campboy, on 2015-February-13, 04:13, said:
Well, it doesn't satisfy 73F unless East "could have known" -- if the change of line was truly irrational, how could he have foreseen it?
I think a lot of players know they won't get away with a real pause with xx, so there's some mileage in cultivating a just-perceptible hitch with this holding to sow some doubt in declarer's mind. If there's a significant card out, there's a chance declarer might fall for it.
There are plenty of bridge players who don't decide in advance whether or not to cover an honour. On this hand, the thought process "he's led ♠9 - shall I cover? - no, it can't help" might take a second or two.
So a slight hitch would suggest a holding including the queen.