o n t o t h e e x p e c t e d i m p a c t s o f s u c h i n v e s t m e n t s o n p a r e n t a l f i t-
n e s s ( g e n e ti c p o s t e r i ty ) i n a n c e s tr a l e n v i r o n m e n t s . T h e f o c u s o f t h is p a p e r
is o n t h e i m p a c t o f b i r t h o r d e r n o t o n l y o n f am i l i al s e n t im e n t , b u t o n n o n -
k i n re c i p r o c a l r e l a t io n s h i p s ( f r i e n d s a n d s e x u a l p a r t n e r s ) .
T h e r e a r e s e v e r a l t h e o r e t ic a l a n d e m p i r ic a l r e a s o n s f o r e x p e c t i n g b i r th
o r d e r t o p l a y a r o l e i n p a r e n t a l i n v e s t m e n t . T h e a n t i c i p a t e d r e l e v a n c e o f
b i r t h o r d e r i s, i n p a r t , a c o r o l l a r y o f t h e r e l e v a n c e o f o f f s p r i n g a g e . O n e ' s
e x p e c t e d c o n t r i b u t i o n t o p a r e n t a l f i t n e s s r e s i d e s m a i n l y i n o n e ' s r e p r o -
d u c t i v e v a l u e ( e x p e c t e d f u t u r e r e p r o d u c t i o n ) a n d t h i s q u a n t i t y i n c r e a s e s
w i t h a g e u n t i l a t l ea s t p u b e r ty , m a k i n g a n o l d e r i m m a t u r e o f f s p ri n g m o r e
v a l u a b l e f r o m t h e p a r e n t a l p e r s p e c t iv e t h a n a y o u n g e r o n e . T h i s b e c o m e s
a p p a r e n t, i n h u m a n s , w h e n t o u g h c h o ic e s h a v e t o b e m a d e . W h e n o n e
c h i l d m u s t d i e s o o t h e r s c a n s u r v i v e , i t i s a p p a r e n t l y a c r o s s -c u l tu r a l u n i -
v e r s a l t h a t t h e y o u n g e s t is th e l i k e li e s t v i c t i m ( D a l y a n d W i l so n 1 98 4). F o r
t h e s e r e a s o n s , S u l l o w a y ( 19 9 5, 19 96 ) h a s a r g u e d t h a t i t i s u l t i m a t e l y t h e i r
s e c u r i ty i n t h e i r e x p e c t a t io n o f p a r e n t a l f a v o r i t i s m t h a t m a k e s f i r s tb o r n
c h i l d r e n d e f e n d e r s o f p a r e n t a l v a l u e s a n d t h e s t a t u s q u o w h i l e l a te r b o r n s
a r e r e l a t iv e l y i n c l i n e d t o b e " r e b e l s . "
I n a d d i t i o n t o t h e s e c u r i ty o f p a r e n t a l p r e f e r e n c e s , f i rs t b o rn s h a v e a l w a y s
b e n e f i t t e d f r o m a n e a r ly a b s e n c e o f s ib l in g c o m p e t i t i o n f o r p a r e n t a l i n v e s t -
m e n t ( Ja c o bs a n d M o s s 1 9 76 ). H o w e v e r , t h e r e i s a c o u n t e r v e i l i n g e f fe c t i nt h a t a s p a r e n t s t h e m s e l v e s g r o w o l de r , t h e f i tn e s s v a l u e o f a n o f f s p r i n g o f
a n y g i v e n a g e a n d p h e n o t y p e i n c re a s e s r e la t iv e t o th e p a r en t s " re s i d u a l r e -
p r o d u c t i v e v a lu e . T h u s , o l d e r p a r e n t s w i ll h a v e a t e n d e n c y t o i n v e s t m o r e
i n o f f s p r i n g , a ll e l s e b e i n g e q u a l , t h a n y o u n g e r p a r e n t s ( C l u t t o n - B r o c k 1 98 4;
P u g e s e k 1 99 5).
A l t h o u g h t h e i r i n it ia l u n c o n t e s t e d s t a tu s a n d t h e ir g r e a t e r f i tn e s s v a l u e
g i v e s f i rs t b o rn s a n a d v a n t a g e i n th e b a t tl e o f c o u r t i n g p a r e n t a l i n v e s t m e n t
( D a v is 1 9 97 ), t h is a d v a n t a g e m a y b e o f f se t b y a g r o w i n g w i l l i n g n e s s o f
a g i n g p a r e n t s t o g i v e m o r e o f t h e m s e l v e s t o t h e b e n e f i t o f t h e i r la t e r b o r ny o u n g . M o r e o v e r , a s S u l l o w a y (1 99 6:3 05 ) n o t e s , a l a s t b o r n c h i l d h a s t h e
Birth Order and Attitudes toward Family and Friends 75
p o r t t h a t m i d d l e b o r n s f in d p a r e n t s t o b e l e ss s u p p o r t i v e ( e m o t i o n a l l y a n d
f in a n c i a ll y ) t h a n d o f i r s tb o r n s a n d l a s tb o r n s .
B a s e d o n th e n o t i o n th a t e v o l v e d m o t i v a t io n a l m e c h a n i s m s h a v e b e e nd e s i g n e d t o e x p e n d a n o r g a n i s m ' s l i f e i n th e p u r s u i t o f g e n e t i c p o st e ri ty ,
o n e m i g h t e x p e c t n e p o t i s t i c s t ra t e g ie s o f i n v e s t m e n t a n d a n a t u r a l s o l id a r -
i t y b e t w e e n k in . S u c h b e h a v i o rs h a v e b e e n w e l l - d o c u m e n t e d i n m a n y
s p e c i e s ( f o r a n o v e r v i e w , s e e D a l y a n d W i l s o n 1 9 7 8 : c h a p . 3 ) , l e a d i n g t o -
w a r d a g e n e r a l e x p e c ta t io n o f b e n e v o l e n c e o r e m o t i o n a l a t t a c h m e n t t o
c lo s e k i n . S t u d ie s o f a l tr u i s m h a v e s u g g e s t e d , f o r e x a m p l e , t h a t t h e r e i s a
g r e a t e r e x p e c t a t i o n o f r e c e i v i n g h e l p f r o m p a r e n t s a n d s i b li n g s th a n f r o m
c l o s e f r i e n d s o r s t r a n g e r s ( B ar -T a l e t a l. 1 97 7; C u n n i n g h a m 1 98 6).
T h i s e m p h a s i s o n f i rs t b o rn s a n d l a s tb o r n s ( in te r m s o f p a r e n t a l i n v e s t -
m e n t ) s u g g e s t s t h a t i t m a y b e t h e m i d d l e b i r t h o r d e r p o s i t i o n s t h a t d e r iv e
t h e l e a s t b e n e f i t f r o m n e p o t i s t i c s o l i d a r i t y ( K e n n e d y 1 9 8 9 ; K i d w e l l 1 9 8 2 ;
S a l m o n a n d D a l y 1 998). I n s u p p o r t , S a l m o n a n d D a l y ( 1998) f o u n d t h a t
m i d d l e b o r n s d e c l a re t h e m s e l v e s t o b e l e ss c lo s e t o p a r e n t s ( a n d m o r e s o to
f r i e n d s a n d s i b l i n g s ) t h a n f i r s t b o r n s o r l a s t b o r n s a n d l e s s l i k e l y t o b e a c -
t i v e ly i n t e r e s t e d i n t h e i r f a m i l y h i s t o r ie s , o r t o m a k e k i n t ie s a p a r t o f t h e i r
s e lf -i de n ti ty . M i d d l e b o r n s w e r e a ls o f o u n d t o b e l e s s i n f l u e n c e d b y t h e
r h e t o ri c o f k i n s h i p a n d f a m i l y s o l i d a r i t y w h e n u s e d i n e v o c a t i v e p o l i t ic a l
s p e e c h . I n fa c t, r n i d d l e b o r n s w e r e m o r e l i k e ly to b e i n f l u e n c e d b y t e r m s o f
f r i e n d s h i p ( S a l m o n 1 99 8). I f m i d d l e b o r n s a r e l e s s a f f il ia t e d w i t h f a m i l y , a r e
t h e y i n s t e a d s p e c i a li z in g i n n o n - k i n r e c i p ro c a l r e l a ti o n s h i p s ? D o t h e y h a v e
m o r e p o s i t iv e a t t i t u d e s t o w a r d f r ie n d s h i p s a n d h e l p i n g p e o p l e o t h e r t h a n
k in ? A n d w h a t a b o u t m a t e s h i p s ?
In Born to Rebel, F r a n k S u l l o w a y ' s (1996) w i d e l y d i s c u s s e d e x a m i n a t i o n
o f b i r t h o r d e r a n d p e r s o n a l it y , h e p r o p o s e s t h a t i n d i v i d u a l d i f f e re n c e s in
r o m a n t i c lo v e st y le s o w e t h e m s e l v e s p r e d o m i n a n t l y to th e n o n - s h a r e d e n -
v i r o n m e n t . O t h e r s t u d i e s ( D r a p e r a n d H a r p e n d i n g 1982; S u r b e y 1990)
h a v e s u g g e s t e d t h a t o f fs p r in g w h o g r o w u p i n h o m e s w i t h i n c o n s i s t e n t o r
r e j e c ti n g c h i l d - r e a r i n g p r a c t i c e s t e n d t o r e a c h p u b e r t y e a r li er , to e n g a g e i n
i n t e r c o u r s e e a r l i e r , a n d t o h a v e m o r e s e x u a l p a r t n e r s t h a n c h i l d r e n w h o
h a v e g r o w n u p i n s ta b le a n d l o v in g h o m e s . I t a p p e a r s t h a t h a v i n g l e a r n e d
t h a t t h e y c a n n o t c o u n t o n p a r e n t a l i n v e s t m e n t , o f f s p ri n g f r o m u n s t a b l e
h o m e s s e e m t o b e m o r e l i k e ly to o p t f o r s h o r t - t e r m m a t i n g s tr a te g ie s . A t -
t a c h m e n t t h e o r i s t s h a v e a l so s u g g e s t e d t h a t d i f f e re n t s o r ts o f e a rl y c h i ld -
h o o d e x p e r ie n c e s m i g h t p r o d u c e i n d i v i d u a l d i f f e re n c e s in p r e f e re n c e f o r
l o n g - te r m c o m m i t t e d v e r s u s s h o r t- t e r m u n c o m m i t t e d r o m a n t i c r e l at i on -s h i p s ( B o w l b y 1 97 3; H a z e n a n d S h a v e r 1 98 7).
r e l a ti o n s h i p s w i t h f r ie n d s b u t a l so i n r e l a ti o n s h i p s w i t h m a t e s . I n s t e a d o f
e n g a g i n g i n m o r e s h o r t -t e r m m a t i n g s tr at eg ie s , t h e y m i g h t p l a c e a h i g h
v a l u e o n m a i n t a i n i n g a l o n g - t e r m c o m m i t t e d re l a ti o n s h ip , t re a t i n g t h e irm a t e i n m u c h t h e s a m e w a y a s t h e y t re a t th e i r fr i en d s , a s a v a l u e d r e c i p -
r oca l r e l a t i ons h i p .
I f m i d d l e b o r n s f e e l t h a t t h e y c a n n o t c o u n t o n p a r e n t a l i n v e s t m e n t , w i ll
t h e y t e n d t o fo l lo w a m o r e s h o r t - t e rm m a t i n g s t r at e g y ? P e r h a p s b e m o r e
p r o n e t o i n f id e l i ty ? O r w i l l t h e y b e l e s s li k e l y t o f o l lo w s u c h p a t t e r n s , i n -
t e r a c ti n g w i t h m a t e s m u c h a s t h e y d o w i t h f r i e n d s ? S o c i o se x u a l it y s c o re s
(S O I) m a y p r o v i d e s o m e i n s ig h t . I n d i v i d u a l s a t t h e l o w e n d o f th i s c o n -
s t r u c t , t h o s e w i t h a r e s t r i c t e d s o c i o s e x u a l o r i e n t a t i o n , t y p i c a l l y i n s is t o n
c o m m i t m e n t a n d c l o s e n e ss i n a re l a t io n s h i p p r i o r t o e n g a g i n g i n se x w i t h
a r o m a n t i c p a rt n e r. P e r s o n s a t th e h i g h e n d o f t h e c o n s t ru c t , th o s e w i t h a n
u n r e s t r i c t e d s o c i o s e x u a l o r i e n t a t i o n , t e n d t o f e e l r e l a t i v e l y c o m f o r t a b l e e n -
g a g i n g i n se x w i t h o u t c o m m i t m e n t o r c lo s en e ss (S i m p s o n a n d G a n g e s t a d
1 99 1). F o r t h e m o s t p a r t , t h e r e i s a c o n s i s t e n t s e x d i ff e r e n c e , w i t h m a l e s
t e n d i n g t o b e m o r e u n r e s t r i c t e d t h a n f e m a l e s , b u t t h e r e i s s u b s t a n t ia l
w i t h i n - s e x v a r i a t i o n a s w e l l . B i r th o r d e r d i f f e r e n c e s m a y a l s o e x is t, re f l e c t-
i n g t h e i m p o r t a n c e o f n o n - k i n s e x u a l r e la t i o n s h ip s t o m i d d l e b o r n s .
T h i s s t u d y b e g i n s t o e x p l o r e t h e i d e a t h a t i f m i d d l e b o r n s a r e le s s af fi li -
a t e d w i t h f a m i ly , a r e t h e y i n s t e a d s p e c i a l i z in g i n n o n - k i n r e c i p r o c a l r e l a -
t i o n s h ip s , w i t h t h e f o l l o w i n g p r e d i c ti o n s :
Prediction 1: M i d d l e b o r n s w i l l h a v e l e s s p o s i t i v e a t t i t u d e s t h a n f i r s t -
b o r n s o r l a st b o r n s t o w a r d f a m i l y i n g e n e r a l.
Prediction 2: M i d d l e b o r n s w i l l h a v e l e s s p o s i t i v e a t t i t u d e s t h a n f i r s t -
b o r n s o r l a s tb o r n s t o w a r d h e l p i n g f a m i l y i n n e e d .
Prediction 3: M i d d l e b o r n s w i ll h a v e m o r e p o s i t iv e v i e w s t h a n f i rs t b o rn s
o r l a st b o r n s t o w a r d f r i e n d s a n d f r i e n d s h i p in g e n e r a l .
Prediction 4: M i d d l e b o r n s w i l l b e l e s s li k e ly to s e e t h e m s e l v e s a s o n e o f
t h e i r p a r e n t s ' f a v o r i te s .
Prediction 5: M i d d l e b o r n s w i l l h a v e l o w e r ( m o r e re s tr i ct e d ) s o c io s e x u a l-
i t y s c o re s t h a n f i r st b o r n s o r l a s t b o r n s a n d , i n p a r t i c u l a r, b e l e s s l ik e l y
t o c h e a t o n a p a r t n e r w h e n i n a c o m m i t t e d r e l a t i o n s h i p ( a s t h a t
p a r t n e r i s a n o n - k i n s o c ia l, a s w e l l a s s e x u a l , r e s o u rc e ) .
M E T H O D S
T w o h u n d r e d a n d f o rt y -f iv e S i m o n F r a s e r U n i v e r s i ty u n d e r g r a d u a t e s tu -
Birth Order and Atti tu de s toward Fam ily and Friends 77
t w e n t y - s e v e n s u b je c ts . S e v e n t y s u b j ec t s w e r e m a l e , th e o t h e r o n e h u n d r e d
a n d f i f ty - s e v e n w e r e f e m a l e . T h e r e w e r e n i n e ty - s ix f i rs tb o r n s , s e v e n t y - t w o
m i d d l e b o r n s , a n d f if ty - n in e l a s tb o r n s . T h e q u e s t i o n n a i r e t o o k a h a l f h o u rt o c o m p l e t e , a n d s u b je c t s r a n g e d i n a g e f r o m e i g h t e e n t o t h i r t y - tw o .
N i n e t y - o n e p e r c e n t w e r e s i n g l e , t h e r e s t w e r e m a r r i e d o r l i v i n g w i t h a
p a r tn e r . T h e m a j o r i ty o f th e s u b j ec t s c a m e f r o m m i d d l e i n c o m e ( o r m i d d l e -
c l a s s ) f a m i l i e s .
S u b je c ts w e r e a s k e d a s e ri es o f d e m o g r a p h i c q u e s t i o n s . T h e y w e r e a l s o
a s k e d a b o u t p a r e n t a l f a v o r i t i s m a n d q u e s t i o n s c o n c e r n i n g t h e i r a t t i -
t u d e s / b e l i e f s a b o u t f a m i l y l i f e ( t h e F a m i l i a l O r i e n t a t i o n s c a l e , a d a p t e d
f r o m R u n d q u i s t a n d S l e tt o 1 93 6, w h i c h m e a s u r e s p o s i t i v e o r n e g a t i v e a t t i-
t u d e s t o w a r d f am i ly ) . O n e e x a m p l e o f t h e t y p e o f s t a t e m e n t th a t m a k e s u p
t h is F a m i l y S e n t i m e n t s c al e is " A p e r s o n s h o u l d b e w i l l i n g t o sa c ri fi ce a n y -
t h i n g f o r o n e ' s f a m i ly . "
S u b je c ts a ls o c o m p l e t e d t w o m e a s u r e s o f h e l p i n g b e h a v i o r ( o n e se t o f
q u e s t i o n s a d d r e s s e d h e l p i n g f a m i l y m e m b e r s , t h e o t h e r s e t a d d r e s s e d
h e l p i n g s t r a n g e r s o r p e o p l e i n g e n e ra l ) . O n e e x a m p l e f r o m t h e h e l p in g -
r e l a t i v e s s c a l e w a s " A r e la t iv e i n n e e d c a n b e a n u i s a n c e " ; o n e f r o m t h e
h e l p i n g n o n - k i n s ca le w a s " I n g e n e ra l , w e s h o u l d n o t a l lo w o u r s e l v e s to
b e d i s t r e s s e d b y t h e m i s f o r t u n e o f o t h e r p e o p l e . " S u b j ec t s a ls o c o m p l e t e d
a sc a le m e a s u r i n g a t t i t u d e s t o w a r d f r i e n d s h i p ( a d a p t e d f r o m P a r k e r a n d
A s h e r 1 993). I t i n c l u d e d i t e m s l ik e " M y f r i e n d s a n d I c a n c o u n t o n e a c h
o t h e r t o k e e p p r o m i s e s . " A l l o f th e s e a t t i t u d i n a l q u e s t i o n s a s k e d f o r ra t -
i n g s o n a 5 - p o i n t L i k e r t - t y p e s c a l e , r a n g i n g f r o m s t r o n g l y a g r e e ( 5 ) t o
s t r o n g l y d i s a g r e e ( 1 ) . S u b j e c t s w e r e a l s o g i v e n t h e s o c i o s e x u a l i t y s c a l e
( G a n g e s t a d a n d S i m p s o n 1 99 0) a s w e l l a s s ev e r a l o t h e r q u e s t i o n s a d d r e s s -
i n g t h e i r s e x u a l b e h a v i o r w h i l e i n a c o m m i t t e d r e l a t i o n s h ip .
T h e m o s t f r e q u e n t l y u s e d s ta ti st ic a l m e a s u r e w a s t h e A N O V A (F v a l u e s
r e p o r t e d ) . I t w a s u s e d t o a n a l y z e t h e d a t a o n f a m i l y s e n t i m e n t a n d o b l ig a -
t io n , h e l p i n g a t t i t u d e s , a n d s o c io s e x u al it y . T h e c h i - sq u a r e w a s u s e d t o ex -
a m i n e t h e d a t a o n c h e a t in g o n o n e ' s p a r t n e r.
RESULTS
W h e n s u b j e c t s w e r e a s k e d a s e ri e s o f q u e s t i o n s a d d r e s s i n g f a m i l y se n t i-
m e n t a n d o b l i g a t i o n ( t h e F a m i l i a l O r i e n t a t i o n s c a l e ) , m i d d l e b o r n s e x -
p r e s s e d s i g n if ic a n t ly le s s p o s i t i v e a t t i tu d e s t o w a r d f a m i l y t h a n f i rs t b o r n so r l a s t b o r n s , F ( 2 , 1 1 1 = 6 . 9 4 , p < 0 . 0 0 1 . A T u k e y ' s H S D t e s t r e v e a l e d t h a t t h e
f i rs t b o r n s m i d d l e b o r n s l a s t b o m s
B i rt h O r d e r
F i g u r e 1 . Scores on fam ily and familial ob ligation scale wit h resp ect to bir th order.H ighe r scores indicate more pos i t ive v iew s of family l ife and familial obl iga-tions.
a t t i t u d e s t o w a r d h e l p i n g k i n i n n e e d , m i d d l e b o r n s w e r e s i g n if ic a n tl y le s s
l ik e l y t h a n f i rs t b o r n s o r la s t b o r n s t o h a v e p o s i t i v e a t t it u d e s t o w a r d h e l p -i n g f a m i l y m e m b e r s i n n e e d , F ( 2,m ) = 6 .8 9 , p < 0 .0 02 . A g a i n , a T u k e y ' s H S D
t e s t r e v e a l e d s ig n i fi c an t d i f f er e n c e s b e t w e e n f i rs t b o r n s a n d m i d d l e b o r n s
( p < 0 .0 0 5) a n d b e t w e e n l a s t b o r n s a n d m i d d l e b o r n s ( p < 0 .0 0 2) , a n d n o s i g -
n i fi c a n t d i f fe r e n c e b e t w e e n f i r s tb o r n s a n d l a s tb o r n s . H o w e v e r , w h e n t h e
q u e s t i o n s a d d r e s s e d h e l p i n g s t r a n g e r s , t h e r e w e r e n o b i r t h o r d e r d i f f e r -
e n c e s , F (2 ,m ) = 0 .5 9 , n . s. A l l b i r t h o r d e r s h a d l e s s p o s i t i v e a t t i t u d e s t o w a r d
h e l p i n g s t r a n g e r s t h a n h e l p i n g k i n.
S u b j e c t s w e r e g i v e n a s e ri e s o f s t a t e m e n t s a b o u t a t t i tu d e s t o w a r d
f r ie n d s a n d f r ie n d s h i p a n d a s k e d h o w t ru e s u c h a s ta t e m e n t w a s f o r t h em .M i d d l e b o r n s e x p r e s s e d s i g n i f i c a n t l y m o r e p o s i t i v e v i e w s o n f r i e n d s h i p
Birth O rder and Att itud es toward Family and Friends
44 .
79
42 -
3 8 -
O
t,- 34-
0
~aa.0
C
2 6 -
Z4 .
2 2 .
2 0 4
f i r s tb o r n s m i d O l e b o m s l a s t b o m s
B ir th O r de r
Figure 2. Scores on attitudes toward helping family scale with respect to birthorder. Higher scores indicate more positive views toward helping familymembers in need.
When subjects were asked about their parents havi ng a favorite child,
very few subjects claimed to be the favorite and almost no parents were re-
port ed to share the same favorite child. Interestingly, of the 95 subjects that
responded, 64% said tha t their mother's favorite child was a son. In termsof birth order, 45% of the subjects" mothers favored a firstborn, 22% a mid-
dleborn, and 33% a lastborn child. For the 107 subjects who responded
about their father 's favorites, 60% of fathers favored a daughter. In terms
of birth order, 36% of fathers favored a firstborn, 21% a middleborn, and
43% a lastborn child. When only sibships of three were considered, mid-
dleborns were significantly less likely tha n firstborns or lastborns to be
chosen as a parenta l favorite , ~22 = 12.9, p < 0.01. Middleborns seem least
likely to be a parental favorite, and parents tend to favor an opposite-sex
offspring.In terms of the sociosexuality scores, the typical sex difference with
Figure 3. Scores on at t i tude s tow ard h elping friend s and friendsh ip scale with re-spec t to bi rth order. High er scores indica te m ore po s i tive views o f f r iends a ndfriendship in general.
b i r th o r d e r e f fe c t w a s f o u n d , w i t h m i d d l e b o r n s s c o r in g l o w e r o n t h e S O I
t h a n f i r s t b o r n s o r l a s t b o r n s . I n t e r e s ti n g l y , i n t e r m s o f i n f i d e l i t y i n p a r t i c u -
la r, m i d d l e b o r n s r e p o r t e d " c h e a t in g " o n a p a r t n e r i n a " m o n o g a m o u s " r e-
l a t io n s h i p s i g n i fi c a n tl y le s s t h a n d i d f i r st b o r n s o r l a s t b o m s , ~ 2 2 -----14.30, p
< 0 .0 01 . In t e r m s o f th e n u m b e r o f t i m e s s u c h a n i n c i d e n t o f c h e a t i n g h a d
o c c u r r e d , t h e r e w a s n o s i g n if i ca n t b i r t h o r d e r d i f f e r en c e , t h o u g h f i r s tb o r n sd i d s o w i t h s l ig h t ly g r e a t e r f r e q u e n c y t h a n o t h e r b i r th o r d e r s .
I t is w o r t h n o t i n g t h a t b i r t h o r d e r e f f ec t s i n th i s s t u d y w e r e n o t a n a r t i-
f a c t o f fa m i l y si ze . O n e m i g h t e x p e c t th a t c h i l d r e n i n p a r t i c u l a r l y l a r g e
f a m i l ie s w o u l d r e c e i v e l es s a t t e n t io n a n d c a r e f r o m p a r e n t s t h a n c h i l d r e n
i n sm a l l er f a m ili es . H o w e v e r , p r e v i o u s w o r k ( S a lm o n a n d D a l y 1 99 8) h a s
s h o w n t h a t o n v a r i a b l e s o f f a m i li a l s e n t i m e n t , s i b s h i p s i z e ( w h e n f o u r o r
l e s s ) h a s n o s i g n i f i c a n t i m p a c t . I n t h i s s t u d y , a l l s u b j e c t s c a m e f r o m s i b -
Birth Order and Attitudes toward Fam ily and Friends 81
n o
9 firstborns
9 middleborns
lastborns
Figure 4. Percentage of subjects , by birth order, w ho hav e "ch eated" o n their part -n e t .
t h e r e p r o d u c t i o n o f a n i n d i v i d u a l ' s g e n e s ( H a m i l to n 19 64 ). B a s e d o n t h e
c o n c e p t th a t e v o l v e d m o t i v a ti o n a l m e c h a n i s m s h a v e b e e n d e s i g n e d t o ex -
p e n d a n o r g a n i s m ' s l if e i n th e p u r s u i t o f g e n et ic p o s t er it y , o n e m i g h t
e x p e c t n e p o ti s ti c s t r at e g ie s o f in v e s t m e n t a n d a n a t u r a l s o l id a r i ty b e t w e e n
k i n . A c t i v i t i e s t h a t p r o m o t e s u c h g e n e t i c s u r v i v a l i n c o n s p e c i f i c s a r e r e -
f e r re d t o a s k i n i n v e s t m e n t , o f w h i c h p a r e n t a l i n v e s t m e n t i s t h e m o s t f u n -d a m e n t a l . T h i s s t u d y a d d r e s s e d i s su e s o f k i n i n v e s t m e n t i n t e rm s o f t h ei r
i n f l u e n c e o n i n d i v i d u a l s o f v a r y i n g b i r t h o r d e r s . I n p a rt ic u l a r, p r e d i c t i o n s
a b o u t t h e a tt i tu d e s t h a t m i d d l e b o r n s ( as o p p o s e d t o f ir s tb o r n s a n d l as t-
b o r n s ) h o l d t o w a r d f a m i l y , f r ie n d s , h e l p i n g b e h a v i o r , a n d p a r e n t a l f a -
v o r i t i s m w e r e e x a m i n e d , a s w e l l as th e i r s o c i o s e x u a l i ty sc o r es . T h e s e a r e a s
w i l l b e d i s c u s s e d s e p a r at e ly .
F a m i l i a l S e n t i m e n t
P r e v i o u s r e s e ar c h h a s s u g g e s t e d t h a t m i d d l e b o r n s f ee l l es s cl o se to p a r -
8 2 H u m an N a t u re , V o l. 1 4, N o . 1 , 2 0 03
o b l i g a t i o n , m i d d l e b o r n s e x p r e s s e d s i g n if i ca n t ly l es s p o s i t i v e a t t i tu d e s t o-
w a r d f a m i l y t h a n f i rs tb o r n s o r l a s t b o m s . I n a d d i t io n , m i d d l e b o r n s w e r e
s i g n i f ic a n t l y l e ss l i k e l y t h a n f i r s tb o r n s o r l a s t b o r n s t o h a v e p o s i t i v e a t ti -t u d e s t o w a r d h e l p i n g f a m i ly m e m b e r s in n e e d ( w h i le t h e re w e r e n o b i r t h
o r d e r d i f f e re n c e s w i t h r e s p e c t to h e l p i n g s t ra n g e r s ) .
A s m e n t i o n e d e a r li er , f i r s tb o r n s s e e m s e c u r e i n te r m s o f p a r e n t a l p r e f e r -
e n c e ( D a l y a n d W i l s o n 1 98 4); t h e y a l so g e t a h e a d s t a r t o n p a r e n t a l i n v e s t -
m e n t b y b e I n g t h e o n l y o f f s p r i n g u n t i l th e i r s ib l in g s c o m e a l o n g . B u t i t is
a ls o t r u e t h a t t h e v a l u e o f e a c h o f f s p r i n g in c r e a s e s r e l a ti v e t o e a c h p a r e n t ' s
r e s i d u a l r e p r o d u c t i v e v a l u e w i t h i n c r e a s in g p a r e n t a l a g e ( P u g e s e k 1995).
A s a r e s u lt , l a s t b o r n s s h o u l d a l so e x p e r ie n c e e n h a n c e d i n v e s t m e n t f r o m
p a r e n t s a s t h e y r e p r e s e n t t h a t l a st o p p o r t u n i t y f o r p a r e n t s t o in v e s t in d i -
r e c t o f f s p r i n g . A s a r e s u l t , m i d d l e b o r n s s e e m t o l o s e o u t i n t e r m s o f
p a r e n t a l i n v e s t m e n t . U n s u r p r i s i n g l y , t h e r e f o r e , f i r s t b o r n s a n d l a s t b o r n s
a p p e a r t o id e n t i fy m o r e s t ro n g l y w i t h f a m i l y m e m b e r s a n d a re m o r e p o s -
i t i v e a b o u t h e l p i n g k i n t h a n m i d d l e b o r n s , w h o a r e l e s s p o s i t i v e t o w a r d
h e l p i n g f a m i ly a n d s e e m t o h a v e m o r e p o s i t i v e a t t i tu d e s t o w a r d f r i en d s .
F r i en d s a n d F r i e n d s h i p
T h e s i b s h i p s i n t o w h i c h h u m a n s a r e b o r n a r e c r u c i a l s o c i a l e n v i r o n -
m e n t s w i t h a s s o c ia t e d o p p o r t u n i t i e s , c o s ts , a n d " n i c h e s ," a n d i t w o u l d b e
r e m a r k a b l e i f o u r e v o l v e d s o c ia l p s y c h e s d i d n o t c o n t a i n f e a tu r e s a d a p t e d
t o t h e p e c u l i a r i t i e s o f s i b l i n g r e l a t i o n s h i p s . S u l l o w a y ( 19 9 5, 19 96 ) d e v e l -
o p e d t h e i d e a o f n i c h e d i f f e re n t ia t io n w i t h p r i n c i p a l r e f e r e n c e to t h e w a y s
i n w h i c h o n e d e a l s w i t h o n e ' s o r d i n a l p o s i t io n i n a s ib s h i p . E v o l u t i o n a r y
c o n s i d e r a t i o n s s u g g e s t t h a t p a r e n t s w o u l d f a v o r t h e i r e l d e s t o f f s p r i n g
( A l e x a n d e r 1 9 79 ), a n d w h e n t o u g h c h o i c e s a re r e q u i r e d , t h e r e is e v i d e n c e
t h a t t h e y d o j u s t t h a t ( D a ly a n d W i ls o n 1 984). A s a r e s u lt , m i d d l e b o r n s a p -
p e a r t o b e l e s s a f f i l ia t e d w i t h k i n . T h e y a r e c e r t a i n l y l e s s s u s c e p t i b l e t o t h e
u s e o f k i n t e r m s i n p o l i t i c a l s p e e c h ( S a l m o n 1 99 8).
I t h a s b e e n s u g g e s t e d t h a t if m i d d l e b o r n s a r e le s s f a m i l y o ri e n t e d , th e y
a r e i n s t e a d s p e c i a l iz i n g i n n o n - k i n r e c i p r o c a l r e l a ti o n s h i p s . I f m i d d l e b o r n s
r e ce iv e l e ss i n v e s t m e n t o n a v e r a g e f r o m k i n , th e y m i g h t b e e x p e c t e d t o s e e k
r e c ip r o c a l ti es e l se w h e r e , p e r h a p s p r i m a r i l y i n t h e b o n d s o f fr i e n d s h i p . S Ul-
l o w a y (1 99 6) h a s p r o p o s e d t h a t r e b e l l i o u s n e s s , r i s k - ta k i n g , d i v e r s i t y o f i n -
t e r e s t s , a n d c o o p e r a t i v e n e s s a r e l a t e r b o r n s t r a t e g i e s t o a c q u i r e a l a r g e r
s h a r e o f p a r e n t a l r e s o u r c e s . B u t t h e s e tr a it s m i g h t a ls o a i d m i d d l e b o r n s i np a r t i c u la r , n o t i n a c q u i r i n g p a r e n t a l i n v e s t m e n t , b u t i n e s ta b l i s h in g r e c i p -
Birth Order and Atti tud es toward Family and Friends 83
g e s t i n g t h e i m p o r t a n c e o f s u c h r e l a t i o n s h i p s i n t h e i r l i v e s . T h i s r e s u l t
e c h o e d t h e s u s c e p t ib i li ty o f m i d d l e b o r n s t o t h e u s e o f te r m s o f f r i e n d s h i p
a s o p p o s e d t o k i n t e r m s i n p o l it ic a l r h e t o r ic ( S a l m o n 1 9 98 ). T h e s e r e s u l t sr a is e t h e p o s s ib i li ty t h a t p e e r i n f l u e n c e m i g h t a l s o b e g r e a t e r a m o n g s t m i d -
d l e b o r n c h i ld r e n , a f in d i n g th a t w o u l d m e s h w e l l w i t h c u r r e n t w o r k o n
p e e r i n f l u e n c e i n s c h o o l a g e c h i l d r e n ( H a r r i s 1 998 ). S u c h w o r k h a s s u g -
g e s t e d a l a r g e ro l e f o r p e e r i n f l u e n c e (a s o p p o s e d t o p a r e n t a l i n f l u en c e ) ,
s o m e t h i n g t h a t m i g h t b e s e e n i n h i g h e r le v e ls a m o n g t h e m a n y m i d d l e -
b o r n s i n t h e p o p u l a t i o n .
Mo m m y ' s L i t t l e Bo y a n d D a d d y ' s L i t t l e G i f tC o m m o n s a y in g s re g a r d i n g " M o m m y ' s L it t le B o y " a n d " D a d d y ' s L it t le
G i rl " b e g t h e q u e s t io n , a r e m i d d l e b o m s o f t e n l ef t o u t b e c a u s e b o t h p a r e n t s
h a v e a f a v o r i te c h i l d a n d t h e m i d d l e o n e i s n ' t a fa v o r it e ? W h e n s u b je c ts
l i s t e d a p a r e n t a l f a v o r i t e , m o t h e r ' s f a v o r i t e t e n d e d t o b e a f i r s t b o r n s o n ,
w h i l e d a d d y ' s f a v o r it e w a s m o s t li k el y a l a st b o rn d a u g h t e r . M i d d l e b o r n s
d o a p p e a r t o b e t h e l e as t n u m e r o u s b i rt h o r d e r a m o n g p a r e n t a l f av o ri te s ,
a n d p a r e n t s t e n d e d t o f a v o r a n o p p o s i te - s e x o ff s p ri n g .
W h i le e x a m i n i n g b i r t h o r d e r a n d p a r e n t a l f a v o ri ti s m is s o m e w h a t n o v e l ,
t h e r e h a s b e e n p r e v i o u s w o r k o f a t h e o r e t i c a l a n d e m p i r i c a l n a t u r e o n
p a r e n t - o f f s p r i n g c o n f li c t a n d w h e t h e r i t is s e x - li n k e d . F r e u d ' s t h e o r ie s
(1910 , 1953) a b o u t p a r e n t - o f f s p r i n g f a n t a s i e s a r e w e l l k n o w n , f a n t a s i e s
a b o u t m a t i n g w i t h t h e o p p o s i te - se x p a r e n t a n d r e s e n ti n g th e s a m e - s e x p a r -
e n t a s a r i v a l ( F r e u d 1 92 5). D a l y a n d W i ls o n ( 19 89 ) h a v e e l e g a n t l y c r i t i q u e d
t h is p e r s p e c t i v e , s u g g e s t i n g t h a t F r e u d c o l l a p s e d t w o d i s ti n c t f a th e r - s o n
c o n fl ic ts in t o o n e : a n e a r l y c o n f li c t o v e r h o w a w o m a n ' s r e p r o d u c t i v e r e -
s o u r c e s a r e to b e a l l o c a t e d ( i nt o h e r e x i st in g s o n v s . m o r e m a t i n g s ) a n d a
l a te r r i v a l ry t h a t is s e x u a l b u t i n v o l v e s w o m e n o t h e r t h a n t h e m o t h e r , s u c h
a s ju n i o r w i v e s i n a p o l y g a m o u s s o c i e t y (B o o n e 1 9 88 ; L e V i n e 1 9 65 ).
Ma t i n g S t r a t e g i e s
W a l le r a n d S h a v e r (1 99 4) d e m o n s t r a t e t h a t i n d i v i d u a l d i f f e r e n c e s i n r o -
m a n t ic l o v e st y le s a r e p r e d o m i n a n t l y o w i n g t o n o n - s h a r e d e n v i r o n m e n t s ,
r a i si n g t h e p o s s i b il it y t h a t l o v e s t y l es m a y b e r e s p o n s i v e t o t h e f a m i l y e n -
v i r o n m e n t i n w h i c h a n i n d i v i d u a l h a s b e e n r a i s e d . R e s e a r c h h a s a l s o
s h o w n , f o r e x a m p l e , t h a t o f f s p ri n g r a i s e d i n h o u s e s w i t h i n c o n s i s t e n t o rr e j e c ti n g c h i l d - r e a r i n g p r a c t ic e s t e n d t o r e a c h p u b e r t y e a r l i e r, e n g a g e i n i n -
m i g h t b e m o r e l ik e l y t h a n t h e i r o l d e r s ib s t o e n g a g e i n h i g h - r i sk s t r a te g i e s
s u c h a s m a t e p o a c h i n g a n d i nf id e li ty .
A s h a s b e e n f o u n d i n p r e v i o u s s t u d i e s ( G a n g e s t a d a n d S i m p s o n 1 9 9 0 ;G a n g e s t a d e t al. 19 92 ), m a l e s h a d h i g h e r S O I s c o r e s i n g e n e r a l . W h e n t h e
i n te r a c ti o n b e t w e e n s ex a n d b i rt h o r d e r w a s e x a m i n e d , it b e c a m e c le a r
t h a t , fo r f e m a l e s b u t n o t m a l e s , t h e r e w a s a s i g n i fi c a n t i m p a c t o f b i r t h
o r d e r, w i t h m i d d l e b o r n s h a v i n g l o w e r S O I s c or e s t h a n f ir s tb o r n s o r la s t-
b o r n s . H o w e v e r , th e r e w a s n o s u c h e f fe c t i n m a l e s, p e r h a p s b e c a u s e w h i l e
f e m a l e s a r e a s e x u a l r e s o u r c e f o r m a l e s , t h e y a r e l e s s l i k e l y to b e a s o c i a l re -
s o u r c e in t h e w a y m a l e s u p p o r t c a n b e f o r f e m a l es . I t i s a ls o p o s si b le t h a t
t h e m a l e i n c l i n a t i o n t o w a r d u n r e s t r i c t e d s o c i o s e x u a l i t y c r e a t e s a f lo o r e f -
f ec t. I n d i r e c t t e r m s o f in f id e li ty , m i d d l e b o r n s r e p o r t e d h a v i n g c h e a t e d a t
l e a s t o n c e o n a s t e a d y p a r t n e r s i g n i f i c a n t ly l e ss t h a n f i r st b o r n s o r l a s t b o r n s
f o r b o t h s ex e s. So it lo o k s a s t h o u g h m i d d l e b o r n s a r e i n t e r a c t in g w i t h
m a t e s i n m u c h t h e s a m e w a y a s t h e y i n te r a ct w i t h f r ie n d s , b e i n g c a r e fu l to
m a i n t a i n h i g h - q u a l i t y r e l a ti o n s h i p s i n b o t h a r ea s .
O t h e r C o n s i d e r a t io n s
O n e f r a m e w o r k t h a t m a y b e u s e f u l f o r a c o n s i d e r a t io n o f t h e s e r e s u lt s is
t h a t o f a l te r n a t iv e s tr a te g i e s, w h i c h c o n c e r n s m o r p h o l o g i c a l , p h y s i o l o g i c a l
a n d b e h a v i o r a l d i v e r s i f i c a t i o n o f a l t e r n a t i v e p h e n o t y p e s w i t h i n s p e c i e s
( G r o s s 19 96 ). T h e i d e a o f a l t e r n a t i v e s t r a te g i e s w i t h r e s p e c t t o h u m a n p e r -
s o n a l i t y h a s b e e n d i s c u s s e d b y G a n g e s t a d (1 99 6). R e s e a r c h o n a l t e r n a t i v e
s tr a te g i e s i n n o n - h u m a n a n i m a l s h a s s h o w n t h a t in m o s t c a s e s t h e e n v i-
r o n m e n t p l a y s a l a r g e ro l e i n d e t e r m i n i n g t h e p u r s u i t o f p a r t ic u l a r t a ct ic s
w i t h i n a s t r a t e g y ( G r o s s 1 99 6). T h i s e m p h a s i s o n t e c h n i c a l p l a s t i c i ty i n r e -
s p o n s e t o t h e e n v i r o n m e n t m e s h e s w e l l w i t h t h e a r g u m e n t t h a t s ib li ng s
p u r s u e c o n t i n g e n t ta c ti cs in r e s p o n s e t o t h e f a m i l ia l e n v i r o n m e n t .
A l t h o u g h t h i s s t u d y a d d r e s s e s s o m e o f t h e is s u e s o f m i d d l e b o r n s ' r e la -
t i o n s h ip s w i t h f a m i l y, f r ie n d s , a n d m a t e s , a d d i t i o n a l q u e s t i o n s a r e r e l e v a n t
t o t h e s e is s u e s. A n e x p l o r a t i o n o f t h e re l a t i o n s h i p b e t w e e n b i r t h o r d e r , e x -
c h a n g e o ri e n ta t io n , a n d t h e v a l u e o f i te m s e x c h a n g e d w i t h f r ie n d s w o u l d
s e e m p a r t i c u l a r ly f r u it f u l w i t h r e g a r d t o t h e n a t u r e o f m i d d l e b o r n s a s re c i-
p r o c i t y s p ec ia li st s. I n a d d i t i o n , m o r e w o r k n e e d s t o b e d o n e o n b i r th o r d e r
a n d m e a s u r e s o f p a r e n t a l i n v e st m e n t . S o m e s t u d ie s h a v e s u g g e s t e d t h a t
m i d d l e b o r n s r e c e i v e l es s fi n a n ci a l s u p p o r t f r o m p a r e n t s ( K e n n e d y 1 98 9)
w h i l e o t h e r s h a v e s h o w n t h a t m i d d l e b o r n s c l e a rl y p e r c e iv e t h e m s e l v e s asl o s in g o u t i n t e r m s o f p a r e n t a l i n v e s t m e n t ( S a lm o n a n d D a l y 1 998 ; S a l m o n
Birth O rder and Attitu des toward Family and Friends 85
i m p a c t o f b i r t h o r d e r o n m a t i n g s t ra t e g ie s a l s o c l e a rl y n e e d s f u r t h e r e x a m -
i n at io n . I t m a y b e t h a t in a l a rg e r s a m p l e , t h e m i d d l e b o r n s w o u l d h a v e
s h o w n s i g n if ic a n t ly l o w e r S O I s c o re s . T h e y c e r ta i n l y w e r e l e s s l ik e l y toh a v e c h e a t e d o n a p a r t n e r w h i l e i n a c o m m i t t e d r e l a ti o n s h ip . I t w o u l d b e
b e n e f ic i a l t o l o o k a t th i s q u e s t i o n w i t h n o t o n l y a l a rg e r s a m p l e b u t w i t h o n e
m o r e d i v e r s e in a g e, si n ce a c o m m i t t e d r e l a t io n s h ip m a y m e a n s o m e t h i n g
q u i t e d i f f e r e n t a t 2 0 y e a r s o f a g e t h a n i t d o e s a t 3 0.
C O N C L U S I O N S
T h e s e r e s u l t s e c h o p r e v i o u s o n e s s u g g e s t i n g t h a t b i r t h o r d e r h a s a
s i g n i f i c a n t i m p a c t o n f a m i l i a l s e n t i m e n t , w i t h m i d d l e b o r n s b e i n g l e s s
f a m i l y - o r i e n t e d t h a n f i rs t b o rn s o r l a s tb o r n s . T h i s s t u d y a l s o s u g g e s t s t h a t
m i d d l e b o r n s p l a c e g r e a te r i m p o r t a n c e o n a n d h a v e m o r e p o s i ti v e v i e w s o f
n o n - k i n f r i e n d s h i p s t h a n f i rs t b o rn s o r la s t b o r n s, a g a i n s u g g e s t i n g t h a t t h e y
a r e s p e c i a l is t s in n o n - k i n r e c i p r o c a l a ll ia n c e s . T h i s i s s u e o f b i r t h o r d e r a n d
m a t i n g s t r a t e g ie s c l ea r ly n e e d s f u r t h e r e x p l o r a t io n . H o w e v e r , f e m a l e m i d -
d l e b o r n s ( n o t m a l e s ) h a v e l o w e r S O l sc o r es , a n d b o t h m a l e a n d f e m a l e
m i d d l e b o r n s w e r e l e s s li k e ly th a n f i rs t b o rn s o r l a s t b o r n s t o r e p o r t c h e a t i n go n t h e i r p a r t n e r s w h i l e i n a s t e a d y r e la t io n s h ip . O v e r a l l , t h e s e b i r t h o r d e r
d i f fe r e n c e s s u g g e s t t h e p o s s i b i li t y o f a l t e rn a t i v e s t ra t e g i e s b e i n g p u r s u e d
b y i n d i v i d u a l s i b li n g s a s a r e s p o n s e t o d i ff e r e n c e s i n t h e ir e x p e r i e n c e s o f
t h e fa m i l y e n v i r o n m e n t . S u c h s tr a te g ie s m a y i n d e e d b e w h y m i d d l e b o r n s
a p p e a r t o b e n o n - k i n r e c i p r o c a l r e l a t i o n s h i p s p e c ia l is t s.
The author w ou ld l ike to thank Frank S ul low ay and Char les Craw ford for theirsugges tions and supp or t as wel l a s two anon ym ous rev iewers fo r thei r he lp fu l
comments .
Catherine Salmon, Ph.D., is curre ntly a Michael Smith Fo und ation fo r H ealth Re-search Pos t-Doctoral Fel low in the Psyc holog y Dep ar tme nt of S imon Fraser Uni-versity in Burnaby, Brit ish Columbia. Her research interests include bir th order
and relat ionships , the l ink betw een reproduct ive supp ress ion an d anorexic be hav-ior , female sexual ity, an d the evolut ion ary s tu dy of l i tera ture an d the med ia .
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