There is mixed support for similarity in same-sex couples. Kurdek’s early study found that there was very little similarity in gay couples, except for age. On the other hand, a later study devised by Kurdek (2003) found that partners within gay and lesbian couples were similar in terms of age, education and income. His study had high validity as issues of participant variability were overcome by the use of well-matched partners. However couples were lost from the sample every year and this attrition might have biased the sample, for example they were destined to breakup before the study was conducted. Furthermore the study was predominantly white and well-educated so therefore is unrepresentative of diversity within gay and lesbian community.
Kurdek & Schmitt (1986) measured love of partners and liking of partners in married couples, heterosexual cohabiting couples and gay and lesbian couples. The level of love in all four couples was high, and did not differ significantly between them. The level of liking was also similar in all four groups, but it was somewhat lower for heterosexual cohabiting couples than for the other three. However there are many issues with this research method. There could be issues of social desirability whereby they may lie and give a false answer to be seen in a positive light. Moreover this cannot be generalised to arranged marriages as is focuses on specific relationships.
Blumstein and Schwartz (1983) found that 48% of lesbians and 36% of gay couples broke up within two years of being interviewed, compared with 29% of heterosexual cohabiters and 14% married couples. However in Gottmans et al