Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford

Age of Child

  • Prarthana FranklinEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_2303-1



The developmental age of child that is associated with the highest parental investment.


The age of a child is shown to have important effects on parental investment decisions. This is likely because the age of the child may be associated with the child’s ability to survive (Volk et al. 2005; Hrdy 1999). For example, newborns are less likely to survive without parental care compared to older children due to lower levels of health-related development at that stage (e.g., less developed immune systems; Voora et al. 1982) and higher dependency on parental care compared to older children (Hrdy 1999; Volk and Atkinson 2008). Therefore, the offspring that shows the highest chance of survival, which is generally the older child, should typically receive the most parental investment as this child will more likely produce offspring and help propagate parents’ genes (Trivers 1972). However, this would suggest that parent may be predisposed to make parental investment decisions more strongly based on parents’ own interests of propagating their genes rather than the child’s interest. On the other hand, younger infants are certainly more in need of parental care for survival compared to older children (Hrdy 1999; Volk and Atkinson 2008). Therefore, it could also be hypothesized that parents may be predisposed to make parental investment decisions based on what is best for the child. If this is the case, then parents’ investment decisions could be perceived to be more strongly dependent on children’s interests rather than parents’ immediate (evolutionary) interests. So who do parents actually invest in: younger or older children?

A close look at the data on parental investment based on age of the child suggests that parental investment decisions may be more complex than any of the above two theories would independently suggest. Franklin and Volk (2017) helped shed some light on this when they proposed an inverted “U” curve associated with child age and parenting decisions. This is based on evidence which suggests that adults may have the strongest caregiving predispositions toward children between 3 and 6 months old, which represents the peak of the inverted “U” curve (Franklin and Volk 2017; Franklin et al. 2018). The bottom left of the curve represents adults’ least positive perceptions and caregiving behaviors toward newborns. This is presumably in part because the newborn stage is associated with the highest mortality rates across childhood and therefore may be the riskiest age for parental investment (Volk and Atkinson 2008). Finally, the bottom right of the curve suggests that adults’ perceptions and caregiving behaviors tend to slightly reduce after 6 month stage (Franklin and Volk 2017).

The reason for adults’ apparent peak in caregiving perceptions and behaviors at 3–6 months is likely because this is the stage at which there may be an optimal balance between children’s robust health and need/dependency on parental care (Franklin and Volk 2017; Franklin et al. 2018). For example, compared to newborns, 3 and 6 month olds are more likely to survive illnesses and infections without serious medical intervention (Voora et al. 1982). Additionally, older children can more independently survive without parental care. Therefore parents may not ultimately evolutionarily benefit from investing in older infants at the expense of younger infants (Franklin et al. 2018). Therefore, investment in infants between 3- and 6-month-olds appears to be the safest investment that still allows parents to ensure infant survival without depleting too much of parents resources.


The underlying factors that are suggested to influence the peak in parental investment toward children between 3- and 6-month-old infant strengthen the idea that in cases of conflict between parents’ and children’s interests, evolutionary pressures may have favored parents’ interests over those of children (Trivers 1974). More specific to parental investment based on child’s age, it appears that parents may be predisposed to invest in offspring at an age at which the offspring will optimize parental parents’ resources. Therefore, the age of the child may be an important factor to consider when trying to understand the complexity associated with caregiving decisions.



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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Child and Youth StudiesBrock UniversitySt. CatharinesCanada

Section editors and affiliations

  • Kevin M. Kniffin
    • 1
  1. 1.Cornell UniversityIthacaUSA