Common Ground Breakdown

Fluent communications among humans comes with a paradox. On the constructive side, we continually repair common ground without even noticing we're doing it. On the confusing side, we can completely fail to notice when common ground has broken down.

On our turn to speak, we watch the listener closely and adjust our pace or level of detail according to what we think the other person understands. We may notice a wrinkled brow and backtrack to fill in some detail. The speaker and listener may not even notice the backtrack. This is an example of continually repairing common ground, and an example of expertise and fluency. We do this without even noticing.

When listening we may avoid interruptions to allow the speaker to complete their thoughts fully. Listening includes holding onto moments of ambiguity awaiting further explanation to bring clarity. We don't even notice when the ambiguity gets so big that our brow wrinkles.

Fundamental common ground breakdown happens often.

Alice and Bob are experts in different parts of the system and diagnosing some symptoms together. Alice assumes Bob knows about XYZ. Bob knows nothing about it—doesn't even know to ask questions about it. As Bob does not wrinkle his brow nor ask questions, Alice fluently continues without sharing details about XYZ. Both Alice and Bob feel like they are communicating with common ground and the critical gap in understanding about XYZ goes unnoticed.

In hindsight, we might say Alice should not have assumed Bob knew. Or we might say Bob should have known. Either of those claims only work in hindsight.

When Alice is communicating with Cindy, who does also know about XYZ, the communications are more effective by skipping over details about XYZ to focus attention on other areas of confusion. For Alice, the absence of wrinkled brow in Cindy is indistinguishable from the absence of wrinkled brow in Bob.

John Allspaw shared a paper he loves: Common Ground and Coordination in Joint Activity: pdf . Capturing notes here especially for the notion of constant repair of common ground and the fundamental breakdown of common ground. youtube

Challenge: resist the temptation to read into this paper the things you already know: distributed systems consensus concepts, Conway's Law, CAP Theorem, microservice/monolith justification, Dunbar's Number. Ask yourself "how is this different from Conway's Law?" or similar.

Intention and Interdependence.

Bob and Alice are at a party. Bob is unsure exactly how to get home, but he lives near Alice, who does know her way. He could just follow Alice until he recognizes a familiar neighborhood. But Alice might drive too fast, race through a yellow light or similar. It is best if Alice knows Bob intends to follow her. If they use an intermediary, Carl, to arrange the convoy there are many ways the compact can be broken. Best if they communicate directly to setup the convoy. Bob and Alice may fail to agree. If Bob sees Alice turning down many side streets he may assume she doesn't know her way and abandon the convoy leaving Alice to worry where she lost Bob and circling back to try to find him. If Bob makes a momentary wrong turn, Alice might conclude that Bob has found his way so she can safely abandon the convoy.

While she is leading the convoy, Alice has to adapt her own goals. Drive more slowly than usual. Prefer major streets to more obscure shortcuts. Stop at lights she might have raced through. Agreeing to the compact of riding in a convoy, she adapts her own goals to include Bob's goals of finding a way to familiar roads. They must agree to signal to one another when they choose to abandon the convoy and go their own ways.

This is exploring one corner of Graceful Extensibility.

See also Law of Fluency.