There are vast individual differences in the ways in which people approach close relationships. Where do these differences come from? According to developmental perspectives, including attachment theory, these differences are rooted in people's interpersonal experiences, starting with their earliest relationships. In the present review we outline alternative models on whether and how early experiences with primary caregivers shape developmental adaptation. We also review recent empirical data which suggests that, at least in some domains, early experiences can leave an enduring mark on psychological development.