Dungeons & Dragons makes ability checks a key part of play, but these checks took years to enter the game. How did ability checks advance from house rule, to optional rule, to a foundation of fifth-edition D&D?

Before D&D added ability checks, players found a style that mostly avoided a need for such rolls. See A Lack of Ability Checks Shaped How People Originally Played Dungeons & Dragons. Even so, characters tried things that the rules didn’t cover. For many of these actions, success or failure hinged on a character’s ability scores. Gary Gygax told dungeon masters to guess the odds of success and roll for it. But DMs and players wanted more consistency and less guessing.

In 1976, issue 1 of The Dragon printed “How to Use Non-Prime-Requisite Character Attributes” by Wesley D. Ives. The article proposes a sort of ability check before anyone coined a name for it.

This first ability check suffers from a mechanic so baroque that it reads like a gag.

To determine an action’s success, perform these actions:

1. Roll d100, add the ability score, and then use this result to determine which die to roll in step 2. On a result of 1-20 roll a d4; on 21-40 roll d6; on 41-60 roll d8; 61-80: d10; 81-100: d12. To cope with results higher than 100, create a house rule for this house rule.
2. Roll the die determined in step 1 and multiply the number by the attribute. This result becomes the chance of success.
3. Roll a d100. If the result is less than or equal to the probability from step 2, you succeed!

The method requires three rolls, multiplication of double-digit numbers, and a table. But if that seems too simple, the article offers optional rules accounting for character level and class. All this yields an outcome barely more realistic than a coin flip.

To settle on an ability-check mechanic that required so much fuss, the author must have seen checks as a rare undertaking.

Despite the tortured mechanic, the idea of ability check marks a major innovation. None of the few role-playing games available in 1976 featured anything like the concept. In a few years, every RPG would build on the idea.

In the Advanced Dungeons & Dragons Player’s Handbook (1978), Gary invented a playable ability check for the Dig spell. “Any creature at the edge (1’) of such a pit uses its dexterity score as a saving throw to avoid falling into the hole, with a score equal to or less than the dexterity meaning that a fall was avoided.”

By the late 70s, the method found in the Dig spell turned into common house rule: To make an ability check, players tried to roll under an attribute on a d20.

The 1980 D&D basic rules by Tom Moldvay made this house rule official. “The DM may want to base a character’s chance of doing something on his or her ability scores (Strength, Dexterity, and so forth). To perform a difficult task (such as climbing a rope or thinking of a forgotten clue), the player should roll the ability score or less on 1d20. The DM may give a bonus or penalty to the roll depending on the difficulty of the action.”

Meanwhile, other role playing games advanced the state of the art. Traveller (1977) introduced skills and a single mechanic for skill checks. Runequest (1978) boasted skills and “attribute rolls” that multiplied an ability by 5 to set a percentage chance of success.

In games with skills, the skills cover most tasks a player might attempt, so ability checks blur into skill checks. Fifth edition intentionally makes skills an addition to ability checks.

For AD&D, Gygax showed little interest in ability checks. Improvised rulings worked fine for him. (When the DM is E. Gary Gygax, no player quibbles with a ruling.)

As for skills, Gygax preferred to keep D&D’s class archetypes pure. His Unearthed Arcana (1985) added weapon proficiencies as a sort of weapon skill, but the narrow scope kept the sharp lines between classes. Oriental Adventures (1985) extended the concept to create non-weapon proficiencies—skills without the name. These new proficiencies never overlapped with class abilities.

After Gary left TSR in 1985, his successors on the AD&D team lacked the clout to make sweeping changes to the company’s flagship game. Nonetheless, their additions inched AD&D closer to matching the ability checks and skills in other role-playing games.

Ability checks finally reached AD&D in the Dungeoneer’s Survival Guide (1986). Although this book’s title suggests a focus on player strategy, this guide brought key rules innovations to AD&D. Here, the non-weapon proficiencies from Oriental Adventures became options in the primary game. When players used non-weapon proficiencies, they made proficiency checks to determine the outcome. These checks operated like ability checks, but proficiency improved the chance of success.

The new system of featured all the ingredients of a modern skill system, but suffered a few drawbacks:

• Class abilities already covered most of a character’s actions, so non-weapon proficiencies rarely came up in play.
• The phrase “non-weapon proficiency” proved unwieldy. The term evolved from Gary’s own work on D&D, but it forced a lot of extra syllables on players just to avoid contaminating D&D with anything called skills.
• Roll-under ability checks confused players and designers.

For D&D’s other d20 rolls, players aimed high, but for ability checks they aimed low. This simple difference fostered confusion. The original ability-check rule said, “The DM may give a bonus or penalty to the roll depending on the difficulty of the action.” That meant a bonus subtracted from the roll—an ugly break from intuition.

A cleaner method adds the bonus to the attribute, so players roll under a higher number.

By now, some Internet critics might scoff at my notion that adding roll-under checks to D&D confused people. I imagine an argument heaping contempt on idiots who clearly lack the intellectual capacity for RPGs. Go back to Candyland. Who would let roll-under checks trip them up?

The D&D team at TSR.

Sometime during playtesting, the Dungeoneer’s Survival Guide apparently switched its method of applying modifiers, but the book reached print with an incomplete change. The “Sage Advice” column in Dragon issue 118 tried to sort out the mess. “OK, OK, OK, already! You’re right—there is something wrong with the DSG non-weapon proficiency system.

“We went through the manuscript and thought we had caught all the places where the text needed to be changed. We missed a couple of simple ones, and this caused a tremendous problem in the system.”

TSR management insisted that second edition AD&D remain broadly compatible with the original. The Player’s Handbook (1989) included a corrected version of non-weapon proficiencies as an optional rule. Ability checks entered the core game, but languished in the glossary.

For D&D’s third edition in 2000, the designers finally gained leeway to correct old drawbacks. Ability checks flipped so players aimed for high rolls. Skills embraced the actions characters actually did in the game. And no one had to say or type “non-weapon proficiency” ever again (unless they tell this story).