Unequal investment: Parental resource allocation between ill and healthy siblings – Preliminary results

Absztrakt

Background: From an evolutionary perspective, parental investment involves allocating limited parental resources among offspring to maximize reproductive success. A child’s illness poses a substantial challenge to family functioning and may alter parental investment strategies; however, empirical findings in this area remain inconsistent. Moreover, healthy siblings of ill children are often overlooked both in research and in everyday parental practice.

Objective: The present study aimed to examine patterns of parental investment in families raising an ill child compared to families with exclusively healthy offspring, from an evolutionary–psychological perspective.

Subjects and methods: The study included 126 Polish families: 63 families raising both an ill and a healthy child and 63 families raising exclusively healthy offspring. Mothers completed an original questionnaire used to construct indices of emotional, financial, and total parental investment, as well as to assess the family’s socioeconomic status.

Results: In families raising both an ill and a healthy child, the ill child received significantly higher emotional (Z=2.43, p<0.05), financial (Z=2.88, p<0.001), and total parental investment (Z=3.45, p<0.001) than the healthy sibling, indicating a reallocation of parental resources toward the offspring with greater needs. As the ill child’s age increased, maternal emotional investment (R=-0.32, p<0.05) as well as parents’ total emotional investment (R=-0.26, p<0.05) declined, leading to a reduction in investment disparities between siblings over time. Additionally, healthy children in families with an ill child received significantly lower financial investment (Z=-2.36, p<0.05) than their peers from families raising only healthy children.

Conclusion: Overall, the results suggest that an ill child reshapes parental investment strategies in line with evolutionary models of adaptive resource allocation, often to the relative disadvantage of healthy siblings.