10 KiB
Propensity — nature × nurture
Propensity is the suite's disposition engine. It answers one question and only one: "would this pawn do it?" — never "would a prisoner," never "would a colonist." Every behaviour in the suite that hinges on a pawn's character comes back to this, so crime, contraband brewing, escape arming, and gang recruitment all read the same answer instead of each guessing.
The model is deliberately old-fashioned: nature × nurture.
- Nature is a fixed property of the person — their traits. Almost nobody is strongly disposed, and this never changes over a pawn's life.
- Nurture is what the colony has done to them — mood, mistreatment, unmet needs, the shadow a sentence leaves. This is the half you control, and the half no other mod models.
Good conditions pull nurture down; neglect and cruelty push it up. A saint left to rot can cross the line; a monster kept content and deterred may never act. Both of those stories are possible by design.
Nature — who they are
Every pawn starts from a baseline of 0.05 — the floor of the human condition in this model: everyone is capable of something, most people barely. From there, each trait the pawn has adds or subtracts, and the total is held to the 0–1 range (never below 0, never above 1).
Trait weights
Traits are matched by name, so if a trait's mod isn't installed that entry is simply skipped. That's how Core uses Vanilla Traits Expanded's dark traits when VTE is present without requiring VTE to be installed.
| Trait | Weight | Source | Note |
|---|---|---|---|
| Psychopath | +0.45 | Vanilla | no empathy; the heaviest single input |
| Kleptomaniac | +0.40 | Vanilla Traits Expanded | counted if VTE is installed |
| Bloodlust | +0.35 | Vanilla | enjoys violence |
| Pyromaniac | +0.30 | Vanilla Traits Expanded | counted if VTE is installed |
| Greedy | +0.25 | Vanilla | wants more than their share |
| Abrasive | +0.15 | Vanilla | friction with everyone |
| Ascetic | −0.15 | Vanilla | wants little, takes little |
| Kind | −0.30 | Vanilla | the strongest pull down |
Core adds no traits of its own — it reads the ones the game and your other mods already provide. Vanilla's own dark traits count right alongside VTE's.
Worked Nature values
Because weights simply add and then clamp, Nature is easy to read by hand:
| Pawn | Arithmetic | Nature |
|---|---|---|
| Ordinary pawn (none of the above) | 0.05 | 0.05 |
| Kind pawn | 0.05 − 0.30 = −0.25 → clamp | 0.00 |
| A single Greedy trait | 0.05 + 0.25 | 0.30 |
| Psychopath | 0.05 + 0.45 | 0.50 |
| Psychopath and Kind | 0.05 + 0.45 − 0.30 | 0.20 |
| Greedy + Abrasive | 0.05 + 0.25 + 0.15 | 0.45 |
| Psychopath + Bloodlust + Kleptomaniac | 0.05 + 0.45 + 0.35 + 0.40 = 1.25 → clamp | 1.00 |
Two things fall out of this. First, the clamp isn't decorative: a Kind pawn floors at exactly 0
(nature can never make them disposed, only never disposed), and a stacked monster ceilings at 1.
Second, traits genuinely net against each other — a Kind Psychopath is a real, middling 0.20, not a
contradiction.
Most rolled pawns sit at or near the 0.05 floor. That's intended: a colony full of ordinary people
is supposed to be mostly safe on nature alone. What makes them dangerous is nurture.
Nurture — what you have done to them
Nurture is a multiplier. An ordinary pawn under ordinary conditions sits at 1.0. The number rises as things go wrong and falls as they go right. Each lever below stacks on top of the last.
The multiplier ladder
| Lever | Factor | Applies when | Stacks? |
|---|---|---|---|
| Despair | ×2.5 | mood below 20% | mutually exclusive with "badly kept" |
| Badly kept | ×1.6 | mood 20–35% | mutually exclusive with "despair" |
| Held & unhappy | ×1.4 | held and mood below 40% | on top of the mood lever |
| Prisonization | × (depends on reform, see below) | the pawn has a non-zero reform score | on top |
| Deterrence | × (the colony's climate of order) | always (neutral 1.0 with only Core) | on top |
The two mood levers are either/or: a pawn is either in despair or badly kept, never both. "Held &
unhappy" is separate and multiplies again — so a mistreated prisoner in despair compounds
2.5 × 1.4 = 3.5 before anything else. That is a badly run cell.
Prisonization — the reform lever
The reform lever is where a sentence leaves a permanent mark. A pawn's reform score runs from about −1 to +1 and turns into a multiplier:
| Reform score | Meaning | Factor |
|---|---|---|
| +1.0 | fully rehabilitated | 0.50 |
| +0.5 | improving | 0.75 |
| 0 | untouched (no effect) | 1.00 |
| −0.5 | hardening | 1.25 |
| −1.0 | prisonized | 1.50 |
| beyond +1.2 | (over-reformed) | floors at 0.40 |
| beyond −2.0 | (utterly broken) | ceilings at 2.00 |
Reform is nominally a 0-to-1 rehabilitation score, but harsh punishment can drive it negative — that's the "hardened, prisonized" end. Within the realistic −1…+1 range the factor spans 0.5…1.5; the 0.4 / 2.0 limits only bite at the extremes, catching a pawn who's been endlessly punished or endlessly rehabilitated.
Propensity only reads this score — nothing in Core moves it. The Justice layer's discipline and parole are what nudge it up or down, which is how institutionalization and recidivism enter the game without a separate mechanic. A pawn broken by a brutal prison stays broken (nurture ×1.5) after release; a pawn genuinely reformed stays calmer (×0.5) for good. The scar rides on one number.
Deterrence — the climate of order
The final lever multiplies by the colony's overall climate of order. With only Core installed it's neutral — a flat 1.0 — because Core by itself doesn't know what deterrence is. Install Institution: Justice and it fills this in: a well-policed colony pulls the factor below 1 and deters everyone a little; a lawless one pushes it above 1 and emboldens them. That's what makes catching and punishing one pawn matter to the disposition of the rest.
With only Core installed, this lever does nothing, and that is correct. The technical details of how a mod fills in deterrence are on the Modder API page.
Would — the full roll
Nature and Nurture are ingredients. The full roll is the meal: the actual yes/no for a specific behaviour at a specific base rate. For a given behaviour, the chance works out to:
chance = base rate × (0.1 + Nature × 2) × Nurture, capped at 85%.
Three things are happening there:
- Base rate is the behaviour's own dial — how likely an average pawn is to do this particular thing (a rare act uses a small number, a common one a larger). Core doesn't decide it; whichever system is asking does.
- (0.1 + Nature × 2) is the nature amplifier. It spans ×0.1 (a saint, Nature 0) to ×2.1
(Nature 1). At the common
0.05floor it's ×0.2 — so an ordinary pawn is one-fifth as likely as the base rate, while a maxed monster is over twice as likely — before nurture. - × Nurture applies circumstance on top, and the whole thing is capped at 85% by default. Nobody is ever a dead certainty; there's always slack. A behaviour that wants a harder or softer ceiling can set its own cap.
Worked example 1 — an ordinary colonist, content
Base rate 10%, an ordinary pawn (Nature 0.05), good mood so Nurture 1.0:
- nature term = 0.1 + 0.05 × 2 = 0.2
- chance = 0.10 × 0.2 × 1.0 = 0.02 → 2%
Two percent — and, critically, fixed. For this pawn and this question it's a settled 2% coin that either comes up or doesn't; it isn't re-flipped every moment.
Worked example 2 — a mistreated psychopath prisoner
A Psychopath + Bloodlust prisoner (Nature 0.85), mood 15% (despair ×2.5), held and unhappy (×1.4), reform −0.5 (hardening → ×1.25), Core-only so deterrence 1.0. Base rate 10%:
- nature term = 0.1 + 0.85 × 2 = 1.8
- nurture = 2.5 × 1.4 × 1.25 = 4.375
- chance = 0.10 × 1.8 × 4.375 = 0.7875 → ~79%
Same base rate as example 1, same engine — but nature and a badly-run cell have turned a 2% pawn into a near-certainty. The player did that, lever by lever.
Worked example 3 — hitting the cap
A fully stacked monster (Nature clamps to 1.0), in despair (×2.5) and held & unhappy (×1.4), in a lawless colony where Justice has set deterrence to 1.4. Base rate 10%:
- nature term = 0.1 + 1.0 × 2 = 2.1
- nurture = 2.5 × 1.4 × 1.4 = 4.9
- raw chance = 0.10 × 2.1 × 4.9 = 1.029
- capped at 85%
The raw product blew past 100%; the cap reins it to 85%. Even here, a 15% sliver of "not today" survives. That sliver is deliberate — it keeps the worst pawn a character with a bad day coming, not a scripted event.
The fixed roll — characters, not a dice cup
Each pawn's answer to "would they?" is fixed by two things: who the pawn is (their permanent identity) and which behaviour is being asked about. It is not re-rolled from scratch each time. This is the single most important design decision on this page, and it's worth being precise about why.
Save/reload stability. Because the answer is tied to the pawn's permanent identity and the specific question — not to the live random stream — asking "would they?" gives the same answer before and after a save/reload, as long as the inputs (traits, mood, reform) are the same. You can't scum a reload to re-roll a pawn into a different person. Who they are doesn't shift under them on a reload.
A character, not a moment-to-moment lottery. If the game flipped a fresh coin every tick, any pawn would eventually do anything if you waited long enough. Fixing the roll instead makes "would this pawn pocket a shiv?" a settled fact about that pawn under those conditions — what makes them a character, not a dice cup.
Live circumstance still bites. The roll freezes the identity, not the situation. Nurture is recomputed live, so as mood collapses or reform hardens, the same pawn's chance climbs and the same fixed coin can flip from "no" to "yes." The pawn who wouldn't have acted last month acts now — not because the dice changed, but because you let their world get worse.
Different questions, independent answers. Each behaviour is its own separate question, so the answers don't leak into each other: a pawn who would pocket a shiv is not therefore a pawn who would inform on a cellmate. One pawn can be reliably one kind of trouble and reliably not another, and that pattern is stable across the whole game.
Part of the Institution suite.