their own countries. There has been an increase in the number of older-child adoptions and adoptions from third-world sources in first-world countries. Adoptions and births to same-sex couples have increased in number and gained legal protection, compared to their status in Bowlby's time. Regardless of whether parents are genetically related, adoptive parents attachment roles they will still influence and affect their child's attachment behaviors throughout their lifetime. Issues have been raised to the effect that the dyadic model characteristic of attachment theory cannot address the complexity of real-life social experiences, as infants often have multiple relationships within the family and in child care settings. It is suggested these multiple relationships influence one another reciprocally, at least within a family. Principles of attachment theory have been used to explain adult social behaviours, including mating, social dominance and hierarchical power structures, in-group identification, group coalitions, membership in cults and totalitarian systems and negotiation of reciprocity and justice. Those explanations have been used to design parental care training, and have been particularly successful in the design of child abuse prevention programmes. While a wide variety of studies have upheld the basic tenets of attachment theory, research has been inconclusive as to whether self-reported early attachment and later depression are demonstrably related. Neurobiology of attachment In addition to longitudinal studies, there has been psychophysiological research on the neurobiology of attachment. Research has begun to include neural development, behaviour genetics and temperament concepts. Generally, temperament and attachment constitute separate developmental domains, but aspects of both contribute to a range of interpersonal and intrapersonal developmental outcomes. Some types of temperament may make some individuals susceptible to the stress of unpredictable or hostile relationships with caregivers in the early years. In the absence of available and responsive caregivers it appears that some children are particularly vulnerable to developing attachment disorders. The quality of caregiving received at infancy and childhood directly affects an individual's neurological systems which controls stress regulation. In psychophysiological research on attachment, the two main areas studied have been autonomic responses, such as heart rate or respiration, and the activity of the hypothalamic–pituitary–adrenal axis, a system that is responsible for the body's reaction to stress. Infants' physiological responses have been measured during the Strange Situation procedure looking at individual differences in infant temperament and the extent to which attachment acts as a moderator. Recent studies convey that early attachment relationships become molecularly instilled into the