Psionic Skill

Psi Skill is a rating of the effectiveness with which the soldier can use his inherent psionic ability.

Starting Values

New recruits will always begin with a value between 16 and 24. This is awarded upon completion of first month's Psi Lab training.

Maximum Caps

An X-COM soldier's Psi Skill has a combat increase cap at 100, but can continue to grow past that through Psi Lab training.

Improvement

Psi Skill is increased by use of Psi on the battlefield, and through Psi Lab training. Both successful and unsuccessful psi attempts during combat result in improvement.

Psi Skill will increase from 0 to 6 points per combat mission, depending on how many times you attempt a Psi action (Panic or Mind Control, MC). With one successful psi, an average of 2 points (range 1-3) are awarded. With 4 successes, 4 points (range 2-6) are awarded. No more skill points will be earned, no matter how many more attempts are performed.

The above numbers are for successful Panics or Mind Controls. Failed Psi attempts cause the Psi experience byte to increase by a third as much as successful ones. So Psi failures do help you gain skill points, but at a lower rate. 11 failures (vs. 4 successes) will get you all the potential skill points you can get at the end of the combat mission. For more information, see Soldier Experience.

Because you can get a +6 roll when at cap-1 (99) if you have enough attempts, it is possible to have get a Psi Skill of up to 105 (cap+5) from combat. For more info, see Regarding Caps.

Unlike any other skills, Psi Skill is not truly capped. Although combat increases stop once you reach 100+, the Psi Lab increases skill as follows:

 End of Month  Psi Lab Increase
   Psi Skill    Range  Average
     0-16       16-24   20.0
     17-50      5-12    8.5
     51+        1-3     2.0

It has three distinct stairsteps, and rolls randomly within each range. Rookies always start with 0, and thus get 16-24 skill points in the first month's training. If you got unlucky and only got 16, the next month's training will give you 16-24 again - if you don't earn a single point on the battlefield! That's about five combats' worth of the maximum possible average of 4 points per combat, versus the two combats' worth that the psi lab will give you for psi skill in the 17-50 range... so you might want to not exercise a 16's psi skills at all, if he won't be going on 3+ combat missions in his or her second month (but they can still go on missions and do other actions).

Also notice that Psi Lab training keeps awarding 1-3 points per month way above psi skill 100 - about 24 points/year. It breaks down at 255 because the counter byte wraps around to 0. Of course, it would take over 6 game years to go from 100 to 255, and training can always be turned off then. (Also note: stats at 170+ wrap around on the stat display screen.) Then again, who needs anything over a psi skill of 60 anyway, if their psi strength is 90+?

Note: Psi Lab training is lost (for a given month) if the soldier is transferred to another base, even if the destination base has Psi Lab space available. Especially avoid transferring right before the end of the month, or they'll lose two months' worth.

See Also

Psi Strength