Del Giudice presents a meaningful extension of evolutionary models of attachment. The target article builds on existing theory to account for the adaptive consequences of various attachment strategies beyond early childhood relationships with caregivers. The central tenet of this body of theory is that attachment functions as a mechanism for adaptively adjusting human life histories and reproductive strategies to the socio-ecological environment in which children grow up. Del Giudice's major contribution is to focus the issue of sex differences in attachment processes through the lens of sexual selection theory. This provides a cogent interpretation of the different relationships between attachment processes and behavioural and life history outcomes in males and females. It also brings into sharper relief the relatively neglected but vital socio-developmental processes occurring in middle childhood. These are theoretical steps forward, and ones that are consistent with the data reviewed by Del Giudice. The major challenge now is to develop and test a range of more critical empirical predictions.
We propose one particular set of predictions for future research. The hypothesized link between attachment and adaptive variation in reproductive strategies (e.g., mating vs. parenting effort) implies that sexual relationships should be a key area for study. Much evidence suggests that women's sexual strategies correlate with mate preferences on certain dimensions of physical attractiveness, such as male facial and vocal masculinity (Gangestad & Simpson Reference Gangestad and Simpson2000; Gangestad & Thornhill Reference Gangestad and Thornhill2008; Provost et al. Reference Provost, Troje and Quinsey2008). In combination with the arguments of the target article, this leads to the prediction that attachment styles should correlate with females' preference for masculine faces and voices. In populations characterized by low paternal investment and high levels of aggressive male–male competition, there is a significantly stronger average preference among females for masculinized facial features than in populations characterized by higher paternal investment (Penton-Voak et al. Reference Penton-Voak, Jacobson and Trivers2004). The evolutionary logic is that, where there is low paternal investment, women's mate choices should be more strongly biased towards males of high competitive ability. Similarly, women seeking short-term sexual relationships have a stronger preference for masculine features than those seeking long-term relationships (Little et al. Reference Little, Jones, Penton-Voak, Burt and Perrett2002), again indicating a link between likelihood of paternal investment and preference for masculinity. The theoretical link to attachment processes is that female dismissiveness should correlate positively with masculinity preferences. On the other side of the coin, males with more masculine faces tend to have more sexual partners and be less interested in long-term relationships (Boothroyd et al. Reference Boothroyd, Jones, Burt, DeBruine and Perrett2008). Consequently, facial masculinity should correlate with attachment profiles in males.
Sexual strategies also vary according to the individual's perception of their own “market value” (Little & Mannion Reference Little and Mannion2006). An intriguing corollary of the target article is that these perceptions may correlate not only with physical attractiveness, but also with the experience of attachment relationships in middle childhood. This would predict an association between attachment profile and self-rated attractiveness.
Finally, female sexual strategies have been shown to be hormonally influenced. During the menstrual cycle, women become more interested in short-term relationships, are more likely to be unfaithful to their long-term partner, and are more attracted to masculine facial and vocal features around the time of ovulation, when the risk of conception is high (Penton-Voak et al. Reference Penton-Voak, Perrett, Castles, Kobayashi, Burt, Murray and Minamisawa1999; Feinberg et al. Reference Feinberg, Jones, Law-Smith, Moore, DeBruine, Cornwell, Hillier and Perrett2006; Gangestad & Thornhill Reference Gangestad and Thornhill2008). This has been interpreted as reflecting a “dual” sexual strategy, promoting mating with competitive but low-investing males while also garnering paternal investment via a long-term relationship. A further prediction is therefore that attachment profiles should vary cyclically, directly mirroring the cyclicity in sexual behaviour. This would imply that attachment profiles, albeit perhaps largely fixed early in life, also have some previously unsuspected adaptive plasticity.
