Instinct · Terrarium

When no language model is deciding for someone (in your browser, or without an API key), they act on instinct: fast, automatic responses that need no deliberation. Instinct is a baseline and a fallback. Deliberate choices, including whether to fight or keep the peace, belong to the model when there is one.

The instinct rules aren’t hand-picked thresholds. Each comes from a model in behavioural ecology or social psychology. Where a model gives the shape of a rule but not its numbers, the constant is listed as a calibration.

One currency: getting through the week

Every instinctive choice is weighed in a single currency: a person’s chance of getting through the next few days. Food gained, an injury risked and harm done to others then become comparable (McNamara & Houston 1986).

That chance rises with food and health and falls with hunger, and each extra day of reserves matters less the better off someone already is. Food matters far more to the hungry than to the fed, and most of what follows comes from that.

The rules

Behaviour	Rule	Based on
Sharing	Give what helps the other more than it costs you, weighted by how much you care about them: kin by relatedness, friends by liking, others by a baseline, plus the balance of past gifts	Hamilton’s rule (1964); welfare tradeoff ratios (Tooby et al. 2008); reciprocity among foragers (Gurven 2004)
Taking by force	Only from someone not expected to share anyway, and only when the gain beats the risk of being hit back, the harm done and being seen	Resource-holding potential (Parker 1974); tolerated theft (Blurton Jones 1984); harm aversion (Crockett et al. 2014); revenge as deterrence (McCullough et al. 2013)
Land	Intruders yield to a watching owner unless the patch is worth a fight; owners tolerate kin and friends	Hawk–dove and the bourgeois convention (Maynard Smith & Price 1973; Maynard Smith 1982); territory and property (DeScioli & Wilson 2011)
Foraging	Work a patch while it yields, then move to the best one in sight, then to remembered food	The marginal value theorem (Charnov 1976)
Families	Breed when in good condition and able to afford it, never with kin; keep close to a partner	Capital breeding (Jönsson 1997); the Westermarck effect (Lieberman et al. 2007); pair bonding (Fletcher et al. 2015)
Social life	Court the familiar and liked; warn friends about anyone who has done harm; teach kin	Propinquity (Festinger et al. 1950); prosocial gossip (Feinberg et al. 2012); teaching among kin (Kline 2015)

Agreeableness scales how much others’ welfare and social norms weigh, as it does in people’s handling of conflict (Jensen-Campbell & Graziano 2001).

What comes out of it

These outcomes aren’t written in as rules; they follow from the ones above.

Sharing pre-empts conflict. A surplus is worth little to its holder and a lot to someone hungry, so food flows to the hungry before force pays off.
Force appears under scarcity. Attacks and land disputes show up when food is short and trust is low, as cross-cultural data link unpredictable shortfalls and mistrust to violence (Ember & Ember 1992).
Kin are spared. Relatives are neither robbed nor driven off.

The full rules, the calibration constants and the references are in docs/INSTINCTS.md.