How many Jacks have just 1 eye?

Our friends last night, knowing we have played cards all our life, asked that question. We did not know. Nor did we know how many Kings or Queens look left or right.
Evidence of what we should know: that just seeing something does not mean that we are aware of what it is like. Knowing the one-eyed Jack's never helps in playing bridge or any other card game, so the focus of attention is never on the Jack's eyes.
But focusing narrowly is what makes us poor at Trivial Pursuit.