>>243923from what i've read it works with blacks and with grizzlies but only rarely.
regardless of the type of bear, you need to know if it's being defensive of predatory. if it's just afraid of you and being defensive against you playing dead *may* help, in that it has subdued you/you are no longer a thread and it just wants to get away from you
if it's predatory playing dead is just laying your meat out on a platter from which it will snack at leisure
as a general rule, if you aren't 100% sure what the bear has in mind fight for your life