“When golfers are “under par” (e.g., shoot a “birdie” putt that would earn them a score one stroke under par or shoot an “eagle” putt that would earn them a score two strokes under par) they are significantly less accurate than when they attempt otherwise similar putts for par or are “over par”.”
The reason expanded upon in Kahneman’s book is that we are hard wired to worry more about loss than gain, and the performance (or in this case, the putting) gets better when you are trying to avoid failure. This, despite the fact that a birdie putt or a par putt are of equal value and are only differentiated because of the par assigned for the hole.
“Pope and Schweitzer theorized that players would try a little harder when putting for par to avoid a bogey than when putting for a birdie. They analyzed over 2.5 million puts in exquisite detail to test that prediction. They were right. Whether the putt was easy or hard, every distance from the hole, players were more successful putting for par than for a birdie.
The difference in the rate of success when going for par to avoid a bogey or for a birdie was 3.6 percent. This difference is not trivial. Tiger Woods was one of the participants in their study. If in his best years, Tiger Woods would have managed to putt as well for birdies as he did for par, his average tournament score would have improved by one stroke and his earnings by almost $1 million per season.”