Cognitive skills rely on a complex dynamic between biological propensities and experience. We adopt a constructivist neo-Piagetian theory of cognitive development to model paradigmatically and investigate how participants’ executive processes, indexed by latency during correct performance, are functionally affected by their mental-attentional capacity. This capacity or mental-attentional power is a maturational component of working memory, estimated with tasks that parametrically vary the levels of mental-attentional demand. Participants (N = 257 children, 7-16 years old, and N = 226 adults, 19-30 years old) completed three tasks: two colour-matching tasks (CMTs) and one number-matching task (NMT). Results demonstrated a significant interaction between effects due to mental-attentional demand, interference level, and executive
power. With growing age latencies change from ages 13 to 15 or greater, and remain stable for tasks with a mental-attentional demand beyond 6, suggesting that in simple tasks executive power functions independently from task difficulty. Theoretically, the current findings provide support for common and distinct components of executive efficiency and mental attention. Practically, the results point to the trade-off between mental-attentional capacity of the individual and mental-attentional demand of the task, showcasing that measures of mental-attention can serve as tools for further study of relations between executive efficiency and cognitive abilities.