Stuttering is analagous to bad hearing or bad vision. Some have slightly defective vision/hearing and some have very defective vision/hearing and everything in between, Stuttering is the same. Some are moderate stutterers and some (like myself) are severe stutterers and everything in between. I also stutter when alone. I also use the Edinburgh Masker (EM) and it has really helped my speech. However when I do not use the EM my speech is as bad as ever. The important thing to know is that stuttering is basically a physical neurological problem and not a psychological problem.