Excerpt:

"Researchers used to think you had to drink the glucose and get it into your body to give you the energy to [have] self control," says coauthor Leonard Martin, professor of psychology. "After this trial, it seems that glucose stimulates the simple carbohydrate sensors on the tongue." He adds: "This, in turn, signals the motivational centers of the brain where our self-related goals are represented." And it's these signals, he adds, that wake your body up and tell it to start paying attention.

That consuming small amounts of sugar regularly boosts motivation and willpower has been known for a long time, but as the article says the assumption has been that this is due to the actual intake of sugar. What they are saying is that they think their results may show that simply tasting the sugar is sufficient.

(But I wonder if they controlled for whatever amounts of sugar subjects might inadvertently get in them anyway while gargling)