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Psi Combat Formula

Just had a thought on the formula!

What if the "Psionic Combat Strength" formula was a ' + ' rather than a ' * ' ?

It would mean the example Soldier would have a PCS of 111, rather than 1520, and the defending Muton would have:

Panic Chance = 76%
   MC Chance = 56%

These numbers seem more reasonable, don't you think?

--Danial 15:32, 19 Nov 2005 (PST)

Right, it sounds much more reasonable now. My actual results were 1192 successes out of 2420 tries = 49.26% success rate. The MCer was right next to MC victim, and we know distance introduces some kind of decrease to base chance. That's the good news. The bad news is that I also tested psi str 95, skill 44 (and some higher skill levels) and never failed to MC once with these better MCers. Using your revision, a psi str 95, skill 44 guy should have had a success rate of 84% vs. a beginner Muton soldier (psi str 25, skill 0), not 100%. My higher-skill guys were also right next to their MC victims. So, to me the first example makes sense relative to your idea (fits base chance, plus a little distance adds a little more), but the second example counters it.
Still, it sounds WAY better than 1500% :)
I sure wish psi testing wasn't so labor intensive. I got those 2400 counts doing all that experience testing... not interested in doing it again, just for psi equations. At least not at the moment. :P ---MikeTheRed 21:12, 23 Nov 2005 (PST)

Sectopod Psionic Resistance

Question: why is the Sectopod's psionic resistance listed as N/A? I've mind-controlled sectopods (or at least one square of a sectopod) on many occasions. I usually have it shoot itself, since it can target one of its other, non-MC'ed squares. From my anecdotal experience, their psi resistance seems somewhat high. --Papa Legba 14:19, 2 February 2006 (PST)

Answer: If you look on the alien summaries in the wiki they all have a PSI resistance listed, except the Sectopod. Since it's not listed anyplace I put N/A. Feel free to put it where it belongs in the list if you have enough experience to feel comfortable ranking it. --Darksun
Darksun, I took the liberty of signing your name for you, and making a separator line. Why not say a word about yourself under User:Darksun and also, use four dashes (----) to demarcate entries. For more on the basics of wiki'ing, see NKF's "Community Portal" at the bottom of the homepage. Past all that - welcome, fellow XCOMMIE! We were all wiki noobs once. But not everybody loves XCOM. You must. Welcome aboard!
Proceeding right along to flagellating, laugh - Where are you folks talking about Sectopod psi resistance being "N/A"? I see their Psi Strength as 100, and their Psi Skill as 0 at Beginner; Psi Strenth 116 and Skill still 0 at Superhuman. In this respect, they match Cyberdisks. What do you folks mean by Psi "resistance"? Do you know the math behind the psi equations? I haven't been able to figure it out. But the stats I just listed are ones hacked out of the game... Zombie is going to present a full precis' some time soon.
Great speaking at ya ... keep on contributing, Darksun!! --MikeTheRed

Alien psionic resistance

I haven't tried mind-controlling Cyberdiscs much, but if, as I've read elsewhere, both Sectopods and Cyberdiscs have have a Psi Strength of 100, they should probably both be classed "extremely high". --Ethereal Cereal 10:30, 4 May 2006 (PDT)

Psionic testing

I started doing some testing to figure out the psionics formula.

Initial finding: distance takes the hypotenuse into account. I'm not sure if the actual Pythagorean formula is used, but I can say this much: an Ethereal was able to panic a moderately-psi-weak soldier at 30 squares along the horizontal but not at 30 squares along the diagonal.

Second finding: the difference in "difficulty" between MC and panic is definitely 20 points (although that may not be percent). A soldier with 97 Psi strength, 0 Psi skill standing adjacent to an Ethereal Leader (60 str/45 skill) could not be panicked at all, but 96 Psi str could (often). The same soldier with 77 Psi str couldn't be mind-controlled, but could at 76 Psi str. With further testing, I see that 60/45 vs. 97 should succeed occasionally; I might retest this for greater precision, although the +20 still seems to hold.

Third finding: A soldier with 99 Psi str/0 skill could just barely be panicked by an adjacent Ethereal with 63/45. I couldn't count how often the Ethereal succeeded, but it was something like 1%-2% of the time. The same soldier was panicked just as infrequently by an Ethereal with 45/63 (str & skill reversed), and much more often by an Ethereal with 54/54. This pretty strongly suggests the attack portion of the formula involves psi str & skill multiplied together.

Data points collected so far:

  • Ethereal, 63/45, just barely panicked soldier, 99/0
  • Ethereal 40/40 just barely panicked soldier 75/0
  • Ethereal 27/27 (multiplied together = 729) just barely panicked soldier 57/0
  • Ethereal 10/73 (multiplied = 730) just barely panicked soldier 57/0
    • this confirms that attacking is based on str*skill
  • Ethereal 18/18 just barely panicked soldier 49/0
  • Ethereal 1/1 just barely panicked soldier 43/0
  • Ethereal 1/1 just barely panicked soldier 1/210
    • this confirms Psi skill / 5 is used in calculating defense; 1 + (210/5) = 43

I also tested Ethereal 0/1 (no psi str, 1 pt. skill); it still attacked, but did not attack at 0 pts. skill no matter how high psi str was (no surprise there, otherwise all units would do psi attacks).

I ran the points through a curve-fitting program and got a nice and simple answer:

attack strength = psi str * psi skill / 50
defense strength = psi str + (psi skill / 5)
Panic Attack chance = 44% + attack strength - defense strength
Mind Control Attack chance = 24% + attack strength - defense strength

The formula has held up under limited further testing; I'm satisfied it's correct. I invite others to test it more than I have.

The impact of distance has yet to be tested, but it should be easy to figure out now.

--Ethereal Cereal 22:03, 26 May 2006 (PDT)

There is a reasonable approximation to the Pythagorean formula (in the plane) that could have been used, that doesn't require loops or floating-point math:
max( | Δx | , | Δy | ) + ½min( | Δx | , | Δy | )
where Δ_ := _2 - _1.
It overestimates slightly. I haven't thought through how this would generalize to 3D. [Yanked from Moria, Angband, and variants...think it's too basic to copyright, though.]
One way to test whether the distance estimator is no greater than true Pythagorean formula by working out the greatest distance (pure x or pure y) that MC/Panic is not 0%, then testing on a diagonal with a "computed same". An integer-math overestimator (like the above) would by 0%.
Muliple of 5 allows replacing the diagonal with a suitably scaled 3-4-5 triangle...should work as well for testing.
--Zaimoni 2:38PM, 26 May 2006 (CDT)

Wow... good approach to teasing this out, Ethereal!
Am I doing this right? I plugged in numbers for Muton, 25/0, Me 95/44, and got 83% MC Base Chance... But in much repeated testing (when learning about experience counters) it seemed quite solid that I was MC'ing him about half the time. Say 45-55% of the time. This was when right next to each other. Is 83% right for your equations?
Zaimoni, re: your equation, see Explosions#Distance_from_Ground_Zero. XCOM seems to use a fairly simple approach that doesn't involve Pythagoras per se. Since it's based on a very old engine, much of its stuff is integer based. Cool deal on the deltas and other wiki symbols - I wish I knew about them sooner! Actually I know where wiki symbol tables are... just didn't bother to look up so many symbols. :P
Nobody has tackled 3D distance yet, but I may soon, in studying illumination.
Once the equations are well known (maybe they are already), I imagine some cool 3D topographical graphs of the various factors (skill and strength, you vs. enemy) could be made. Do either of you have surface graph s/w at hand? All I've got at the moment is Excel. :(
Great work! Also thanks for cleaning up the page in general, Eth.
---MikeTheRed 22:24, 2 June 2006 (PDT)

I suspect you've misremembered the details of your tests. The 49.26% success rate out of 2400 trials that you quote above would have been for your 95/16 soldier doing panics, not MCs: 44 + [95*16/50 = 30.4] - 25 = 49.4%, almost exactly the same as your 49.26%. A 95/44 doing panics would always succeed: 102.6%. A 95/44 doing MCs would succeed 82.6% of the time.

--Ethereal Cereal 11:06, 3 June 2006 (PDT)

Ah, there's that data. Thanks for reminding me. I can't remember what I put in which discussions and was going to dig it out of my db.
No, it was MCs. Indeed I relied on the lack of seeing an enemy, if I got moving too fast and couldn't remember if I successfully MC'd. Attention starts to wander with such highly repetitive testing. This was before I realized the following...
Anyone doing repetitive psi testing can readily and accurately get the number of positive results from the UNITREF.DAT Psi byte [84] if you work it right. Note the turn you start psi attempts. Then do exactly 2 or 3 psi Attempts each turn, as your TUs allow. Then note the turn you stop and get the delta. Turns x Attempts/Turn = Attempts. A failed psi attempt adds 1 to [84] and a successful attempt adds 3, so the number of successes is: ([84]-Attempts)/2. Be careful during testing marathons because the byte wraps around at 255 (=85 straight successes, or 28.3 turns at 3 successful attempts per turn). Then it starts counting again so actually even this can be dealt with by adding 255 if you're on top of it. If anybody wants an applet that shows Unitref experience values on the fly, let me know. It's great for building experience. Right now it's embedded within my mdb though... I'd have to tease it out.
I'm using XCOM DOS which I once ran XcomUtil on, if that matters.
---MikeTheRed 12:21, 3 June 2006 (PDT)

Distance...ok, no reason for the game to use multiple 2-d distance formulæ.
I have software set up to render 3D graphs. Is there anything on the site that jumps out as "would like to see first"? I'd rather wait until the psi formulæ are calibrated first before graphing those.
Ethereal: What I see posted is test data for ethereal MC human. Do you have test data for human MC ethereal as well? [That would test whether the game calculations are symmetrical.]
---Zaimoni 2:37, 3 June 2006 (EDT)

It is possible X-COM units get a different formula from aliens -- I only tested an alien doing psi, as it was more automated -- the thing would psi without my having to control it.

I'm not not volunteering to test x-com units for the time being -- it's a bit more laborious -- but if I had to test it, I'd do a small number of trials of 35/16, 50/51, and 100/51 soldiers trying to MC (not panic) an adjacent Muton, which should succeed 10.2%, 50% and 101% of the time.

Feel free to test it before I do. ;-P

Oh, and nice work on the flares, Mike.

--Ethereal Cereal 12:50, 3 June 2006 (PDT)

Sounds cool, Zaimoni... As for "like to see",
Once my troops have psi ability, I try to get 90+ psi strength guys. Then the question becomes "at psi str 90, at what psi skill point are most/all aliens certain to be MC'ed?" In my experience, it's somewhere around skill 40-60... Anything that might show this, or show how you fare relative to aliens at, say, STR 90, is something I've always wanted. However it might be done. In one sense you could simply plug the "worst" psi alien (Ethereal CDR?) into Eth's equations to get the final answer. But it'd be good to see the lay of the land.
If you make the simplifying assumption that many of your targets are psi skill 0, there's one less variable. Additional graphs can be done later just for the psi-capable aliens... first things first though...
Taking the above into consideration, then, XCOM Psi Skill (Str=90) vs. Alien Psi Strength (Skill=0) vs. Success rate is one 3D graph that could be made. If you can do a 4th dimension as color, you could replace the Success rate axis with XCOM Psi Str, then have color indicate success rate, from primary red for "no way" through yellow for "sometimes" to primary green for "always". Or something like that. It'd also be nice but not critical to have annotations for where various aliens lie along their dimension. I can supply this info if you want. Which reminds me: Eth, Zombie and others found some errors in Aztec's table (which came from the OSG). Just a few percent of them, but they're definitely there (I can't remember where). I've hacked alien stats straight out of GEOSCAPE... see the alien stats page. I believe Zombie has found these to be correct, but he has not yet given the final word.
Zai, as far as I'm concerned, you can model using EC's equation already, if you have the time... I'm sure his equations are very close, if not spot on, and even if not, it may show key places to test and otherwise support further testing. E.g., both aliens and XCOM can readily have their relevant values hacked to test for boundary conditions of 0% and 100% success. Plus once it's set up it shouldn't be hard to tweak the equation and voila, the graphs update. But if you don't have the time - eh, it's all volunteer work anyway.
Eth, I suppose it's possible aliens vs. humans is different. They are known to have some differences in functionality, such as night vision. I don't know if I'll be able to test, but it definitely intrigues me. BTW I said somewhere else that I was looking into automating the XCOM interface in order to do psi testing. I have concluded that I can't do it. At least not the way I was hoping to. Oh well. Still, my belated realization that one can use Unitref[84] to count psi successes is a real boon to repetitive testing. So we'll see. Thanks for suggestions on what to test if I do. By the way, did I do that 83% correct? I just want to make sure I'm doing the math right.
Thanks re: the flares!
---MikeTheRed 21:08, 3 June 2006 (PDT)

The influence of distance still needs to be tested, although it doesn't seem to be an enormous factor. Rather than a complicated graph, I think a few charts with distance = 1, 10 and 20 would probably tell the story more clearly. The distance formula might even prove to be something really simple, like +1 distance = -1% chance.
The hardest aliens to MC are Sectopods and Cyberdiscs: look at the Psionics#Summary_of_Alien_Psionic_Resistance section I added. At distance 1 on Superhuman you'll need 93 to 192 Attack Strength to achieve 1% to 100% chance. Assuming Psi Str 90, that's Skill 52 to 107.
Now vs. the strongest attacker: Superhuman Ethereal Commander, attack str 88. You'll need a Resistance of 132 to be totally immune to panics from one adjacent to you -- that's str 100, skill 160, or str 90, skill 210. Against MC, it's str 100/skill 60 or str 90/skill 110. In practice you won't be right next to them, so you can probably go a bit lower. They'll focus on the weakest soldiers anyhow, which in practice means a couple of decoys in with some supertroopers is a good strategy.
82.6%, yes.
--Ethereal Cereal 21:51, 3 June 2006 (PDT) is CPU-bound when converting the graph from 2D to 3D. [XCOM Psi Str/Sk 90/0-107, alien Psi Str/Sk 25-116/0; I'm on a 1GHz Pentium III/512MB] Not sure how ColdFusion single-IP demo would do yet (would have to reinstall), but the UI options look better in

I'll attempt the transition later today (when I know I'll be away from the system and positively not working). I just need to be able to take a screenshot.

You probably already noticed this: even if a bug permitted a 0 Psi Skill operative to use a Psi Amp, the success chance of MC is still negative.

Also (thinking about the testing anomaly MikeTheRed had): The floating-point change in success rate from an increase of 1 in Psi Skill is 1.9 at 95 Psi Str. Integer truncation would make this 1...leaving the floating-point formula overestimating by 39.6%. At the precision of reporting, this works.

[Edit: but does *not* work against the initial regression. So, no good.]

---Zaimoni 9:51, 4 June 2006 (CDT)

Got a chance to run the bar graph this go, doesn't like a horde of data points on both axes.

But...this particular graph is essentially a plane. It should be hand-drawable, even if the more complicated ones aren't.

---Zaimoni 8:35, 5 June 2006 (CDT)

Hi Zaimoni... I'm not sure I understand the differences you talk about. You mean you can get your s/w to make a graph where you've specified the points by hand? Anyway, if you take a shot at most anything, we'd be able to give feedback... a picture's worth a thousand words. Thanks for working on it! ---MikeTheRed 06:36, 5 June 2006 (PDT)
Somewhat. Layer 1 of the spreadsheet is the raw data to be graphed (took about five minutes to set up). If I was going to commit to this representation, I'd go back and make the XCOM Psi Str and Alien Psi Skill configurable. So it's trying to graph data points (the MC success chances) on 0-107 by 25-116. I was planning to rotate the view after getting the initial graph up on Layer 2. [Time loading is not favorable for working further on this today.]'s autoscaling isn't compensating properly. I haven't checked how to suppress the "color key" that was auto-generated for Alien Psi Str — it's not leaving enough space for the vertical bars to even be 1 pixel in size. The result is decidedly flat, with "correct" vertical range.
As a bar graph, I could get away with subsampling (but don't have a clean way to do it). Yes, it should be possible to correctly graph this (as a plane in three-dimensional space) with only four data points: the corners.
---Zaimoni 12:39, 7 June 2006 (CDT)

Psychic Farm

There's a sort of tactic I use which may fit into this article. It's blatant simple: building a base with a couple Living Quarters and as many Psionic Laboratories as possible, hire the entire population of a small town and get them into psionic training. There may be a pre-selection for soldiers with appalling stats. I don't know what happens to veterans, but in my games by the time I get Psionic Labs money is not a constraint anymore, so I find this industrial breeding quite viable. What do the savvy say about this?--Trotsky 02:40, 11 July 2006 (PDT)

Hiya Trotsky,

That's what I do. You might want to see my info on recruit statistics and Hiring/firing (esp. the last bullet under General Info). If you get the full 1,000 recruits per month, about 50 will have psi strength of 95+. Taking other stats into consideration, one or two dozen will be top-notch recruits.

I only have 2 or 3 actual combat squads. One of my less-busy bases serves as initial receiving for batches of ~100 (no psi labs needed), and other un-busy bases get the recruits who made the initial cut farmed out to them, for psi evaluation (lots of psi labs needed).

FWIW I have an applet that reads a savegame; I run it when a new batch of recruits shows up, and it prints out who to keep based on a prioritization. It's ordered by base and soldier names at that base so I go directly to Sell/Sack and dump the ones that didn't cut it, without needing to look at their stats in the game. Then those guys move on to your "psychic farm" bases for psi evaluation. Before I wrote the applet, I would stick a little plus sign next to the names of the guys to keep as I reviewed them in the Soldier Stats screen, so I'd know who to Sack.

Because you can only have 250 soldiers max, and some are devoted to combat or other duties, depending on how you draw the line on initial recruit stats (and how hard you want to work at it), plus the fact that psi results only come up at the end of the month and you need to have the next batch on hand for next month's evaluation... this all means that there's actually only ~100 noobs undergoing psi evaluation on any given month. Also, the number of new recruits you order in batches goes down from the beginning of the month to its end, since you only have a window of ~100 to work with initially. At least, that's how it works for me.

If I run a game a long time, over time what happens is that the bar for psi strength in my 2-3 active combat crews rises over time. Each month, the few high-psi recruits push a few vets below the bar. The best of these vets are farmed out to lesser bases, in case of attack. Of course, any of us could've won long before this point; we're playing just for the joy of play.

Despite all the above, if a soldier has good psi strength, almost anybody can become a superman, given enough combat. The difference between the worst recruit and the best is only about a dozen combats (assuming they can get 3 actions for firing and reaction each combat).

---MikeTheRed 16:14, 11 July 2006 (PDT)

I see people creating scripts and stuff to analyse the game files to know who to sack, psi training hundreds of soldiers to finally only keep 2 or 3 guys... All of this is time consuming at best. Why don't you just hex-edit the games file to improve the soldiers? Or hack the game to always show the psi strength, or generate only ubersoldiers? Yeah this would be cheating. But screening 1000 soldiers a month... Seb76 03:20, 25 May 2008 (PDT)

Suggestions for Psi Defence

The first aim on missions is to pick off as many aliens as possible without them sighting you. With luck you can break their morale before you get a single psi-attack. Once a soldier is seen the aliens will often, but not always, pick off your weakest soldiers mercilesly (I've had a soldier with 83 strenth panicked as the sole attack during a mission, strangely). The second aim is to get your vulnerable soldiers disarmed so they can soak up all the psi-attacks harmlessly. You can do this by getting soldiers to drop everything when they return to your control, making sure weapons are stored on the ground instead of in hand, or stunning and reviving soldiers. Killing a soldier under alien control will only result result in another soldier being targetted. As you can't keep all your soldiers harmless all the time you should use all available cover to make sure that your troops cannot see each other. This reduces the damage if a soldier gets controlled. Don't use explosive weapons. Don't hold primed grenades between turns. Don't use proximity grenades close to your troops and clear any when soldiers panic in their direction.

Once a mission is completed you can rename the soldiers to record their Psi capability. I'd stick an X on their name, say, for poor defence. Soldiers which look like they have good Psi strength can be marked for training. Soldiers with poor defence will be no use in Cydonia so they can be sacked, used as scouts, or used as decoys on later Psi missions.

On Psi-attack, I think it's worth mentioning that if you stun an alien while it is under mind control then it will not be captured at the end of the mission. I have lost a commander this way.

- Egor


Is this how you add your 2cents? I've been playing xcom since PS1. I loved it but hated the load time on it. The PC version was faster but somehow not as good. Anyway, I've found the most successful preventive tactic vs psionics is to not bunch your troops together. If an alien sees you and you don't kill it that turn, it's a sure bet someone will be controlled. (someone may be controlled anyway but it cuts the result by at least half) I've played the game so much the tactical aspect is predicable (so easy) for me except when you have powerful psionics against you so I started to send out 2-3 man squads (spaced apart) toward the target and the rest of my squad spread to the 4 corners of the map. As troops die you send in one or two more troops. I've found that I hardly recieve psionic attacks when I approach the enemy this way.


This is a cheat. On Psionic farming. Create a univeristy base devoted to psionics, say 100 students. Forward the game by not attacking and ignoring everything. See the results of the troops and copy down their names. Restart a day later and expell all "failures" and hire the amount of students equal to vacant spaces. Repeat as often as you have (time) no life for. lol I've found the cpu registers the psionic power/skill when the charcter is created and not when the month is up. I've had 37 characters with 100 ps str this way in 3 game months. (it took 5 hours off my life though...)

You might want to use colons : to indent your paragraphs. Putting a space in front of it is the shortcut for preformatted text - and that has a tendency to look unpleasant depending on your screen settings. Also you can sign your posts by entering four tildes ~~~~ rather than head it with your username.
When a new recruit is hired, psi skill is set to 0, while psi strength is a random roll from 0 to 100. So yes, the strength level is predetermined the moment the soldier is hired. The game only reveals the psi strenth stat when the psi skill stat is greater than 0, which is where the first month in the labs comes in.
With a bit of code diving, we've confirmed the 20 turn grace period and the 2-remaining alien condition before psionics are launched. But have we done so with the visual aspect of it? -NKF 02:01, 25 May 2008 (PDT)
NKF: No, seems I somewhat jumped the gun on that one. For what it's worth, I've noticed that the AI gets smarter after about turn 20(what with the noted leaving of the UFO and stalking of your units) as well as a smart AI when only a handful of aliens survived the crash. (This may well be why I've had the lone alien from the small scout ambush my troops on more than one occassion; he knows where they are at all times.) Just my theories. Arrow Quivershaft 03:24, 25 May 2008 (PDT)
The code dig was not related to psi attacks in particular. The game sets the visibility flag to 1 for all XCOM units in the 2 cases you mentionned, no more no less. Seb76 03:42, 25 May 2008 (PDT)
Edit: I did a quick check: the game does not seem to test the visibility flag when searching for a target! If you patch offset 0x469B in the CE edition from 0x02 to 0x03, it _might_ test for it. Feel free to test... Seb76 03:57, 25 May 2008 (PDT)

First of all, I'm a new player, and I've found this website indescribably helpful. Thanks a lot! I have a question about psionics. I'm playing the Steam version, and psionics is not turning out to be the game-breakingly-powerful weapon I've heard it described as. I can never seem to MC more than 1 alien 1 time during a mission. Even a Psi Strength 99 soldier can't grab Sectoid Solders with any reliability. I chalked it up to lack of skill, but find that 1 of the first half-dozen attempts for a single battle works great, and then it never works again. And I have NEVER seen any of my soldiers gain increased Psi Skill, though apparently it's supposed to go up like crazy. I've observed the same phenomenon in TFTD. Am I doing something wrong? I assumed MC was incredibly unreliable, but I don't even bother to use what's supposedly the most powerful ability in the game. And man, I could use it in TFTD right now, that game is rough...

Thanks a lot, I really appreciate the time you guys put into this.

--wfames 2:38, 19 Jan 2009 (EST)

Hiya wfames, welcome to the UFOpaedia! Any and all questions or contributions welcomed.
It sounds like something is definitely wrong. Please see Experience#Primary_Stats. Even if every Psi attempt fails (MC or Panic), if you try at least 11 times with any one soldier, that soldier's Psi Skill must go up by 2-6 (average 4) per combat. And a successful attempt counts as 3 tries, so you only need 4 successes to have Psi Skill go up by 2-6. But you're not seeing this? This could be a major problem, if Steam is providing a broken game (and maybe GamersGate too - wouldn't be surprised if they're both selling the same package).
A problem with the half-dozen of us diehards here (although we pray for many more) is that we have a ton of editors, utilities, and X-COM variations tied into our existing X-COM stuff. So we're hoping, of course, that the new bundles are "same old stuff, no problem". If they're not, it's a can of worms ... we'd have to buy something we already own (perhaps multiple copies of), put it somewhere new, test it out for days or weeks. So this is a black news post you made (or at least, it sounds like one). But hey, we're here to help. :)
If you don't mind, pop over to GEOSCAPE.EXE#X-COM_Complete_Packages and make a new "review". Also use the Talk page link there. For the moment, it will probably be better to have any problems or questions in one place (to see if others have the same questions or problems)... later we can diffuse them out to the wiki in general, once we get a feel for whether there are real problems we can nail down and/or easy fixes, etc.
Thanks again for dropping by. Please come back any time! -MikeTheRed 03:58, 19 January 2009 (CST)
What psi skill levels have the soldiers got? Even if their strength levels are high but if the skill levels are low then you won't be getting very frequent successes. You'll want to put several missions worth of psi attempts under your belt before you can really start to hammer the aliens with the good stuff. If you've got a handy alien base nearby, you can send a team of psi troopers there, panic the first alien you see to bits, dust off, check your stats and then repeat the process over and over until you are good enough to use mind control. I recommend the panic attack as it has the highest success probability of the two attacks, and you can have everyone panic the same alien in a single turn - which can't be done with mind control if it succeeds. -NKF 22:55, 19 January 2009 (CST)
Good point, NKF. I assumed he'd played a lot, but should have asked. wfames, are you getting Psi to work yet? Your soldiers' Psi skill will increase ~4 points for every combat, if they make at least 11 unsuccessful or 4 successful Psi actions per combat (the Mind Probe doesn't count). See some cool numbers I generated for a solid handle on when you should be MCing aliens relative to Psi Skill. -MikeTheRed 18:31, 23 January 2009 (CST)

Possibly buggy tactics

2 tactics that may or may not lead to glitches are:

1) Stunning the mind controlled soldier.

2) RE- Mind controlling the mind controlled soldier.

Both of these tactics have unconfirmed rumors of resulting in permanent mind control by the aliens.

How a tiny bunch of human civilians beat the aliens at Psionics

Much as I enjoy getting my *ss kicked in X-COM and thus "losing my favourite game", I sympathise with the aliens because they know exactly how I feel. After all the aliens invented Psionics, millions of years ago, built their society around it, presumably optimised their genome as well since they are masters of DNA, and we come along with no prior knowledge and no genetic mastery and hand them their 'nads, using their own pride and joy, Psionics, in a few short months. While a similar point could be made about plasma weapons and UFOs, this astounding fact still begs a little explanation.

A similarly perplexing question is why X-COM, first and last line of defence of planet Earth, has extremely low field manpower, both initially and long term, and is staffed exclusively with rookies who appear to have no prior combat experience. Surely the world's most powerful governments would be only too willing to put at least some of their elite special forces at the disposal of X-COM - in their own self interest of course? But if you look at the skill gain curves of X-COM operatives, it's clear that these are true rookies. There is nothing odd going in during the Alien Wars that would explain massively accelerated skill growth for already-expert special operations forces (except in the Psi area of course). We have to conclude that X-COM rookies are exactly that, rookies, maybe with basic training but no more. And their initial ranks reflect that.

Here is a non-canonical background suggestion that ties these two anomalies together neatly. Posit this: initial responses to the alien threat, national forces such as the Kiryu-kai, drew heavily on national military special forces. Initial contact with aliens was a total disaster, massively counterproductive, due to alien use of Psionics. Even without overt use of Psionics against them, military operatives in the field against aliens were overcome by Psionic 'noise', panicking and berserking. Their resistance to direct attack was effectively nil in almost all cases. Hence the advanced military skills of these first extraterrestrial defence units were turned against them, causing grievous destruction in the teams, and perhaps worse. (Perhaps in one or more instances, entire teams of heavily armed mind-controlled elite commandos were flying low, under radar, heading directly for the Kremlin or Diet or White House, and were only stopped by the drastic intervention of air force units).

The secret knowledge of aliens possessed by some of the CFN governments significantly pre-dates what XCOM troops on the ground would later learn. Knowledge of the aliens and their psionic potential was a closely held secret within need-to-know groups like MJ-12 in the United States for decades prior to the First War. Analysis of the initial tactical failures suggested that defensive psionic screening was a priority by far outweighing any combat ability or military discipline. As a pre-requisite, the entire field force of X-COM would need to be assembled from individuals who had at least basic Psionic resistance. In these days the idea of Psi Lab screening was at best a hypothesis. However, decades of investigations by MJ-12, in the years after Roswell, had identified a genetic component to Psi resistance. A relatively simple DNA test could identify a tiny proportion of the human population who had the potential, at least, to resist alien Psionics - to varying degrees which could not be further tested except under field conditions. But at a minimum, the DNA test selected the very rare individuals who who not succumb to 'ambient' Psionic fields and would at least require a directed attack by an alien. Perhaps genetic testing of the few special forces soldiers who had put up any resistance helped to confirm the validity of the DNA screening. It turns out the distribution of the rare resistant individuals cut across race and gender, but did to a surprising extent reflect the major players in the CFN and even the apparent major target regions of the alien incursion itself. These very rare individuals, who overwhelmingly were untrained civilians, were inducted into X-COM and rushed through basic military training as quickly as they could be identified.

Putting this in the context of the later mythos evolved in X-COM Apocalypse: What if all X-COM operatives in the First and Second Alien Wars are secretly a type of human-sectoid hybrid? Unknown to themselves and all but a few others in the highest reaches of the XCOM hierarchy, or possibly entirely unknown to human governments, who believe these individuals are just rare human mutants. In fact, a plausible explanation would be that a rebel Sectoid faction, identifying potential with the human DNA at least for the perpetuation of the barren Sectoid species, and perhaps for a new biological weapon to throw off the yoke of the Ethereals once and for all, began introducing Psi-capability genes into human DNA from the earliest contacts - Roswell or earlier.

Whether the decision to recruit exclusively from hybrids was known to X-COM or the CFN at the time of the First or Second Wars, by the time of Apocalypse, the presence of hybrids in the population was well known and such an openly racist recruitment policy could not be pursued. And of course in the time of Apocalypse we see that 'pure' humans are weak or at very best mediocre Psi operators, and that it is X-COM's hybrids who excel - provided of course they are equipped with artificial psi amplifiers to compensate for what is presumably a deficit of raw psi energy, but no deficit of will or talent once the energy problem is artificially solved. All of which simply suggests that Psi Amps may have been a technological 'plant' by rebel Sectoids or hybrids working within X-COM, secretly assisting.

All pure speculation of course. In fact, anyone considering such things is clearly delusional, a danger to society, and should be confined for the safety of themselves and others. Come this way sir, please don't make a fuss, it will be much easier if you just... look... into... my... MIND...

Spike 12:05, 23 October 2012 (EDT)

I am reminded by this of the Saga of the Exiles/Galactic Milieu Trilogy, by Julian May. The premise is that humanity is new on the scene in the galaxy, which is controlled by a confederation of five psychically-active species called the Galactic Milieu. It turns out that humanity evolved psychic powers much faster than any of the aliens, and ends up beating them at their own game. The secret is that Earth was colonised by the Tanu, a psychically-active alien race, during the Pliocene, and the Tanu ended up interbreeding with humanity as it emerged (being responsible for legends of fairies in the process).

The problem with the "secretly Sectoid hybrids" theory (which otherwise works, thanks to TFTD's fluff) is that we see what hybrids look like in Apocalypse, and your psi-soldiers don't look like that in UFO or TFTD.

Humanity being comparable to Sectoids in psionic ability is somewhat explainable. The Sectoids were explicitly on Earth to loot human genes, so it's plausible that one of the traits they're trying to steal was psi-strength. The conclusion there is that the human-Sectoid hybrids in Apocalypse are actually better at psionics than either of their progenitors (hybrid vigour). Regarding the Ethereals, things are a bit tougher. The only explanations I can see would be a) that their powers are mostly expended in keeping themselves alive, and/or b) that the hive-mind society of the aliens blunts psionics.

The real conundrums that don't appear to have any explanation whatsoever besides "UFO fluffed its game design" are: a) If Psi-Amps help, and aliens obviously have the technology to build them, why don't the psionic aliens have them? b) Why are psionics weaker in Apocalypse than in UFO?

If I were remaking X-Com, I'd massively lower the chances of psi working (maybe by making the attack strength divisor 100 instead of 50), and compensate by giving the Ethereals fuckoff-huge Psi-Strength and Psi Skill stats (so they would have similar chances to MC you as in the base game, but X-Com psionics would be unable to mind-control Ethereals or robots). Maybe some of that would come from the Ethereals' kit; I dunno (maybe they're built into the cloaks?). Then I'd diversify psionics along the same lines as in Apocalypse, and make each have a certain requirement of Psi Skill to use: first you'd have "scan" (which would replace Mind Probes) at Psi Skill 1 (or 0, if you wanted to let psi-locked soldiers do it), then "panic" at 20 or so, then "stun" (deals stun damage equal to the amount it rolled over the threshold) at 50 or so, then "control" at 80 or so, then "slay" (deals lethal damage equal to the amount it rolled over the threshold) at 110 or something. Only Ethereal Commanders, perhaps the Brain, and soldiers who'd been maxed out and then trained on top of that would get "slay". The chance of working, however, would go scan >> stun > panic >> slay > control (since a "stun" or "slay" that only barely succeeds doesn't do much). Magic9mushroom (talk) 04:58, 2 June 2015 (EDT)

Psionic Formulas

(Note: I have moved this section here from the original article for preservation purposes. I plan to update the formula so the description will need to be revised. NKF (talk) 03:28, 2 June 2015 (EDT) )

The equations governing psionics are as follows:

 Attack Strength (AS) = INT( Psi Strength * Psi Skill / 50 )        Attacker stats
Defense Strength (DS) = INT( Psi Strength + ( Psi Skill / 5 ) )     Defender stats

  Attack Success (A%) = 100/56 * ( Constant + AS - DS - Distance )

             Constant = 25 for Mind Control
                        45 for Panic

Attack Chance (A%) is a number (0 to 100), not an actual percent (0.00 to 1.00). Values less than 0 mean guaranteed failure, and greater than 100 mean guaranteed success.

It's quite significant that Attack Strength is geometric... a soldier with 100 Psi Strength and 100 Psi skill is not 100 or 200 times better than a soldier with 1 Psi Strength and Skill... he is 10,000 times more powerful at Psi attacks.

These formulas differ slightly from the ones that appear in the Official Strategy Guide, but have been discovered through testing and are believed to be correct.

The further away a target is from its attacker, the lower the chance an attack will succeed. Distance follows the "walking TUs" method, where a distance 10 tiles directly lateral equals 10 in the equation, but diagonal distances are more. For example, 10 tiles away on a pure diagonal is considered to be 15 tiles away; see this for more on Walking TUs distance. The distance factor means that beyond a certain point, aliens can only panic certain units, not mind-control them.

Overall, it's clear that Psionic Strength plays the greatest factor in defense, and that Panic Attacks are more likely to succeed. (a flat 36% higher chance than MC) But Mind Control is much more... useful. Overall, it is probably best to attempt panic attacks when the chances of MC are below 5% ... it can be argued that 8 successful panic attacks are better than 1 successful MC... unless of course you are targeting an alien carrying Blaster Bombs. Once MC chance is 18% or higher, MC is better, since the ratio becomes 3 panics to 1 MC. Anything in between is probably the commander's preference.

For an in-depth exploration of the psionic equations, including minimally and maximally effective soldier psi values versus the various aliens in the game, see Psionic Equations.