How does music affect plant growth? to answer this question, dr. Anderson set up an experimental chamber and exposed a group of 15 bean plants to the same 60-minute rock cd twice a day, at 9:00 a. M. And 9:00 p. M. Another group of 15 bean plants was placed in a different chamber with the same temperature, light, and humidity, but these plants weren't exposed to music. One month later, the heights and masses of all 30 plants were measured and compared. In this example, what's the responding variable?.