ABSTRACT
Mammalian mothers of different species may differ in the extent to which physiological or psychological factors contribute to the postpartum expression of their nurturant behavior. In all species that have been studied, however, the physiological determinants are realized only in individuals who have had certain developmental histories and who are psychologically “prepared” by their physical and psychological environments (Rosenblatt and Snowdon, 1996). In many mammalian species, the hormonal changes associated with late pregnancy and parturition predispose the newly parturient female to be nurturant with her offspring, to nurse, clean, and protect them (see Rosenblatt, in Vol. 2 of this Handbook). However, whether these nurturant behaviors in fact occur at the appropriate time and in the appropriate way depends on a host of psychological factors. Enhanced morbidity or mortality of young or reduced responsiveness by mammalian mothers occurs if mothers are stressed during pregnancy or parturition, severely food deprived, or are placed in low-resource environments (Lyons, Kim, Schatzberg, and Levine, 1998), if ambient temperature precipitously rises, if pups are sickly, or if the nesting area is inadequate (Herskin, Jensen, and Thodberg, 1998; Kinsley, 1990; Leon, Coopersmith, Beasley, and Sullivan, 1990). However, mothers are also quite robust; to eliminate maternal behavior entirely, environmental restrictions or debilitations experienced by mothers have to be quite extreme (Aubert, Goodall, Dantzer, and Gheusi, 1997; McQuire, Pachon, Butler, and Rasmussen, 1995). In sheep, the specific odor characteristics of the young, as well as the mother sheep’s earliest postpartum experiences, also determine whether hormone-induced responsiveness is expressed in nurturance and maternal behavior or in rejection (Le´vy, Kendrick, Keverne, Proter, and Romeyer, 1996; Poindron and Le´vy, 1990). In primates, examples of the importance of interactive influences of early experiences and hormones on mothering are still more pronounced. Harlow’s “motherless” monkeys, raised in social isolation and on wire mothers or monkeys who were young and inexperienced, neglected or battered their own (usually first) offspring, despite having apparently
normal pregnancies and childbirths (Coe, 1990; Harlow, 1963; Ruppenthal, Arling, Harlow, Sackett, and Suomi, 1976). In human beings, a host of background and psychological factors increase risk of mothering disorders, including poverty, low education, social isolation, lack of supports, immaturity, and being themselves victims of abuse (Moore and Brooks-Gunn, in Vol. 3 of this Handbook; Cochran and Niego, in Vol. 4 of this Handbook; Daly, 1990; Eisenberg, 1990; Magnuson and Duncan, in Vol. 4 of this Handbook).
