"Egos would get the better of Ireland; they'd try and play a different way and be more expansive. They sometimes did (change) to their detriment. Look at England, (defence coach) John Mitchell came out and said before the first game of the Six Nations and said 'We can't let Ireland bore us to death'.
"I think Ireland tried a few things and realised 'we know what works for us'. But the thing with Ireland, when we had our success against Ireland, we went in thinking discipline was really important, stopping that go-forward from No 9, and then if you did that what do they have to go to?"
Gatland also suggested it was too easy to get under the skin of then-Irish coach Joe Schmidt, who stood down from the role after the World Cup.
Gatland told Off the Ball that Schmidt seemed to get more wound up ahead of a test against Gatland's Welsh squad, because anything Gatland said "drives him crazy."
"It does bother Joe. He might deny that, but people within the Irish camp are telling me: 'Please don't say anything this week, because Joe will go mental about any comments you make'."