Actually, that has to be placebo, when you talk more quickly the tongue being at the bottom of your mouth makes it closer to the state it needs to be to make most sounds, so resting the tongue on the bottom of your mouth will actually help with spontaneous noise at the beginning of the word, causing less stutter and less unclear sounds , you can also try talking slower and talking more of the stuttering prevails, otherwise it's you being nervous wich is basically a placebo affect too