An appropriate intervention is constantly provided for a worker without relying on the experience or the intuition of a manager for improving and enhancing the productivity. Vital sign measurement data and motion measurement data obtained from workers WK1, WK2, and WK3 during operation are used as primary indicators. The primary indicators and learning data generated separately are used to estimate the emotion and the cognition of the worker. The estimated emotion and cognition are used as secondary indicators. The secondary indicators and relational expressions generated separately are used to estimate the productivity of the worker. The variation of the productivity estimate is compared with a threshold that defines the condition for providing an intervention. When the variation of the productivity estimate is determined to exceed the threshold, the intervention is provided for the worker.