Specifically Penile-Vaginal Intercourse Frequency Is Associated With Better Relationship Satisfaction: A Commentary on Hicks, McNulty, Meltzer, and Olson (2016)

In a recent Psychological Science article, Hicks, McNulty, Meltzer, and Olson (2016) asserted that previous research on the association between sexual frequency and relationship satisfaction led to inconclusive results. However, Hicks et al. overlooked good evidence that there is a consistent relationship between penile-vaginal intercourse frequency and measures of relationship satisfaction (among other dimensions of satisfaction and indices of psychological and physical health and function; Brody, 2010; Brody & Costa, 2009; Brody, Costa, Hess, & Weiss, 2011; Costa & Brody, 2007; Maunder, Schoemaker, & Pruessner, 2017; Santtila et al., 2008; Smith, Nezlek, Webster, & Paddock, 2007). Other sexual behaviors (e.g., masturbation, anal sex, cunnilingus) are generally uncorrelated or even adversely associated with relationship satisfaction and other satisfaction measures (Brody, 2010). The significance of the associations between penile-vaginal intercourse and relationship satisfaction remains consistent in studies using large representative population samples or multivariate methods to control for the frequency of all measured sexual behaviors (Brody & Costa, 2009; Santtila et al., 2008). Space limitations preclude presenting a metaanalysis of the correlations between penile-vaginal intercourse frequency and relationship satisfaction, but examples include effect sizes (Cohen’s ds) such as 0.72 for men and 0.63 for women in a nationally representative Swedish sample (N = 2,810; Brody & Costa, 2009), 0.21 for men and 0.32 for women in a Finnish study of twins (N = 3,604; Santtila et al., 2008), and 1.04 for women in a convenience sample from Portugal (N = 30; Costa & Brody, 2007). Unfortunately, many studies fail to differentiate between penile-vaginal intercourse and other sexual behaviors, which thereby precludes the ability to detect essential differences between sexual behaviors. Various studies have found that when sexual behaviors are not very clearly defined, some individuals even exclude certain categories of sexual activities from their definition of sex (Byers, Henderson, & Hobson, 2009; Gute, Eshbaugh, & Wiersma, 2008; Peterson & Muehlenhard, 2007). Hicks et al. noted that in their own study results, there might have been a biasing effect due to not being sufficiently specific regarding definitions of sex. The two studies that Hicks et al. cited as not finding an association between sexual frequency and relationship satisfaction actually measured “any sexual engagement between spouses in which at least one of the spouses experienced an orgasm” (Hurlbert & Apt, 1994, p. 491) and “any mutually voluntary activity that involves genital contact and/or stimulation, even if intercourse or orgasm did not occur” (Heiman et al., 2011, p. 744). It has been noted that sexual pleasure is an evolutionary adaptation that ultimately motivates people to engage in penile-vaginal intercourse in the service of reproduction; however, sexual pleasure can be diverted to other functions, and people can engage in sexual behaviors other than penile-vaginal intercourse for the 691547 PSSXXX10.1177/0956797617691547Brody et al.Penile-Vaginal Intercourse and Relationship Satisfaction research-article2017