Human functioning emerges from the relationship between the person and the environment.

That is why the same individual can appear highly capable in one context and overwhelmed in another without either observation being false. The demands changed. The supports changed. The consequences changed. The person’s current state changed. Or the environment stopped fitting the way their capacities are organized.

Fit should not be mistaken for comfort. A demanding environment can be developmentally productive when challenge is survivable and feedback is usable. An apparently easy environment can also suppress development if it removes every opportunity to practice needed capacities. The question is the relation between demand, support, capacity and adaptation over time.

Person–environment interaction is well established in rehabilitation and occupational science. PEOP’s core proposition is transactional: person, environment and occupation jointly shape performance and participation. The initiative can build on that science by asking whether the fit can be expressed in terms of domain-specific capacity requirements and supports.