Linguistic Factors in Cockpit Communication Manfred Krifka Humboldt Universität, Berlin...

Linguistic Factorsin Cockpit Communication

Manfred KrifkaHumboldt Universität, Berlin

collaborating with:

Silka MartensFlorian SchwarzCarrie Clarady

Research on Cockpit Communication:Some Background

• Social dynamics of group interaction as an important factor in the origin of accidents and in the success of dealing with accident-prone situations (cf. Robert Helmreich, “Managing Human Error in Communication”, Scientific American 1997.)

• Crew Resource Management (CRM): Rating and improving of crew performance in aviation and other fields in which professional groups interact in situations with high task load.

• But over and above the general social dynamics of group interaction, there are specific problems relating to language and communication in such settings.

Cockpit Communication

Possible areas of research:

• Problems of language (e.g., the structure of human language, features of the technical language).

• Problems of communication (that is, problems of language use)

Cockpit Communication: Problems of Language

Cf. Stephen Cushing (1994), Communication Clashes and Aircraft Crashes.

• Misunderstanding of We are now at takeoff

implied in Tenerife accident in 1977

• Problems of sentence parsing:[back [on the power]][[back on] [the power]]

• Problems of phonological identification:climb to five zeroclimb two five zero

Cockpit Communication: Problems of Communication

• Mitigation of contributions especially by the lower-ranked pilot (First Officer or Engineer) for face-serving purposes.

Not very much more fuel.(Engineer to Captain five minutes before engine

stopped, United Airlines, Portland, 1978)

(cf. Charlotte Linde, “The quantitative study of communicative success: Politeness and accidents in aviation discourse”, Language in Society 17)

Cockpit Communication: Research Techniques

• Observation of real situations

• Transcripts of communication before and during accidents (recorded by Black Box and published by National Transportation Safety Board)

• Observation and ratings of communication of regular flights.

• Important data, but difficult to come up with generalization from particular cases.

• Observation of communication in flight simulators

• Experimental scenarios.

• Similar scenarios for different crews.

• Advanced simulator techniques guarantee closeness to reality.

• But: Simulator sessions extremely costly.

Group Interaction in High Risk Environments:

Linguistic Factors

GIHRE Subproject, sponsored by Gottlieb Daimler and Karl Benz Foundation.

First project phase at Department of Linguistics, University of Texas at Austin, with Carrie Clarady.

Linguistic Factors: First Project Phase

Basic Questions:

Correlation: Task Load Communicative BehaviorCorrelation: Crew Performance Communicative Behavior

Linguistic Factors: First Project Phase

Data:• Simulation flights on B727 with similar scenario, carried out by NASA, 1987• Transcribed by University of Texas Aerospace Crew Research Project(thanks to Bob Helmreich and Brian Sexton)• Every flight has 4 transcribed segments: A: climbout from SF, descent and landing into SAC: Medium task load. B: Descent, approach and landing at LAX, with runaway trim, jammed stabilizer, low oil pressure: High task load. C: Descent to SAC, missed approach: Medium task load. D: Diversion to SJC, with hydraulic malfunction, diversion to SFC, split flap malfunctio: High task load.• Performance of crews and crew members was rated• We investigated 5 (+ 1/2) flights (2 well-performing crews, 3 poorly performing crews) (alltogether 9 hours, 6900 thought units)

Communication Density:Thought Units per minute, Crew 4

0

5

10

15

20

25

30

35

40

45

Minutes

ATC Captain 1st Officer Engineer

Segment A Segment B Segment C Segment D

No difference in speech time well-performing / poorly performing crews

Factors

Presentation of Data:

Segments: A Medium (task load)BCD High (task load)

Crews: 3 Poor (crews)45813 Good (crews)

Data are given in proportion to “thought units”(chosen by transcribers)

Speaker and Addressee Roleper Thought Unit

Speaker Role per Thought Unit

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

Poor Good Medium High PoorM PoorH GoodM GoodH

Captain First Off Engineer ATC

• Captain assumes speaker role most often.

• Engineer assumes speaker role more often in high task-load segments.

Speaker and Addressee Roleper Thought Unit

Speaker Role per Thought Unit

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7



• Engineer is adressed more often in high task-load segments.

Addressee Role per Thought Unit

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45



Reference to Participants

Reference to Speaker, Addressee, Group per Th.Unit

00,050,10,150,20,25

Poor Good Medium High PoorM PoorH GoodM GoodHSpeakerAddresseeGroup• Slightly more reference to group in good crews, high task loadscf. Sexton, J.B. & Helmreich, R.L. (2000). Analyzing cockpit communication. The links between language, performance, error, and workload. Human Performance in Extreme Environments 5, 63-68.

Speech Act Classification

Question: Correlation Task Load / Group Performance <=> Speech Acts?

Classical Speech Act Classification: Austin, Searle.• Representatives

commit the speaker to truth of proposition, e.g. asserting, concluding; degree of commitment can vary, e.g. saying, hypothesizing; may relate to other parts of discourse, e.g. replying

• Directives speaker tries to get the addressee to do something, e.g. requesting, questioning; degrees can vary, e.g. suggesting, commanding

• Commissivescommit the speaker to an action, e.g. promising, threatening, offeringdegrees can vary, e.g. promising, guaranteeing

• Expressivesexpress a psychological state, e.g. thanking, apologizing, welcoming

• Declarationschanges the institutional state of affairs, e.g. baptizing, marrying, declare a person guilty

Problems of Speech Act Classification

• Existing classifications are difficult to apply• Difference between form and meaning

– Direct command: Close the door.(Command : Imperative)

– Indirect command: The door should be closed.(Command : Declarative)

– Indirect command: Why don’t you close the door? (Command : Question)

– Very indirect command: It’s cold in here. (not a command, but a statement (*please), but may have similar action implications as commands)

Problems of Speech Act Classification 2

• Individuating speech acts– ABC 801, that turn looks like it’s going to take you through,

so continue the right turn to 180.(Command, or Assertion + Command, or Attention-Call + Assertion + Command?)

– [8.1530] I’m on the air, so you get it.(Command, or Assertion + Command, or Motivated Command?)

• Neglect of communication-regulating acts– Call for attention, acknowledgements, repetitions etc.

do not figure prominently in speech act classifications– Some investigation of such features in Conversation

Analysis (Reference)

Problems of Speech Act Classification 3

• Multi-dimensional nature of speech acts– A question can be related to a statement,

a command, a prior statement, etc.:What’s the weather like in Sacramento?What should I do now?What did you say?

– A command can be related to an action, a statement, a question, a prior statement, etc.:Now you fly the airplane.Tell me what’s the weather like in Sacramento.Ask him what the weather is like in Sacramento.Tell me again, please.

Our Speech Act Classification

• A “pragmatic” approach: What is potentially predictive for crew performance?

• Does not follow formal, but functional criteria, if the intended function is clear.Why don’t we go to the book and see what you can do on it? is classified as a command, not a question.

• Classifies each previously identified thought unit as belonging to one speech act category.

Our Speech Act Classification (2)

• Combines speech act types (e.g., assertion of a proposition) with content features (e.g., report of action, report of previous report, prognosis, diagnosis)

• Factors out classification of question / answer:You got any problems classified as statement / questionYou want me to brief with you? as command / question

• Assumes a category of “regulatives” that are concerned with the proper flow of information

Speech Act Categories

Code Name Definition

staterep Status Report Reports current state (equipment, weather, etc.)

reprep Report of Report Rephrases information expressed before

actrep Reprot of Action Gives a report of an action by himself

prog Prognosis Predicts the likely course of future events

diag Diagnosis Explains past events

comm Command Requests an action by addressee

perm Permission Gives permission for action by addressee

repint Report of Intention Expresses an intention to act in a certain way

comply Comply Verbalizes an action that carries out a command

expr Expressive Verbalizes an emotion

ack Acknowledgem. Acknowledges that preceding act was understood

affirm Affirmation Acknowledges and affirms preceding act

rephrase Rephrase Acknowledges and rephrases preceding act

Searle’sClassificaiton

Represen-tatives

Directives

Commissives

Expressives

“Regulatives”

Examples of Speech Act Types

• Status Reports– [4.17] UH ROGER UH WE ARE OUT AT 1443 AND OFF AT 53 FROM SAN FRANCISCO– [4.62] UH, ABC 801, BE ADVICED THE METER LOCATOR OUTER MARKER IS UNRELIABLE,

I’LL CALL YOU AT METER– [8.28] WE HAVE AN UNDEREXCITED FAULT LIGHT ON, UH, NUMBER 3– [8.89] OKAY, WE’RE COMING TO 350 DESCENDING TO 5, ABC 801

• Reports of Action– [4.75] I KEEP LOOKING FOR THE ALTITUDE RIGHT HERE AND SEE 801– [4.111] I’LL PUT IT ON THE MISSED APPROACH ALTITUDE

• Reports of Report– [4.461] WELL, HE TOLD US BE READY FOR ILS 24 RIGHT– (Not used for reciting from manuals, or relaying information in general)

• Prognoses– [4.373] OKAY, SO I THINK IF WE DO THE TWO ENGINE, THE TWO GENERATOR

OPERATION THAT’LL BE UH, THE NEXT THING.

• Diagnoses– [8.111] I THINK WHAT THAT LIGHT WAS, WAS WHEN THAT FIELD, FILED RELAY TRIPPED.

Examples of Speech Act Types 2

• Commands– [8.94] HEY, WITH THIS FAULT LIGHT, WOULD YOU SWITCH ESSENTIAL POWER OFF OF

NUMBER 3, PLEASE FOR ME– [8.212] ABC 801, THAT TURN LOOKS LIKE IT’S GOING TO TAKE YOU THROUGH, SO

CONTINUE THE RIGHT TURN TO 180– [8.356] PRESS ON– [8.64] OKAY, NOW YOU FLY THE AIRPLANE– [8.224] WHY DON'T YOU MAKE IT 190.– [8.305] FINAL FLAPS SHOULD BE 30

• Permissions– [8.19] UNITED 801’S CLEARED FOR TRAFFIC. YOU CAN DESCENT AT PILOT’S DISCRETION.– [8.15] OH, WHATEVER YOU WANT TO DO HERE, BOB

• Complies– [8.414] [HOW ABOUT THAT BRAKE? NOW TRY IT.] NO.

• Report of Intention– [8.32] MEANWHILE I’LL TAKE CARE OF THE APPROACH/DESCENT HERE– [8.63] WE’LL…WE’LL TAKE CARE OF THAT

Examples of Speech Act Types 3

• Expressives– [4.185] UH, SHIT– [8.639] LITTLE DEVIL– [8.904] BOY THAT IS A LOT OF PRESSURE– [8.989] GREAT, EXCELLENT, NO, EXCELLENT– [8.1019] COME ON, BABY, COME AROUND HERE

• Acknowledgements– [4.13] [ABC 801, EXPECT ILS 16 APPROACH TO SACRAMENTO] OKAY.– [8.410] [I’L JUST CRANK IT AND YOU TELL ME WHEN TO STOP]. YEAH.

• Affirmations– [8.1075] [WELL WE GOT… WE’RE COMMITTED TO THE RIGHT] THAT’S RIGHT– [8.1120] [CANT’T DO IT] NO [AGREEMENT].– [8.1169] [SHOULDN’T BE THAT MUCH OF A PROBLEM]. NOPE, NO NO NO.

• Rephrases– [8.50] [ONE SIX RIGHT, APPROACH.] ONE SIX RIGHT, YEAH.– [8.1640] [GROUND SPOILERS, OUT SPOILERS] OUT SPOILERS.


Prognoses and Diagnoses per Thought Unit

0

0,01

0,02

0,03

0,04

0,05

0,06


Prognoses Diagnoses

More prognoses / diagnoses in well-performing crews.


More reports of intention in well-performing crews.

Reports of Intention per Thought Unit

00,010,020,030,040,050,060,070,080,09



• Slightly more questions in well-performing crews.

• More questions are answered in well-performing crews (0.54 in poorly performing crews, 0.77 in well performing crews)

Questions and Answers per Thought Unit

00,020,040,060,080,10,120,140,160,18

Poor Good Medium High PoorM PoorG GoodM GoodHQuestionsAnswers


• Fewer commands in well-performing crews.

• Fewer explicit complies in well-performing crews.

Commands and Complies per Thought Unit

00,050,10,150,20,25

Poor Good Medium High PoorM PoorH GoodM GoodHCommandsComplies


• Fewer expressives and emotional words in well-performing crews.

• Fewer expressives and emotinal words in situations of high task load for poorly performing crews.

Expressives and Emotion per Thought Unit

00,020,040,060,080,10,12

Poor Good Medium High PoorM PoorH GoodM GoodHExpressivesEmotion

Limitations of Study

Correlation Segements / Task Load only very coarse. Number of crews analyzed far too low for any significance measure. Quality of transcripts rather varied, e.g. no information about paralinguistic features. Information about flight scenario and precise timing of malfunctions was rather limited. Revisions of speech act categories necessary. No classification of higher-order features of communication.

Examples of features that were not encoded

Multiple rephrases (Crew 8)[8.146] E-C: CLIMB TO 500 FEET, PROCEED DIRECT SACRAMENTO VOR.

HOLD SOUTH 180 RADIAL, 5,000 FEET.C-E: 5,000?E-C: YEAH.C-E: AFTER 500, DIRECT TO VOR TO HOLD?E-C: RIGHT.C-E: OKAY, GOT IT

Invoking Crew Resources[8.1511] YOU CAN, YOU CAN LISTEN WITH ME, I MIGHT MISUNDERSTAND.[8.2167] WHAT ELSE? WHAT HAVE WE MISSED?

Prioritizing goals (Crew 8)[8.368] WE WON'T WORRY ABOUT ANY OF THAT STUFF.[8.2007] F-C: I'M WORRIED ABOUT THE GAS. WE'RE PISSIN' OUT 15,000

POUNDS AN HOUR.C-F: DON'T WORRY.C-F: DON'T WORRY.F-C: OK.C-F: I'LL TELL YA WHEN TO WORRY.

New Project Phase(June 2001 - )

Data:Flight simulator data, but with a much more constrained scenarioin which communication skills are crucial

Flight Simulator Scenario

Developed by Gerd Fahnenbruck, carried out by Lufthansa CityLine on Canadair Regional Jet

• Circling approach due to glide slope failure, runway has to be approached from unusual direction, a plane is blocking the runway, fly a go around

• Normal second approach, break down of glide slope requiring constant communication about altitude

• Take-off followed by double instrument failure requiring constant communication about conflicting values

Data, Transcripts, Analysis

• Video data (4 cameras) and audio data available

• 16 flights, average length 53 minutes

• Identification of three segments with different types of task load across crews.

• Careful transcriptions, including features of prosody, intonation, pauses

• Refined system of speech act classification, following “Qualitative Development Analysis” (T. Diegritz & C. Fürst, Empirische Sprechhandlungsforschung. Erlangen 1999):

Example: Steps of analysis (QVA)

Example: Steps of analysis (QVA)

so. wie weit sin mer? flaps ham wir twenty.So. How far are we? As for the flaps we have 20.

Example: Steps of analysis


• Description



• Description

After initiating the utterance with the particle soCaptain utters a question with rising intonation.

Directly after this, as the captain is looking at the instrument panel, he utters a statement with strongly rising intonation.



• Description

• Division in speech acts



• Description


There are three subsequent illocutionary acts:

• so

• wie weit sin mer

• flaps man wir twenty



• Description


• Context



• Description


• Context

Reading back:

Due to the instrument failure, first officer informs captain that he can only fly in stand-by mode.

Captain agrees that it would be best not to split up the tasksbut to let first officer fly alone in stand-by mode.

Captain remarks that he can still help a little bit.



• Description


• Context

• Explicit interpretative verbalization



• Description


• Context


We have made it clear how we will proceed.

Let us check the current state, to see how far we are in respect to the planned approachwith the instrument failure.

I will go ahead and check the flaps, which are 20.



• Description


• Context


• Perlocutionary effects



• Description


• Context



First officer reacts with a confirming ja.



• Description


• Context



• Aspects of development



• Description


• Context




• Thematic progression Captain marks a thematic break by ending the previous sequence of clarification and going on to deal with the problem himself.

• Relational development Captain integrates first officer actively and cooperatively in the problem solving process, by asking himself and the first officer and by answering his own question.



• Description


• Context




• Assigning speech act type



• Description


• Context





So. STRUCTURING SIGNALI indicate that I am about to start a speech act and that the previous discussion is over.



• Description


• Context





Wie weit sin mer? QUESTION(INFORMATION)I ask you and myself about the current state of

events.



• Description


• Context





Flaps ham wir twenty. ASSERT WITH EVIDENCE (“Feststellung”)

I state that the flaps are twenty (and I have direct evidence for it)

Features of our Speech Act SystemFeatures of our Speech Act System

Two further aspects of the speech act system we are developing:

- Speech Act Types

- Dialogue Structure

Dialogue Segment

(4) 906 Fio: ja (5) 906 Fio: dann warten wa bis auf n intercept(6) 907 Cap: weißte wir sollten alles raussetzen.

gear down und flaps thirty.(7) 907 Cap: dann ham wa das schon (8) 909 Cap: is keen problem für uns (9) 909 Cap: okay?(10) 911 Fio: .hh hmm (11) 913 Fio: ich bin mir nich sicher ehrlich gesacht. (12) 913 Fio: aber gut. versuchn wa s mal

SA# Line #

Examples: Speech Act TypesExamples: Speech Act Types

(4) Confirmation (BESTÄTIGUNG)

(5) Suggestion (VORSCHLAG)

(6) Suggestion (VORSCHLAG)

(7) Giving reasons (BEGRÜNDUNG)

(8) Statement (FESTSTELLUNG/BEHAUPTUNG)

(9) Request for reply/confirmation (HÖRERRÜCKMELD. FORDERUNG)

(10) Signal of doubt (ÜBERLEG/ ZWEIFEL ANZEIG)

(11) Objecting/Doubting (ANZWEIFELN/EINWENDEN)

(12) Conceding/Confirmation (ZUGESTEHEN/ BESTÄTIGUNG)

STACK

8 Classes of Speech Act Types:I. InformationII. Requests (direct/indirect)III. Agreement/NegotiationIV. DissentV. Question typesVI. ExpressivesVII. Interaction markersVIII. Others

I . INFORMATIONII . REQUESTS

(direct/ indirect)

I I I . AGREEMENT /

NEGOTIATIONIV. DISSENT V. QUESTION TYPES

HINWEIS OvRU! INI ANWEIS (FREUNDLICH, CPT)command

INI ZUSTIM Mpermission

REAABLEHN FRAG (INFORM ATION) INI

M ITTEILstatus report ?

INI ANW EIS (NEUTRAL, CPT )command

INI BEKRÄFTIG (FREM D)affirmation

REAVORSCHLAG ABLEHN REAFRAG (VERSTÄNDNIS Inhalt) INI

FESTSTELL (Ansage)status report

INI ANW EIS (NACHDRÜCKLICH,

CPT) = BEFEHL commandINI BEKRÄFTIG (SELBST)

affirmation

REAABSCHLAG FRAG (VERSTÄNDNIS akust.) INI

EXPLIZIER (Erläuter, Überleg

Laut) report of ANW EIS (FREUNDLICH, F/O )command

INI W IEDERHOL (FREM D)rephrase

REAEINW END (SELBST) FRAG (M EINUNG) INI

SPEZIFIZIER RIN ANW EIS (NEUTRAL, F/O )command

INI W IEDERHOL (SELBST)rephrase

REAEINW END (FREM D) FRAG (HANDLUNG) INI

BESCHREIB (nur Handlung!)report of action

INI QUASI-BEFEHL (F/O)command

INI BESTÄT (FRAGE)

"Antw ort"

REAKORRIGIER (SELBST) ANBIET INI

ANKÜND (einer Handlung)report of action

INI VORSCHLAG (F/O) INI BESTÄT (HANDLUNGsauff.)acknowledgm.,affirm

REAKORRIGER (FREM D) VERGEW ISS RIN

BEGRÜNDreport of intention

GEHORCH /ERFÜLL (CPT, F/O)

verbalisation of comply

REAVORSCHLAG ANNEHM REAW IDERSPRECHV I. EX PRESSIV ES

BEHAUPT

affirmation

INI ERLAUBnis geben s. D/Fpermission

REA ZURÜCKW EIS BESCHW ICHTIG

RECHTFERTIGreport of intention

REABITT (ASYM M ETRISCH) INI ZW EIFEL BEW ERT (NEG)

FOLGER RIN BITT (SYM M ETRISCH) INIVII. IN TERACTIO N M ARKERS V III. O TH ERS

BEW ERT (POS)

ZUSAM M ENFASSdiagnosis, rep of

RIN BEDANK REABEDINGUNG NENN ERSTAUN ÄUSSERexpressive ?

ERINNER RIN KENNTNIS=ACK "habe

verstanden" acknowledgment

REABEREIT (Bereitschaft

verbalisieren?)

INSISTIER

VERM UT (EINSCHÄTZ)prognosis ?

? HÖRERRÜCKM ELD (HRM , M R) RE ENTSCHEID LOBexpressive ?

PLAN HÖRERRÜCKMELD/ ANTW ORT

FORDER s. D/F

INI Gegenteil von LOB (nicht: TADEL)

PROGNOS GLIEDERUNG SIGNALISIER INI RAT (geben/holen?)

ÜBERLEG ANZEIG (v.a. nach

Frage) hesitation?

REA SICH ENTRÜSTexpressive ?

VERZÖGER=FÜLL (ALM , kein

SpA)

- ZUGESTEHpermission ?

W orksheet Speech Act Types (cf. Diegritz/Fürst)

assertinform

status report

present actionaction in future

report of action

give reasonsexplain

report of intention

conclude

summarize

remind

assume

I. INFORMATION

friendlyneutralemphatical

command Cpt

quasi-command F/O

comply

suggestion

II. REQUESTS(direct/indirect)

agree

selfother

affirmation

selfother

rephrase

actionquestion

acknowledge

accept suggestion

III.AGREEMENT/NEGOTIATION

selfothers

correct

selfothers

object

reject suggestion

IV.DISSENT

speech act remarks / short version / comments

distinction from simliar types

additional features / hints for analysis

SUGGESTION (F/O)

roughly the same as Linde’s "draft order"also: provoke order

Difference to DRAFT_ORDER: Intonation, much friendlier and more cautious;features: modal verbs, conjunctive, "I suggest..."

"we" is often used, but there are also cases like: "soll ich das jetzt so machen?" (should I do it this way?) [draft orders]

speech act precondition for performing this act

possible (typical) perlocutionary effects

Paraphrase

ACCEPT SUGGESTION

Adressee made a SUGGESTION

Adressee is happy that speaker accepts his/her suggestion

REJECT SUGGESTION

Adressee made a SUGGESTION

Adressee makes a (counter-) SUGGESTION of his own

speaker lets addressee know briefly that he/she does not accept the addressee's opinion or view; implicit forms (where the speaker signals his rejection through facial expressions and/or gestures) and explicit forms need to be distinguished.

Hierarchical Structure of Speech ActsHierarchical Structure of Speech Acts

Initial Reactive Reinitiative

Accepting Problematic Rejective

Statements Confirming Doubting Refuting Insisting

(also: Conceding Objecting

Prognosis

Report etc.)

Assertives

Structural Dialogue Analysis (Franke 1990)Structural Dialogue Analysis (Franke 1990)

• Analysis of sequential embedding in the communicative context

• Analysis of dialogue types (well defined sequences of speech acts)

• Basic unit: minimal dialogue


• With an initial speech act (ISA), speaker 1 states a communicative goal

• Speaker 2 can accept or reject this goal

• For different ISA‘s there are well-defined sets of possible answers


• Examples: Sp2

Sp1 answer 1 answer 2

• question answer refuse to answer

• assertion agree refute

• suggestion accept reject

• Further option: counter-initiative speech act

Options for speaker 1 in the 3rd move (in response to a rejecting or counter-initiative second move):

• Retractive SA (RETSA) give up original goal

• Revised SA (REVSA) modify original goal

• Re-initiative SA (REISA) repeat the same goal


Dialogue Structure in our Data SegmentDialogue Structure in our Data Segment

SA# structural type of SA

5 initial speech act (ISA)

6-9 counter-initiative speech act (GISA)

10-11 re-initiative speech act (REISA)

12 retractive speech act (RETSA)

Outlook on application of Dialogue StructuresOutlook on application of Dialogue Structures

• Assigning a structural type to speech acts enables us to represent a different dimension of dialogue

• The different ways that the crew‘s speech acts relate to each other is an indicator of their communicative behavior

• This type of extended speech act theory allows us to make a quantitative comparison of aspects of dialogue structure with crew performance ratings

Linguistic Factors in Cockpit Communication Manfred Krifka Humboldt Universität, Berlin...

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