They say your body is "wired" to expect sugar when it tastes sweetness. It makes sense to me that the body can respond to anticipation of sugar. After all, Pavlov's dogs didn't have to taste food when they heard the bell....

They did research it, and are careful to say "In some people"... Kind of like how some people can stomach the sugar alcohols, and some can't. IMO, it's a matter of degree.