This......and I am a newb to bass from 6 string guitar that mainly plays bass with a pick.You are not going to get any abuse from me for resting your thumb on the pick up. It is all the same to me what method you use. There is no "right" or "wrong" method. There is however, a safe method. Unfortunately resting the thumb on the pick up is generally accepted not to be it. With this method the wrist is at a severe angle. When you move your fingers, the tendons have to pass through the carpel tunnel. Having the wrist angled causes a kind of friction between them because the tunnel is narrowed, kind of like cutting a piece of twine by rubbing it backwards and forwards over a sharp edge. After many years using this technique, injury can occur. With the method that your helpful.... student gave you, i.e. resting the thumb on the strings, the wrist is straight, therefore minimizing the risk of injury from constant use. IMO the only thing your student is guilty of is the label he attached to your technique. Instead of "wrong"..."potentially unsafe" might have been a better choice.
So the "do what feels right" concept is OK up to a point. Problem is that what feels right now, has the potential to have you visiting the doctor or physiotherapist after prolonged use.
IMO it would have been more admirable if first, you had checked out the validity of your student's suggestion before dissing it...and him.
Fifty years playing or not.....you are never too old to learn something new.
The "thumb on pickup" hurts like crazy for me at 55 years of age and dealing with arthritis.
I mute with the left hand AND right hand palm too.
Anchoring the "thumb on pickup" never made sense to me....but to those who make it their style and it doesn't damage them....that's great!
I feel comfortable holding a pick with index & thumb but also the same index & thumb position but NO pick.
