institution/Wiki/gangs/Joining.md

Joining a gang

How Gangs decides who runs with a crew — and why a well-run colony keeps almost everyone out.

Membership is not random, and it is not a mood event. A pawn joins a gang only when their disposition and their circumstances line up at once — the same Nature × Nurture engine that drives every other behaviour in the Institution suite. This page covers the exact test, why the bar is set where it is, and how you keep pawns on the right side of it.

The rule

WouldJoin(pawn) == Propensity.Nature(pawn) * Propensity.Nurture(pawn) >= JoinThreshold
JoinThreshold = 0.9

Two gates before the maths even runs:

Guard	Effect
pawn == null	never joins
not RaceProps.Humanlike	never joins — animals and mechs are out

Then it is one line: multiply the pawn's Nature by their Nurture and compare to 0.9. There is no dice roll here. WouldJoin is a deterministic threshold on the two propensity scores, so the same pawn in the same situation always gives the same answer — join, or don't. (This is different from Core's Propensity.Would(...), which is a seeded random roll used for one-off acts like a piss spree. Gang membership is a standing condition, so it uses the raw product.)

The two halves

Both terms come from Institution: Core — see Core's own documentation for the full tables — but you need the shape of them to understand the bar:

• Nature (0..1) is who the pawn is: a base of 0.05, plus trait weights, clamped to [0, 1]. Psychopath +0.45, Bloodlust +0.35, Kleptomaniac +0.40, Greedy +0.25, Abrasive +0.15; and it goes down for Kind −0.30 or Ascetic −0.15. This is fixed at pawn creation and barely moves.
• Nurture (a multiplier, ~≥ 0.4, base 1.0) is the situation you put them in: a floored mood multiplies it up hard (roughly ×2.5 under 0.20 mood, ×1.6 under 0.35), being held while miserable adds more (×1.4), a hardened record (negative reform) raises it, and — critically — deterrence pulls it down (×Lerp(1.3, 0.7, deterrence), neutral 1.0 at baseline order, so a high-deterrence colony scales nurture toward 0.7). This is the half you control.

Why the bar is high

0.9 is a deliberately steep threshold. From the source, in its own words:

A high bar, on purpose: gangs are a symptom of a badly-run colony, not furniture. A healthy Rimworld — content pawns, an orderly colony — grows few gangs, if any.

Because the two terms are multiplied, both have to be substantial for the product to clear 0.9. A nasty pawn in a happy, policed colony has a low nurture and stays out. A saintly pawn in a hellhole has a near-zero nature and stays out. You only get a gang when a genuinely disposed pawn is also neglected or unpoliced — foul streak and bad situation, together.

That is the design speaking through the arithmetic: a gang is never bad luck. It is feedback.

Worked examples

All numbers below use Core's documented factors; the intermediate nurture figures are rounded to show the shape of the decision.

Pawn	Nature	Situation → Nurture	Product	Joins?
Kind colonist, ordinary life	0.05 − 0.30 → 0.00 (clamped)	content, ≈ 1.0	0.00	No — nature floors it
Greedy prisoner, content, policed	0.30	fed & high deterrence, ≈ 0.7	≈ 0.21	No
Greedy prisoner, starved & neglected	0.30	mood floored + held, ≈ 3.5	≈ 1.05	Yes
...same pawn, but you raise deterrence	0.30	× ≈ 0.7 → ≈ 2.45	≈ 0.74	No — deterrence tipped them out
Psychopath + Bloodlust, mood floored	≈ 0.85	mood floored + held, ≈ 3.5	≈ 2.9	Yes — nothing short of reform pulls this back

The middle rows are the whole game of it. The same greedy prisoner joins or abstains purely on how you run the wing. The Kind colonist and the near-maxed psychopath are the fixed poles: one essentially cannot join, the other essentially always will if you neglect them. Everyone in between is a policy choice.

The mod's own integration test asserts exactly these poles: a psychopath-plus-bloodlust pawn with a floored mood returns WouldJoin == true, and a Kind colonist in ordinary circumstance returns WouldJoin == false.

It works for every pawn, everywhere

There is no "prisoners only" special case. The comment is explicit:

Any pawn — colonist, prisoner, slave — can, wherever they are.

WouldJoin reads nothing about a pawn's secured status. A disposed free colonist can run with a crew on the outside; a prisoner can run with theirs on the inside; a slave likewise. This is what lets a gang span the wall — an outside member and an inside member of the same crew (see Networks and Smuggling). Being held raises nurture (misery), but it is not a requirement.

The cadence: the 5000-tick check

Membership is re-evaluated on a fixed interval by the gang map component:

CheckInterval = 5000 ticks
MapComponentTick: run only when TicksGame % 5000 == 0

5000 ticks is about 2 in-game hours (a RimWorld day is 60,000 ticks), or roughly 80 seconds of real time at normal (1×) speed. On each fire, the component:

1. Gathers crew — every spawned humanlike on the map for whom WouldJoin is currently true.
2. Pairs up unaffiliated members of crew who share a room and a bond into gangs (see Affiliations and Segregation).
3. Runs one round of network resupply inside each gang (see Networks and Smuggling).

Because the check re-reads WouldJoin every time, membership is live: a pawn whose situation improves past the point where the product drops back under 0.9 simply stops being eligible to form new bonds. The bar is not a one-time gate at recruitment — it is a standing condition the colony is continuously graded against.

How to keep pawns out

You do not fight the gang system. You lower nurture, which lowers the product, which drops pawns below 0.9:

• Feed them and give them recreation. Mood is the biggest nurture multiplier by far. A wing above 0.35 mood loses the ×2.5/×1.6 spikes entirely.
• Keep deterrence high (Institution: Justice). Deterrence scales nurture down toward 0.7; a well-policed colony is arithmetically less gang-prone. This is the row in the table above where the same greedy prisoner flips from joins to abstains.
• Reform, don't just punish. A hardened record (negative reform) raises nurture; discipline that actually reforms (positive reform) lowers it. Harsh punishment that prisonizes a pawn makes the gang problem worse, not better.
• Accept the two poles. A near-maxed psychopath will run with someone the moment you slip; a Kind pawn essentially never will. Spend your attention on the middle.

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Part of the Institution suite — Core · Contraband · Justice · Gangs (this). Each mod stands alone; together they are one system. AI disclosure: developed with substantial assistance from Claude (Anthropic).