Age Isn’t Just a Number: How Bones Reveal the Brain

Abstract

Cognitive development during adolescence is shaped by multiple factors, including formal education, life experience, and biological maturation. While the effects of environmental influences are often considered in developmental studies, biological processes such as puberty tend to be underexplored, in part due to reliance on invasive or subjective assessments. In this study, ultrasonic bone age measurement was employed as a non-invasive indicator of biological maturity—referred to as biological age (BA)—to disentangle its effects from chronological age (CA) on adolescent cognitive abilities.

A sample of 117 females was used to assess cognitive domains such as verbal comprehension, working memory, processing speed, and perceptual reasoning. Bone age was measured using an ultrasonic scanner targeting the wrist’s growth zone, which provided a safe, fast, and reliable alternative to traditional X-ray methods. This technique allowed researchers to assess biological maturity independently from calendar age. The primary analysis utilized regression models to identify the distinct contributions of BA and CA to each cognitive domain, thus enabling a more precise understanding of the developmental processes involved.

The findings revealed a dissociation in developmental patterns: verbal comprehension was significantly associated with CA but not BA, indicating the influence of schooling and accumulated knowledge. In contrast, BA significantly predicted performance in working memory and processing speed, which are more closely tied to neurophysiological maturation and structural brain development. These domains are thought to be influenced by pubertal processes such as synaptic pruning and white matter growth. Perceptual reasoning, however, showed no significant relationship with either age metric, suggesting some cognitive abilities may follow a distinct developmental timeline [1].

This study highlights that adolescent cognitive development is heterogeneous across domains and that using only chronological age may obscure meaningful individual differences. These conclusions support the Cattell–Horn–Carroll (CHC) theory of intelligence, which proposes a hierarchical model encompassing a general intelligence factor (g), broad abilities like fluid and crystallized intelligence, and specific cognitive skills. The research validates that fluid abilities (e.g., processing speed) and crystallized abilities (e.g., verbal knowledge) can develop on different timescales and be driven by distinct biological mechanisms.

From an applied perspective, the use of non-invasive bone age assessment provides a valuable tool for research, educational planning, and clinical diagnostics. Understanding whether a child’s cognitive profile aligns more with their biological maturity or their chronological age can inform tailored interventions, school placement decisions, and developmental support strategies that better reflect individual needs rather than age-based expectations alone.

References

[1] I. Kovács et al. “Ultrasonic bone age fractionates cognitive abilities in adolescence,” Scientific Reports, vol. 12, no. 1, p. 5311, Mar. 2022, doi: 10.1038/s41598-022-09329-z.