Grounding in Communication

Herbert H. Clark

and

Susan E. Brennan

Foreword:On analyzing conversation

• Real spoken conversation is very messy– incomplete sentences– overlapping turns– pauses– noisy voice data / unintelligible utterances

• Clark uses some standard notation for analyzing conversation– write out what was said, not good English– pauses in conversation: . , - [2 seconds]

Grounding in Conversation

• In order to have an effective conversation, the participants need to understand each other

• To do this they need to ground their communication– Listener has to notice that something was said– Listener has to hear what was said– Listener has to understand what was said– Listener has to understand what was meant

Grounding in Conversation

• So what is grounding?– Making sure that the listener understand what the

speaker said– Making sure the speaker knows the listener understood– Making sure the listener knows the speaker knows the

listener understood, etc.

So then what is common ground?

• Information that participants know that they all know:– Common cultural and social history– Public history of the interaction– Current public state of the interaction

• Common ground accumulates as the interaction continues

Evidence in Grounding

• Speakers attempt to make sure they were understood by listeners

• To do this, they look for evidence of understanding

• Speakers can look for both positive and negative evidence

Negative feedback

• Usually involves a new communicative action on the part of the listener– repetition

• "- have a car?"

– fill-in-the-blank• "have a what?"

– asking questions or for clarification– many other methods

Positive feedback

• continuers: *yeah*, mmhm, etc.

• relevant next turns: i.e., something that makes sense in context and continues the conversationMiss Dimple: "Where can I get a hold of you?"Chico: "I don't know lady. You see, I'm very ticklish."

• continued attention– Similar to continuants– But this can sometimes be hard to detect

• HELLO! ANYONE AWAKE OUT THERE?

But... Why don't people justsay what they mean?

• Principle of Least Collaborative Effort– Basically, people seem to minimize the amount

of effort they have to put out to achieve understanding

A: That tree has, uh, uhB: Tent worms.A: Yeah.B: Yeah.

– But why?• Time pressure

• Errors

• Ignorance

Grounding Changes With Purpose

• Participants alter their grounding methods according to situation and content– Alternative descriptions

• Adding more detail to ensure grounding

– Indicative gestures• Pointing, other gestures

– Referential installments• Breaking a description into understandable chunks

– Trial references• Speaker puts out a tentative reference; listener

ratifies or rejects it

Grounding verbatim content

• For complex content, participants have many strategies to ensure error-free communication– Verbatim displays

A: "Waltham, MA, 02454"B: "0-2-4-5-4"A: "That's right."

– Installments123…45…6789

– SpellingFeinman, that's F-e-i-n-m-a-n

Grounding in different media

• So how is this applicable to HCI?– Users of groupware systems will need to stay

grounded– Constructing systems to support this grounding

requires understanding how users operate– Different media that you provide will affect

how users stay grounded

• Clark identifies features of communication and relates how they affect grounding

Clark's features of communication

• Copresence

• Visibility

• Audibility

• Cotemporality

• Simultaneity

• Sequentiality

• Reviewability

• Revisability

Clark's features of communication

• Copresence– Users are near each other, and can point at

objects in common ground

• Visibility– Users can see each other; allows gestures, facial

expressions

• Audibility– Users can hear each other, and use natural

language

• Cotemporality– Users can expect to receive a timely reply;

interruptions or delays are significant

Clark's features of communication

• Simultaneity– Users can send and receive at the same time;

allows interruption, backchannel feedback

• Sequentiality– User contributions are strictly ordered, and

cannot get out of order

• Reviewability– Users can look at the past history of the

conversation

• Revisability– Users have the option of editing their

contributions before they commit to them

Some examples

• Face-to-face– Copresence, visibility, audibility, Cotemporality,

simultaneity, sequentiality

• Telephone / Voice over IP– Audibility, cotemporality, simultaneity, sequentiality

• Family radio / DirectConnect / walkie-talkies– Audibility, cotemporality, sequentiality

• Email/SMS/Text messaging– Reviewability, revisability

• Chat/IM/IRC/ICQ– Cotemporality, reviewability, revisability

Costs of Grounding• Different features affect cost for speaker and

listener to ground communication– Cost of formulation (deciding what to say)– Cost of production (saying it)– Cost of reception (hearing it)– Cost of understanding (understanding it)– Cost of start-up (starting a conversation)– Cost of delay (what impact a delay has)– Cost of asynchrony (what impact misordering has)– Cost of speaker change or multiple speakers– Cost of display / pointing / graphical input– Cost of errors (in production or in understanding)– Cost of repairs

A made up example: face-to-face

Student: I'm having trouble with my code.TA: Let me see… [looks at window full of code]Student: It doesn't compile, I think itTA: Did you include stdio dot h? [looks at student]Student: include what?TA: stdio.h . If you use printf or anything you need to

includeStudent: um, [fidgets]TA: no, I don't see it there. You'll need to writeStudent: yeah [nods, moves to keyboard]TA: pound . err . sharp - shift-three - include angle bracket

stdio.h angle bracketStudent: ok [starts typing]

Now, in a chat room instead

Student: I'm having trouble with my code.TA: Let me see…paste it in hereStudent: ok [pastes the code]TA: what's the problem? [copies and compiles the code]Student: it won't compileTA: looks like you need to include stdio.hTA: like this: #include <stdio.h>Student: okTA: because you're using printfTA: does that make sense?Student: yeah, I think so. We talked about that in class.

Comparison:face-to-face v. chat

• Easier to point• Easier to discuss• Easier to gauge

understanding• …

• Easier to produce complicated content

• Easier to review history of conversation

• …

Conclusions

• Grounding is essential to communication

• Communication is a collaborative activity

• Content affects grounding

• Medium affects grounding