Del Giudice's target article addresses a complex and pertinent theoretical issue: the evolutionary adaptiveness of sex differences in attachment styles as they relate to life-history strategy. This is an extremely important theoretical problem in evolutionary psychology, and we applaud Del Giudice for bringing it to the attention of the field; but we are not convinced that the present article makes a very substantial contribution to its resolution. Although the theory seems plausible, Del Giudice does not make the necessary theoretical connections to sufficiently integrate these two constructs.

One major limitation is that Del Giudice mentions certain important issues that are critically relevant to the topic, but rather than explaining them or taking a position on them, he claims that they are beyond the scope of the article. For example, he does not address whether or not attachment patterns are categorical or continuous, and instead references the work of Fraley and Spiker. Del Giudice must take a stand on this issue if he is going to take an evolutionary stance on attachment patterns based on individual differences – in our understanding, specifically in the direction of the patterns being continuous. He also does not fully address the degree of persistence versus plasticity of “internal working models” across the life cycle, stating that “a detailed treatment of the issue is beyond the scope of this article” (sect. 2.3, para. 1). Without explaining these issues in more detail, the conclusions seem based more on belief than on a principled deliberation on the evidence.

Aside from the lack of explanation, Del Giudice also makes contradictory statements without offering a resolution. For example, Del Giudice discusses the affect of increasing age on life history trade-offs, with aging men switching from mating effort to parental investment. He argues that “this transition may be especially dramatic in insecurely attached men” (sect. 7.1.3, para. 3). However, prior to this he discusses a couple of studies finding that “short-term mating in men tended to increase with age, and men were on average more oriented with short-term mating regardless of attachment style” (sect. 6.4.1, para. 2). This is an apparent contradiction that is left unresolved.

Del Giudice also discusses “disorganized” attachment style early in the article, stating later that it will not be integrated into his synthesis on account of three concerns about the concept. However, in the very next paragraph he mentions it again, arguing that it is the only infant attachment pattern showing a sex difference. If one of the main points of this article is to discuss theoretical reasons for sex differences in attachment, this issue may be of critical importance. Granted, Del Giudice suggests that this is an important area of research for the future, but because he has written this BBS target article specifically on the topic of evolutionary perspectives on sex differences, he needs to offer his perspective on why that one notable infant sex difference may exist.

One might argue, for example, that an infant's attachment style has a different function than an attachment style displayed during adolescence or young adulthood. At each point in time, the goals and relationship of the child with their parent differ, and so we would expect attachment styles to vary as well. The attachment style towards romantic partners, friends, and other members of society would also require a different relationship, and possibly a different style of attachment. It seems that at each developmental stage, one would want or need different things from the relationship, so the same attachment style might not always be appropriate.

On the other hand, there are also reasons to expect some degree of stability in attachment styles over time. For example, Del Giudice addresses genetic influences on attachment styles during the course of development, but fails to properly discuss genetic predispositions (e.g., temperament) of the child which might be present at birth, thus setting a baseline on which to build during development. Del Giudice partially addresses the stability of attachment style over time, but does not suggest which factors might differentially influence those individuals who do and who do not have stable attachment styles over time, given the probable existence of such predispositions.

As Del Giudice is aware, our laboratory has published multivariate models of latent life-history constructs that support the cross-situational consistency of attachment styles across both childhood attachment to parents and adult attachment to romantic partners (Figueredo et al. Reference Figueredo, Vásquez, Brumbach and Schneider2004; Reference Figueredo, Vásquez, Brumbach, Schneider, Sefcek, Tal, Hill, Wenner and Jacobs2006; Reference Figueredo, Vásquez, Brumbach and Schneider2007). This latent variable has been shown to have a high heritability coefficient (h ²=.65) and is probably a good candidate both for early childhood predispositions that shape later developments and an individual difference variable that predicts temporal stability versus instability in attachment styles over time. Although Del Giudice cites this work, he does not pursue its implications for the resolution of this theoretical problem.

There are also various miscellaneous concerns to which we would have liked Del Giudice to respond. For example, we disagree with the statement (in sect. 3.1, para. 2) where Del Giudice writes, “In order to be selected for, traits need to solve two problems: being adaptive at the present time and being adaptive in the future of the organism.” Selection has nothing to do with the future of the individual organism. It has to do with what worked in the ancestral past (teleonomy). Does the author understand this principle, or is this just a very poorly worded sentence?

We are also confused by Del Giudice's analysis of polygyny and attachment. We can understand how the arguments apply to serial polygyny, where the father ends one relationship and moves on to another one, potentially decreasing the resources invested in the previous family. However, we do not understand how this relates to societies with simultaneous polygyny, where the father will continue to invest in previous wives/families, even if it is only through material resources rather than bioenergetic ones.

Despite our criticism of the target article, we do feel that it is important to make the issue of evolutionary bases for sex differences known to a wider audience. However, in its present execution, the article seems to be lacking in ability to resolve some of the key issues concerning this topic.