Thank you, Colleen. I've replied to the discussion on One or two hearings aids just now. Fascinating stuff to consider and not easy to come up with a definitive answer for! Regarding Bobby's question, it fits that same pattern. Given my background of hearing-in-noise and spatial hearing R&D, I think some things that might be generally under-appreciated are how finely tuned our auditory system is to small time delays and frequency changes, how dependent we are upon hearing well in the 6-10 KHz range, and how the outer ear helps enable our ability to localize and extract target sound sources. Hearing aids in one or both ears slightly (and confusingly) change the timing and frequency information that our hearing has used over a life time of learning (presuming onset of hearing issues in older age) to sort out voices and other sounds. In addition, our ears are not exactly the same - the right one deals with speech better and the left one with noise. (Recall how an average person might lean forward with their hand cupped behind their right ear to hear better in a noisy situation). Finally, I'll toss into this mix the idea that while vision and hearing correction are only very superficially alike, one way that they might be is in how the brain learns to always expect a correction. In the early days of someone new to glasses, the change is a hard one. But, over a few weeks, the brain learns to adapt. The same seems to be generally true with hearing aids. Likewise, with glasses, one might be tempted to use them all of the time (even when not needed, like when viewing things far away when you are far-sighted) or even use higher magnifications even when not needed. This trains the brain in a way that is perhaps not optimal and there are those who argue that it even causes atrophy of muscles and neural pathways that would otherwise be beneficial. I'm not an audiologist nor an optometrist and will very willing accept correction by those who understand these matters more deeply. Very best, Keith