“Same-Sex” and “Opposite-Sex” 63opposite- sex friendships. These adjectives have existed for as long as empirical
friendship studies have been conducted (Kirkpatrick, 1937; Vreeland & Corey,
1937), and they deceptively appear to be nonproblematic. Friendship investigators
routinely use these categories without a second thought as to what they really mean
or what groups are being excluded by the use of that typology. Employment of the
terms “same- sex” and “opposite- sex,” and operationalizing friendship studies based
on those concepts, is problematic, and friendship scholars need to more closely
examine them and the assumptions that are embedded in those adjectives.
What does it mean to state that two individuals are in a same- sex or opposite- sex
friendship and/ or that they are of the same or opposite sex from one another? What
decision rules are invoked when deciding whether a particular friendship is one or
the other? Why must the friendship be one or the other? If friendship scholars and
researchers believe that all friendships are either same- sex or opposite- sex (and it
appears that most do), at a minimum there should be agreement about what con-
stitutes biological sex. What biological traits make a person a female or a male? Are
they absolute? Are they universal? There is an extensive literature on these topics
that space limitations prevent us from thoroughly exploring, but a few observations
can be made that illustrate why the binary categorization of all friendships as either
same- sex or opposite- sex is fraught with difficulties.
Biologists struggle when trying to draw an absolute dichotomy between “male”
and “female,” because decision rules for distinguishing one biological sex from
another come with caveats, clarifications, and political agendas (Dreger, 1998;
Fausto- Sterling, 1999; Harper, 2007; Kessler, 1998). For example, anatomical dif-
ferences between two individuals are often the litmus test for deciding if they are of
opposite sexes. More than any other single factor, a person’s anatomy at birth deter-
mines whether that person is viewed by the medical establishment as male or female,
and biological sex assignment is initially made according to the presence or absence
at birth of male genitalia (Harper, 2007; Kessler, 1998). However, intersex individu-
als born with ambiguous genitalia make the assignment of biological sex based on
genitalia problematic (Harper, 2007). Some estimates conclude that roughly one
person in every 1,500 is born with ambiguous genitalia (Fausto- Sterling, 1999). By
mathematical extension, roughly 200,000 individuals in the United States are born
with mixed genitalia that render biological sex assignment difficult at best. If one’s
friend has both male and female genitalia, is that friend of the same or opposite sex
as oneself?
Chromosomal testing also appears to be an ironclad methodology for deter-
mining one’s biological sex, but it is not. Although an XY chromosome pair nor-
mally results in a male and an XX chromosome pair in a female, other groupings
are possible such as XXX, XXY, and XYY (Harper, 2007). Many individuals have a
genetic sex that falls outside the binary boundaries of XX and XY (Dreger, 1998),
clearly demonstrating that “genetic sex is not always exclusively binary” (Harper,
2007, p. 168). As noted by Ellis and Eriksen (2002, p. 290), “One in 500 people