011 min
The problem common ground solves
A speaker cannot say everything. Each sentence leaves out most of what the speaker knows, and the listener fills the gap from what both of them already share. If the listener lacks that knowledge, the message fails, and often neither person notices.
The usual failure in work settings looks like this. An engineer says, "Let's use the old flow for that." The engineer means the checkout flow from last year's redesign. A new product manager in the room has seen only the current flow and nods. Two people now believe they agree, and they do not. The sentence depended on common ground that only one of them had.
021 min
How common ground is built: grounding
Clark and Brennan studied how speakers close that gap. Herbert Clark and Susan Brennan put it this way in 1991: "All collective actions are built on common ground and its accumulation." Their example is two pianists who must play the same piece and keep the same tempo. Both tasks depend on shared knowledge. They name the process of updating it: "In communication, common ground cannot be properly updated without a process we shall call grounding."
Grounding has two phases. In the first, a speaker presents an utterance. In the second, the partner shows that they understood it. The contribution counts only when both phases are done. A nod, an answer that fits, or a repeat of the key words are all evidence of understanding. Silence is weak evidence, because it fits both understanding and missing the point.
People do not aim for perfect understanding, which would cost too much. Clark and Brennan call this the grounding criterion: "The contributor and his or her partners mutually believe that the partners have understood what the contributor meant to a criterion sufficient for current purposes." A casual remark needs little checking. A medication dose or a contract term needs a lot.
031 min
A real case: "Do you and your husband have a car?"
Clark and Brennan analyse a recorded conversation from the London-Lund corpus of spoken English. One speaker, Alan, asks the other, Barbara, a question. He breaks off in the middle of a word and starts again. Barbara interrupts with a repeat of the last words, as a request for clarification. Alan answers "Yeah." Only after that does Barbara answer the question itself.
The authors' reading is that Alan had spoken a question, but had not yet asked one. He had presented the words. The question became complete only when Barbara showed she understood it. This is the difference between uttering a sentence and doing what the sentence is meant to do.
041 min
How the medium changes grounding
Grounding costs effort, and the cost depends on the medium. Their rule is "By the principle of least collaborative effort, people should try to ground with as little combined effort as needed." What counts as effort changes from one medium to another.
The authors list eight constraints that a medium can impose. Clark and Brennan list eight constraints a medium may impose, and the first is copresence: "A and B share the same physical environment." In a meeting room people can point at the object under discussion. On a phone call they cannot, so they must describe it. Another constraint is reviewability: "B can review A's messages." In email the message stays and can be reread. In speech it fades.
The constraints give a practical rule. In a medium where the other person cannot see your face, you receive less evidence of understanding. You must ask for it, or supply the shared reference yourself.
051 min
How common ground shows up in product and engineering work
Written specifications are grounded poorly because the reader cannot interrupt. A designer handing over a file with no commentary relies on shared knowledge that the engineer may not have. The remedy is to state the assumption in the document, such as which state of the product the screen starts from.
New team members are a second place. A shared vocabulary is common ground built over months. A new person lacks it, and an experienced person cannot easily tell which of their words are specialised. The curse of knowledge describes this blind spot.
Remote work is a third place. A distributed team loses copresence and often visibility. Short check-backs, such as "Here is what I understood, is that right?", restore the evidence that a face-to-face conversation gives without effort. The cost of such checks is part of communication overhead, and it is usually smaller than the cost of acting on a misunderstanding.
061 min
Applying common ground
- Before a conversation, ask what the other person already knows about the topic. Do not use your own knowledge as the guess.
- Name a reference the first time you use it. Say which document, which version, which customer.
- Ask for a restatement when the decision is costly. "What will you do next?" is better than "Does that make sense?"
- Choose the medium for the stakes. A call or a meeting provides more evidence of understanding than a message.
- Write down what was agreed. This turns shared understanding into something both sides can review later.
071 min
When common ground fails
The risk is false common ground. Two people each believe that the other shares an assumption, and neither checks. The effect is hardest to catch when both are confident.
Two tells appear in practice. A decision that seems to have been made turns out to have been understood in two ways. A person is surprised that a term they thought was shared needs an explanation.
The opposite failure also exists. Checking understanding after every sentence slows work, and most small exchanges do not need it. The grounding criterion says the aim is understanding "sufficient for current purposes." The effort should rise with the cost of being wrong.
081 min
Common ground versus the cooperative principle
The nearest neighbour is the cooperative principle, the idea that speakers contribute what the conversation needs. It describes what a speaker should say. Common ground describes what the speaker can assume the listener already knows. The two work together. A speaker decides how much to say by judging what is already shared, and Clark and Brennan add that the two people must also confirm the result.
Common ground is also not the same as context. Context is everything around an utterance, including the setting and the time. Common ground is the part of it that both people know that the other knows.
091 min
Frequently asked questions
What is common ground in communication?
Common ground is the knowledge, beliefs and assumptions that two people share and know they share. Speakers use it to decide what to say and what to leave out.
What is grounding?
Grounding is the process of making sure a message was understood, so that it becomes part of common ground. It has a presentation phase and an acceptance phase.
Who developed the theory of common ground?
The psychologist Herbert H. Clark developed the theory with several co-authors. Clark and Susan Brennan described grounding in a 1991 chapter.
Why do misunderstandings happen if both people think they agree?
They can happen when each person assumes the other shares some knowledge. Neither checks, so the assumption is never tested.
How do you build common ground in a remote team?
Use short restatements, name references explicitly and write decisions down. These replace the evidence that a shared room gives automatically.
?3 questions
Questions people ask
What is common ground in communication?
What is grounding?
How do you build common ground in a remote team?
§1 source
Sources
Herbert H. Clark and Susan E. Brennan, "Grounding in communication", in L. B. Resnick, J. M. Levine and S. D. Teasley (eds.), Perspectives on Socially Shared Cognition, American Psychological Association, 1991, pp. 127-149. web.stanford.edu
