1. Grounding in Communication Herbert H. Clark and Susan E. Brennan

2. 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]

3. 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

4. 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.

5. 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

6. 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

7. 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

8. Positive feedback continuers: *yeah*, mmhm, etc. relevant next turns: i.e., something that makes sense in context and continues the conversation Miss 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?

9. But... Why don't people just say 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, uh B: Tent worms. A: Yeah. B: Yeah. –But why? Time pressure Errors Ignorance

10. 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

11. 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." –Installments 123…45…6789 –Spelling Feinman, that's F-e-i-n-m-a-n

12. 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

13. Clark's features of communication Copresence Visibility Audibility Cotemporality Simultaneity Sequentiality Reviewability Revisability

14. 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

15. 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

16. 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

17. 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

18. 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 it TA: Did you include stdio dot h? [looks at student] Student: include what? TA: stdio.h. If you use printf or anything you need to include Student: um, [fidgets] TA: no, I don't see it there. You'll need to write Student: yeah [nods, moves to keyboard] TA: pound. err. sharp - shift-three - include angle bracket stdio.h angle bracket Student: ok [starts typing]

19. Now, in a chat room instead Student: I'm having trouble with my code. TA: Let me see…paste it in here Student: ok [pastes the code] TA: what's the problem? [copies and compiles the code] Student: it won't compile TA: looks like you need to include stdio.h TA: like this: #include Student: ok TA: because you're using printf TA: does that make sense? Student: yeah, I think so. We talked about that in class.

20. 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 …

21. Conclusions Grounding is essential to communication Communication is a collaborative activity Content affects grounding Medium affects grounding