Independent play, the capacity to play alone, self-direct, and sustain engagement, is one of the most valuable developmental capacities of early childhood.
Self-directed, independent play is the primary context in which executive function develops. When a child plays alone, they must generate their own goals, sustain their own attention, regulate their own frustration, and maintain their own motivation, without external prompting. This internal management of experience is precisely what the prefrontal cortex is built for, and precisely what it needs to practise.
Key citation
Gray, P. (2013). Free to Learn. Basic Books · Diamond, A. (2013). Executive Functions. Annual Review of Psychology
Britain's oldest toy maker. Every toy open-ended, wooden, and built for exactly the kind of play the research recommends.