It is whether to attack or play safe.
''I haven't figured it out yet,'' said the Dubliner, fifth at the Masters in April and eighth in the US Open last month.
''I would like to have a good handle psychologically on what I should be thinking before the start. I've looked at past scores like Nick Faldo's 66-64 start here last time and you have to think that's good scoring on this course.
''So what happens if you're plodding along and you're one over after five holes? Do you panic? It's trying to get a grip on the mental approach and it's not easy here.
''That's what is good about the course. I don't know what's going to make a winner win is it superb, consistent golf or is it because he's playing exciting golf, hitting drivers, making birdies?
''You go to a US Open and you know it's patience, patience, patience and all about trying to play the same shot over and over and over again hit the fairways, hit the greens.''
Faldo, as well as setting the lowest 36-hole total in major championship history in 1992, won in 1987 with 18 successive pars in the final round.
''I don't think anybody would take 72 pars in a row this week,'' added Harrington.
Midway through a practice round with Justin Rose yesterday, word reached them of Rose's pairing with Tiger Woods in the first two rounds.
Harrington was in that position in the third round in New York last month.
''With Maruyama in the group as well, Justin's got probably the two most popular people with the cameramen Shigeki will probably have about 30 and Tiger about 50.
''If Justin can enjoy it that will be great. But I think it's going to be more of a learning process.
"Maybe it will inspire him, but I suggest it will actually hinder his chances. There's definitely going to be a distraction there and it will be harder.''