A Washington State University-led study has shown that adding water to whisky can enhance its aroma, but beyond 20%, the whisky's flavor and aroma can become indistinguishable from each other. The addition of water leads to changes in volatile compounds that are attracted to water, and those that are repelled by it. Dilution affects what's in the "headspace," or the area above the liquid. American bourbons were mostly associated with vanilla and oak scents at first, but as more water was added, they took on more aromas of corn and grains.