I find that my stutter is SUPER responsive to altered auditory feedback (AAF) and the increase in my fluency while using it is mindblowing. But I've read research that shows the effectiveness of AAF/DAF has shown to be different among stutterers whose planum temporale is right vs leftward asymmetry. >A brain scan study examined the planum temporale (PT), an anatomical feature in the auditory temporal brain region. Typically people have a larger PT on the left side of their brains, and smaller PT the right side (leftward asymmetry). A brain scan study found that stutterers' right PT is larger than their left PT (rightward asymmetry).[6] A second study found that stutterers with this abnormal rightward asymmetry had significantly improved fluency with DAF (Delayed Auditory Feedback), but stutterers with the normal leftward asymmetry didn't improve with DAF.[7] The study also found that stutterers with this abnormal rightward asymmetry stuttered more severely than stutterers with the normal leftward asymmetry. So I think it's important to keep in mind that not all stutters are a monolith. For many stutterers, AAF is an effective tool, but for others, it isn't. There's really no practical way of finding out which group you belong to, except to give it a shot. All that said, and even as someone who's had success with AAF, I'd definitely not buy devices like SpeechEasy. There are apps out there that can do this for you, some are even free. It's not worth the money.