During the last decade, the study of behavioural endocrinology has gone through a very exciting phase. New technologies have appeared which have allowed us to answer new questions; the present book is a reflection of this progress. In the eariy1970's, the advent of steroid radioimmunoassays (RIA) for the first time permitted measurement of gonadal and adrenal steroids in small aliquots of plasma. It thus became possible to measure these hormones repeatedly in the same animals (Le., to undertake longitudinal studies) and also to assay them in small-sized animals such as the rat or the ring...