ABSTRACT
Mammalian mothers of different species may differ in the extent to which physiological and psychological factors contribute to the postpartum expression of their nurturant behavior. In all species that have been studied, however, the physiological determinants are only realized in individuals that have had certain developmental histories and that 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. However, whether these nurturant behaviors in fact occur at the appropriate time and in the appropriate way depends on a host of psychological and environmental 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-resourced 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 robust; to eliminate maternal behavior entirely, environmental restrictions or debilitations experienced by mothers have to be extreme and depend on the animal’s background and genetics (Aubert, Goodall, Dantzer, and Gheusi, 1997; Jenkins, McGowan, and Knafo-Noam, 2016; McGuire, Pachon, Butler, and Rasmussen, 1995; Mileva-Seitz, Bakermans-Kranenburg, and van IJzendoorn, 2016; Stolzenberg and Champagne, 2016b). In nonhuman 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 are young and inexperienced, neglected or battered their own (usually first) offspring, despite having apparently normal pregnancies and childbirths (Brett, Humphreys, Fleming, Kraemer, and Drury, 2015; Coe, 1990; Harlow, 1963; Ruppenthal, Arling, Harlow, Sackett, and Suomi, 1976). In human beings, a host of background and psychological factors increases risk of mothering disorders, including poverty, low education, social isolation, lack of supports, and immaturity, being themselves victims of abuse (Agrati and Lonstein, 2016b; Barrett and Fleming, 2011; Britton, 2008; Brummelte and Galea, 2016; Correia and Linhares, 2007; Daly, 1990; Dennis, Heaman, and Vigod, 2012; Di Florio et al., 2013; Eisenberg, 1990; Lancaster, Gold, Flynn, and Yoo, 2010; Lomanowska, Boivin, Hertzman, and Fleming, 2017; Milgrom et al., 2008; O’Hara 31and Swain, 1996; van Bussel, Spitz, and Demyttenaere, 2009; Vesga-López et al., 2008; Viguera et al., 2011) and their genetics (Mileva-Seitz et al., 2016).
