Correcting the Vertical Axis Perception Error

Posted by : Tom Simpson

I am a left-handed player and I am having difficulty with slight angle cut shots, 45 degrees or less. For some reason on shots from the left to right I calculate my contact point and then my aim point, but my aim point has to be further right than you would think. If I don’t do that, I will overcut it. Why does this happen? I have my own table and have tried everything to figure this out. Angle shots from right to left are pretty much normal. I don’t know any other way to explain this. It’s just very weird how full my aim point is on shots from left to right.

George E.

A: NOTE: This question was asked by a lefty, but the answer applies to both left-handed and right-handed shooters.

Frustrating problem and one that 80% of the players that show up at my pool school have.  Almost none of them are aware of it!  Many players have more trouble with “back cuts,” cutting toward a pocket that’s not quite in sight. But if I understand your description correctly, this sounds like a bigger issue. Without actually seeing you set up and shoot, here’s my best guess at what’s happening.

It’s a perception and setup issue that I call the Vertical Axis Perception Error. It is caused when your eyes are not correctly aligned above the shot line so that your brain can accurately see the center of the cueball. We refer to the correct alignment location as your Vision Center and it can be different for each player. For some players, it’s under an eye. For others, it’s elsewhere. To correct this, we have to identify your personal Vision Center and get it over the stick.

Let’s look at the symptoms first. Among players with this issue, right-handers usually hit the left side of the vertical axis of the cueball and it looks to them like they are hitting center. Left-handers hit the right side. We trust our eyes and that we’re lined up to the shots as we see them, but maybe we’re just not seeing them correctly. If we aren’t hitting the cueball on the vertical axis, it will be hard to trust your aim because of squirt and throw effects.

Squirt occurs when you do not hit the vertical axis of the ball. If you strike even slightly to the right side of the ball, for example, it will head off on a line that’s a few degrees to the left of the stick line. It will also have right spin, in this example. Also, the farther away the object ball, the more squirt, and the worse the miss.

Sometimes, putting a little spin on the cueball will help correct the shot through the spin-induced throw effect. For example, if you apply a little left spin on the cueball, the cueball can pull the object ball angle a few degrees to the right, which sometimes cancels out the squirt error.  Speed is also be a factor because if you hit softly, the spin will have more time to curve the cueball back toward the stick line. This is part of why sometimes the shot will work and sometimes it won’t. Speed and spin can mitigate the squirt error.

Correcting Vertical Axis Perception Error:

I identify and correct this issue on every player I work with. For those who have played a long time, it’s particularly frustrating that they are so inconsistent. You have to get your eyes in the correct place for your brain to able to accurately see where the cueball’s vertical axis truly is. This means moving your head to a slightly different location above the stick.

Everyone is different, so I can’t tell you exactly what to do here. In person, we’d work through a few head adjustments and identify which one corrects you perfectly. Since we’re working in print, I’ll offer the simplest adjustment for you to try on your own – head height.

Set up the cueball near one end of the table and an object ball near the other end, more or less in a straight line up and down the table. Go down on the shot, lining up your stick dead center through both balls. Stop with your tip near the cueball when you believe you have the alignment. You’ll need to have someone stand at the far end of the table so they can see if your tip is centered on both balls. I expect they will tell you your tip is somewhere to the side of the vertical axis of the cueball which you will probably find hard to believe.

Head height is the first and easiest adjustment to try. If you are a player whose head is very low (we refer to those players chin-draggers), try bringing it up a few inches. Set up centered on the straight shot again, viewing it from your new, experimental head height. Have your friend at the other end of the table confirm that you actually changed your head position and tell you whether your tip position has changed. Conversely, if you are a more upright player, try bringing your head down a few more inches toward the stick.

For many players, this is all it takes. If it’s more complicated than this, let’s talk pool school, where this stuff becomes very clear, and we “get your head in the right place." Send me an email at and I’ll send you info about my National Billiard Academy Weekend Intensives, offered in 12 cities.

Good luck to you!