Читать книгу Infants and Children in Context - Tara L. Kuther - Страница 237

Smell and taste receptors are functional in the fetus and preferences are well developed at birth (Bloomfield, Alexander, Muelbert, & Beker, 2017). Just hours after birth, newborns display facial expressions signifying disgust in response to odors of ammonia, fish, and other scents that adults find offensive (Steiner, 1979). Within the first days of life, newborns detect and recognize their mother’s odor (Macfarlane, 1975; Marin, Rapisardi, & Tani, 2015). Infants are calmed by their mother’s scent. Newborns who smelled their mother’s odor displayed less agitation during a heel-stick test and cried less afterward than infants presented with unfamiliar odors (Rattaz, Goubet, & Bullinger, 2005). Familiar scents are reinforcing and can reduce stress responses in infants (Goubet, Strasbaugh, & Chesney, 2007; Nishitani et al., 2009; Schaal, 2017). For example, the scent of breast milk can slow heart rate in premature neonates who are under stress (Neshat et al., 2016).

Infants show innate preferences for some tastes (E. S. Ross, 2017). For example, both bottle-fed and breastfed newborns prefer human milk—even milk from strangers—to formula (Marlier & Schaal, 2005). Newborns prefer sugar to other substances, and a small dose of sugar can serve as an anesthetic, distracting newborns from pain (Gradin, Eriksson, Schollin, Holmqvist, & Holstein, 2002). Experience can modify taste preferences, beginning before birth: Fetuses are exposed to flavors in amniotic fluid that influence their preferences after birth (Beauchamp & Mennella, 2011; Forestell, 2016). In one study, the type of formula fed to infants influenced their taste preferences at 4 to 5 years of age (Mennella & Beauchamp, 2002). Infants who were fed milk-based formulas and protein-based formulas were more likely to prefer sour flavors at 4 to 5 years of age compared with infants who were fed soy-based formulas, who, in turn, were more likely to prefer bitter flavors.