01
Shrink the kit to a few cues
Choose The tick. Every actor carries the same narrow receptors and can act on everything they deliver. One species, one world, and most of the environment simply missing from it.
communicoupling
The tick's world holds
three things.
A tick waits on a branch for the smell of butyric acid, drops, feels for warmth, then burrows where the hair thins out. Butyric acid, warmth, hairlessness. The mammal's colour, its heartbeat, the forest standing around it — none of that is dim or distant for the tick. It is absent.
Jakob von Uexküll called that world an Umwelt: everything an organism's receptors can register and its effectors can reach, and nothing else. Perception and action close a circle. What an actor can do settles what is worth registering, and what it registers settles what it can do.
sensory bandwidthfeature channels an actor's receptors register
action repertoirechannels its effectors can grip
kit diversityhow far actors' kits differ from one another
mean world
—
share of the environment an actor registers
shared world
—
objects standing in every actor's world at once
mutually invisible
—
actor pairs whose worlds hold nothing in common
One environment, as many worlds as there are kits
gold: everything an actor registers · green: the part it can also act on · violet: the floor every world contains
Set the conditions
what to try
Change the kit, change the world.
02
Give every actor a different kit
Choose Same street, four cities. World sizes fan out, the shared floor drops to the axis, and some pairs of actors register no object in common.
03
Widen one actor's receptors
Choose The trained eye. Bandwidth spreads across the population and the widest kit approaches the whole environment. Expertise shows up here as world size.
the mechanism
A world is an environment met by a kit.
The environment is a field of objects, each bearing one or a few feature channels. Every actor carries a receptor mask (the channels it registers) and an effector set (the channels it can grip). Both are picked by blending a salience ordering shared across the population against idiosyncratic weighting; kit diversity sets that blend and also spreads bandwidth across actors. An object enters an actor's world when it bears any channel that actor registers, and becomes usable when it bears a channel the actor both registers and grips.
Three quantities follow. Mean world reports how much of the environment an average kit reaches. The shared world is the intersection of every actor's world, and the narrowest kit present caps it. Mutual invisibility counts pairs with no object between them. Widening the action repertoire lifts the usable share without moving world size at all, which is the model's way of saying that grip cannot deliver what the receptors omit.
The circle runs one way here: effectors are drawn toward channels the actor already registers, while receptors ignore the repertoire. Von Uexküll's functional circle runs both ways, and a fuller model would let a new capacity recruit new receptors.
the social payoff
One corridor, several buildings.
A hospital corridor is a single structure and many worlds. The patient registers the distance to a door and the tone of a passing voice. The nurse registers a drip rate, a chart, a colleague's hurried step. The auditor registers a hygiene dispenser and an unlabelled trolley. Each acts on whatever shows up, so each leaves the corridor having been somewhere different.
Coordination therefore starts before disagreement does. Two parties registering different features are talking about different objects, and the repair is a change of kit: a shared instrument, a rehearsal, a vocabulary that makes a feature registrable. This is where umwelt meets affordances. An affordance needs an actor who can perceive it; an umwelt is the inventory of what that actor can perceive at all.
the mapping
Mechanism ↔ social life.
| In the model | In the world |
|---|---|
| feature channel | A property some receptor can pick up: a smell, a price, a legal category, a tell. |
| receptor mask | What an actor registers — trained senses, instruments, categories, habits of attention. |
| effector set | What an actor can act on — skills, tools, budget, authority, permissions. |
| world | Everything that shows up for that actor at all. |
| usable world | The part it can both register and grip; the functional circle closes here. |
| shared world | What every party registers, and the only ground a joint reference can stand on. |
| mutual invisibility | Parties whose worlds intersect nowhere; nothing they say finds a common referent. |
where it tears
Limits.
Pushed hard it becomes species solipsism.
If each kit seals its own world, communication across kits should be impossible, and it happens daily. A vet reconstructs what the dog registers. A translator carries a joke between languages. A blind reader and a sighted one argue about the same paragraph. Umwelten leak, and the traffic between them is the subject of this collection.
It cannot name what lies outside every umwelt.
Saying what the tick misses takes an observer with wider receptors, whose own umwelt then bounds the description. Von Uexküll left that regress open. Every claim about the environment as such is issued from inside some kit, this model included.
Worlds are expandable, and relativism forgets it.
"Everyone has their own world" flatters a stalemate. A microscope, a lab year, a case-law vocabulary, a second language — each grows the kit, and the model registers that growth as world size. Bandwidth is trainable, which makes the shared floor something a group can build.