Thigmotropic stamens are sensitive to the touch. If you put your finger in a flower, the stamens lean over and touch your finger, much like a sea anemone does when you poke your finger inside.
In the same way the filaments contract when touched by a bee or other pollinator and move toward the centre of the flowers, this happens very quickly. Thigmotropism may be a strategy to force pollen on to the bodies of pollinators to assist in cross pollination.
Examlpe of thigmotropic stamens can be foun in many plants belonging to different family (Portulacaceae, Cactaceae, Aizoaceae, and Tiliaceae Cistaceae Helianthemum Stylidiaceae etc.)