Billy paused, a hand drifting to rest over his new breast.

"Largely sensory information that can't be directly translated," he answered finally, fidgeting a little. "We can describe how certain actions and sensations feel, but...for instance, no act in the world can simulate the experience of having breasts."

Oh yes. He found himself looking down at his, wishing they were a little bigger for research purposes---but hey, he couldn't have everything in life.