Mother–Infant Relationships in Baboons (Papio hamadryas): Predictors of Differences and Discontinuities in Developmental Pathways Marı ´a Victoria Herna ´ndez-Lloreda and Fernando Colmenares Universidad Complutense de Madrid This study uses hierarchical linear regression modeling to analyze sources of variation in the develop- mental pathways of mother–infant relationships and to search for behavioral discontinuities. The data come from 23 mother–infant dyads of baboons (Papio hamadryas), whose interactions were recorded longitudinally during the infants’ 1st year of life. The infant’s sex and the mother’s age and reproductive experience accounted for part of the variation observed in the developmental pathways of 11 of 20 behavioral measures analyzed; however, some of them did so only in some periods but not in others. The authors proposed that this can reflect the occurrence of reorganizations or discontinuities in the mother–infant relationship that can be related to important life events such as the mother’s resumption of sexual activity. Motherhood in primates is very costly indeed, both in terms of time and energy invested, and is unusually prolonged in time, as primate development is such a slow process (Altmann, 1983; Kappeler, Pereira, & van Schaik, 2003; Martin, 1990; Nash & Wheeler, 1982; Nicolson, 1987, 1991; Pereira & Fairbanks, 1993). In effect, primate infants need and use their mothers as sources of nutrition, warmth, transportation, stimulation, contact comfort, and protection from inclement weather, predators and threatening con- specifics (Fairbanks, 2003; Hrdy, 1999; Nash & Wheeler, 1982; Nicolson, 1991; Pereira & Altmann, 1985). In this respect, primate mothers are the central figures of their developing infant’s early ontogenetic niche (cf. West & King, 1987) and their main input (see also Alberts & Cramer, 1988). It should be further emphasized that early primate mother–infant relationships are not only critical for infant survival in the short term, but their quality at this early stage may have long-term consequences for the infant’s behavioral and social competence later on (i.e., juvenescence, adolescence, and adulthood; Suomi, 1989, 1995, 1997; Suomi, Novak, & Well, 1996) and, ultimately, for their reproductive success (Collinge, 1991; Fairbanks, 1996). In fact, the physiological and psycholog- ical mechanisms that regulate the individuals’ behavior at all ontogenetic stages are strongly influenced by the nature of this very early relationship (Kraemer, 1992; Suomi, 1989, 1995; see also Hofer, 1987). Moreover, the nature of their relationship may in turn influence the mother’s reproductive success (Berman, Ras- mussen, & Suomi, 1993; Fairbanks, 1996; Nicolson, 1982, 1987; Simpson, Simpson, Hooley, & Zunz, 1981). Mother–infant relationships among primates are highly variable both within and between species (Fairbanks, 1996, 2003; Mae- stripieri, 1994, 2001; Nash & Wheeler, 1982; Nicolson, 1987, 1991; Schino, D’Amato, & Troisi, 1995). The variables most commonly analyzed to account for this variation have to do both with characteristics of the relationship partners, for example, the sex of the infant and the age, parity, reproductive experience, and dominance rank of the mother (Berman, 1984; Fairbanks, 1996; Nash & Wheeler, 1982; Nicolson, 1987, 1991; Schino et al., 1995), and with characteristics of the developing mother–infant dyad’s social milieu and ecological setting (Altmann, 1980; Berman, 1984, 1988; Berman, Rasmussen, & Suomi, 1997; Maestripieri, 1998; Rosenblum & Paully, 1984; Simpson, 1988). Although it is clear that both dimensions should be expected to interact with one another at varying extents, the impact of this interaction effect is as yet poorly understood. In fact, the study of the effects of each of these variables and of its interactions has often yielded inconsistent results across studies within and between species (e.g., Berman, 1984; Fairbanks, 1996; Nash & Wheeler, 1982; Nicolson, 1987; Schino et al., 1995). In regard to studies of baboons (Papio spp.), Altmann found that the best predictor of individual differences in mothering style was the mother’s dominance status (Altmann, 1978, 1980; Altmann & Samuels, 1992). She found no effect of infant sex or mother age. In contrast, Nicolson (1982) reported no effect of maternal rank on the weaning process; she found, however, that the mother’s age did influence her maternal style and that the infant’s sex accounted for differences in infant carrying. By contrast, Rhine, Norton, and Marı ´a Victoria Herna ´ndez-Lloreda, Departamento de Metodologı ´a de las Ciencias del Comportamiento, Facultad de Psicologı ´a, Universidad Complutense de Madrid, Campus de Somosaguas, Madrid, Spain; Fer- nando Colmenares, Departamento de Psicobiologı ´a, Facultad de Psicolo- gı ´a, Universidad Complutense de Madrid, Campus de Somosaguas. This work was partly supported by a postdoctoral fellowship from the Spanish Ministry of Education and Culture to Fernando Colmenares (1988 –1991) and by project grants PB98-0773 (1999 –2001) and BSO2002-00161 (2002–2005) from the Spanish Ministry of Science and Technology to Fernando Colmenares. We thank the students that partici- pated in the data collection and in the tabulation: S. Albares, M. J. Blanco, R. Gil, and C. Moratalla, and M. J. Cepero, M. M. Esteban, V. Gutie ´rrez- Diego, M. Pertegal, and F. Zaragoza, respectively. We also thank Rosario Martı ´nez-Arias for statistical advice. We are grateful to the staff of the Madrid Zoo for their cooperation in the maintenance of the baboon long- term research project. Correspondence concerning this article should be addressed to Marı ´a Victoria Herna ´ndez-Lloreda, Departamento de Metodologı ´a de las Cien- cias del Comportamiento, Facultad de Psicologı ´a, Universidad Com- plutense de Madrid, Campus de Somosaguas, 28223 Madrid, Spain, or to Fernando Colmenares, Departamento de Psicobiologı ´a, Universidad Com- plutense de Madrid, Campus de Somosaguas, 28223 Madrid, Spain. E- mail: vhlloreda@psi.ucm.es or colmenares@psi.ucm.es Journal of Comparative Psychology Copyright 2005 by the American Psychological Association 2005, Vol. 119, No. 3, 311–324 0735-7036/05/$12.00 DOI: 10.1037/0735-7036.119.3.311 311