As part of a new and intriguing line of research in behavioral medicine, researchers gave mice saccharine-fl avored water and followed it up with an injection of a drug that weakens mice’s immune systems. Later, when these mice drank saccharine-fl avored water, they showed signs of weakened immune response. Research is currently under way to see if the reverse is possible (if conditioning can be used to increase immune functioning), a discovery that would surely have important implications for new medical treatments. In this experiment, what is the saccharine-fl avored water?