health consequences. This was also published as Child Care and the Growth of Love for public consumption. The central proposition was influential but highly controversial. At the time there was limited empirical data and no comprehensive theory to account for such a conclusion. Nevertheless, Bowlby's theory sparked considerable interest in the nature of early relationships, giving a strong impetus to, (in the words of Mary Ainsworth), a "great body of research" in an extremely difficult, complex area. Bowlby's work (and Robertson's films) caused a virtual revolution in a hospital visiting by parents, hospital provision for children's play, educational and social needs, and the use of residential nurseries. Over time, orphanages were abandoned in favour of foster care or family-style homes in most developed countries. Bowlby's work about parental provisions after child birth implicates that maternal deprivation negatively influences the attachment behavior trajectory of a child's life. If a mother experiences post-partum anxiety, stress, or depression, the attachment they have with their child can be disrupted. It is important for pregnant women to have mental-health support pre and post-partum because mental illness often results in low feelings of attachment to their infant. Formulation of the theory Following the publication of Maternal Care and Mental Health, Bowlby sought new understanding from the fields of evolutionary biology, ethology, developmental psychology, cognitive science and control systems theory. He formulated the innovative proposition that mechanisms underlying an infant's emotional tie to the caregiver(s) emerged as a result of evolutionary pressure. He set out to develop a theory of motivation and behaviour control built on science rather than Freud's psychic energy model. Bowlby argued that with attachment theory he had made good the "deficiencies of the data and the lack of theory to link alleged cause and effect" of Maternal Care and Mental Health. Ethology Bowlby's attention was drawn to ethology in the early 1950s when he read Konrad Lorenz's work. Other important influences were ethologists Nikolaas Tinbergen and Robert Hinde. Bowlby subsequently collaborated with Hinde. In 1953 Bowlby stated "the time is ripe for a unification of psychoanalytic concepts with those of ethology, and to pursue the rich vein of research which this union suggests." Konrad Lorenz had examined the phenomenon of "imprinting", a behaviour characteristic of some birds and mammals which involves rapid learning of recognition by the young, of a conspecific or comparable object. After recognition comes a tendency to follow. Certain types