Why do characters with a high prime requisite gain bonus XP?

In earlier versions of Dungeons & Dragons, a character with a high ability score in their class' prime requisite receives a bonus to all experience he earns. For example, the 1983 Frank Mentzer edition included this chart:

Prime Requisite Score  Adjustment to Experience
3-5                     -20%
6-8                     -10%
13-15                    + 5%
16-18                    +10%


What is the reason for this rule? Did the game's designers ever explain it, either officially or anecdotally?

• Interestingly, prime requisite bonuses date all the way back to the original version of the game...the OD&D brown (and white) box rules. Page 11 of Volume One: Men & Magic lists "Bonuses and Penalties to Advancement due to Abilities". The adjustments appear to be very similar to those in the later 1983 Mentzer basic edition (the OD&D rules were first published in 1974). – Badmike May 13 '12 at 21:35
• If you want to know "what were they thinking" you'd need to ask Robert Kuntz as he seems to be the only one of the TSR originals still alive. Arneson, Kaye, and Gygax have all passed away. Tim Kask, Jim Ward, and Frank Mentzer may also have an insight due to how long they knew Gary G. – KorvinStarmast Sep 6 '15 at 15:44

When building characters, with "in order" statistic generation, or "assign existing roll" statistic generation, the XP bonus acts as an incentive to produce two outcomes. For "in order" character generation, it strongly suggests to players that they make their character "fit" their statistics, in particular by aligning their character selection with their highest statistic. No INT18 fighters please, we're Gygaxian. Correspondingly, with player assigned statistics (and points buy, obviously), it encourages characters whose statistics match their function in at least one statistic, their primary one. No STR18 WIS9 clerics please, we're Gygaxian.

Given that primary statistics also limit spells and levels; there is a strong rules based encouragement for character statistics to match assumed "rule ideal" types of characters.

Secondly, with statistic degrading poisons, traps, effects and magic; the loss of XP when your primary statistic is degraded below 9, is an encouragement for Fighters to regain their Strength, Clerics to regain their Wisdom, etc. Again, this encourages actual characters to match a rule ideal "type" of character at the level of statistics.

• Actually, the Stat minimum for spells was not in the Mentzer editions. So, having a spellcaster with a low Prime Requisite was no hindrance to their career apart from XP earned. – YogoZuno May 14 '12 at 8:14

This is just an opinion, but seeing the bonuses in original D&D (OD&D) since the beginning, they seem to be a way to subtly push the player towards a specific character class. Remember, in the early days, many systems (including OD&D) required you to roll three dice, in order, for your stats. So many players who wanted to work a fighter might end up with a 9 strength and a 17 wisdom, and they would just play the fighter despite having bonuses should they have played the cleric. It appears the prime requisite bonuses might be there to reward a player for "taking a chance" on a character class he might not normally choose. The 5-10 percent added to experience (in contrast to the 10-20 percent LOST if the prime requisite was 8 or under) would be a substantial bonus in early editions of the game where EXP were sometimes scarce and character longevity was not guaranteed.

EDIT: BTW, per a question by Yogo, here is the original Prime Requisite bonuses from the OD&D rules. It is interesting to note the changes from this to later editions:

In OD&D there are only three classes: Fighting Men, Magic Users, Clerics. All abilities are rolled by 3d6, in order.

STR is prime requisite for Fighting-Men. INT is prime requisite for Magic Users. WIS is the prime requisite for Clerics.

Bonuses and Penalties for Advancement Due to Abilities: Low score is under 8; Average is 9-12; High is over 13

Prime Requisite 15 or more: Add 10% to earned Experience Prime Requisite 13 or 14: Add 5% to earned Experience Prime Requisite 7 or 8: Minus 10% from earned Experience Prime Requisite 6 or less: Minus 20% from earned experience

There are ability bonuses given for high CON, DEX or CHR, but they are unrelated to Experience point awards. Interestingly, besides the Experience point bonuses there is little advantage to having a high STR, INT or WIS except for intangibles: A high STR is said to help in opening traps, A high INT will add languages and affect referees decisions about certain actions the player might make, A high WIS acts in the same way as a high INT (might affect decisions made per the referee's decision)

• 'despite having bonuses should they have played the cleric' - Sorry, but apart from bonus XP, the only benefit of a high Wis was a bonus on Saves, and that applied to all classes, not just Clerics. – YogoZuno May 14 '12 at 8:07
• See comment below...you really have to go back and find out why they are given in the Original (OD&D) rules before you extrapolate reasons for later editions, because in many cases those later editions are merely aping stuff that came before. – Badmike May 14 '12 at 16:39
• @Badmike Answers aren't necessarily displayed in a predictable order, so 'below' isn't necessarily a useful descriptor. Could you perhaps mention the name of the poster? – GMJoe May 16 '12 at 4:36

I'm only guessing here, but for the majority of classes under those systems, you were required to have a high value in your prime requisite, but there was virtually no system bonus for those high values. Sure, Str, Dex and Con gave all characters in-game bonuses, but high Int gave you nothing but languages. So, to me, the extra XP was a way of giving those high stats an in-game bonus.

• When you go back to Original D&D, ANY high ability in your prime requisite gave you a XP bump, while a low ability gave you a minus. This was a -20% to a +10% swing for some character that instead of playing a fighter with a 8 STR went with playing a cleric with a 15 WIS instead of vice-versa. Remember, most bonuses as we see them in the rules come from LATER editions, which piled up the benefits from high prime requisites...but their origins are from the first white box rules. So really you have to go back to the beginning and ask yourself why these bonuses were given in the OD&D rules. – Badmike May 14 '12 at 16:38
• I can't go back further than what I have - earliest rulebook I have is the first Mentzer edition. Thanks for clarifying. So, were there any other stat bonuses? To hit and damage for Str? – YogoZuno May 14 '12 at 23:12
• Yogo let me see if I have time to put up the "original" prime requisite bonus chart....it is very interesting in what was kept for later editions and what was left off. – Badmike May 15 '12 at 17:54