A Trialogue Based Spoken Dialogue System for Assessment of

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ing the feasibility of using dialogue systems for English language assessment and. presenting a three party trialogue based scenario in which conversational English. skills can be tested ,2 Related Work, Current assessments of spoken language proficiency both automated and human . scored are primarily based on the stimulus response model in which the test tak . er is first presented with stimulus material which could be an image a video a. reading passage a recorded conversation etc and is then prompted to provide a. spoken response crucially each prompt is not based on the preceding response. provided by the test taker and thus the assessment is not interactive Automated. systems for scoring these assessments have been shown to achieve promising per . formance levels both for tasks eliciting restricted speech such as reading a text. out loud 1 and those eliciting spontaneous speech such as summarizing a lec . ture 23 However none of these assessment systems have included interactive. tasks that are able to evaluate a language learner s conversational skills . Dialogue systems have shown great potential as an educational aid through the. use of interactive tutoring systems in content domains such as physics 5 7 alge . bra 10 and computer literacy 6 as well as for the purpose of developing litera . cy skills 16 In addition there have been several applications that have employed. spoken dialogue systems technology in the domain of foreign language learning to. develop interactive tasks for improving various aspects of a language learner s. proficiency For the most part however the linguistic skills evaluated through. these tasks have been limited to areas such as pronunciation e g 20 and vo . cabulary e g 4 and have not evaluated conversational skills that are necessary. for interactive communication although see 18 for an example of an interactive. language learning task involving role playing and problem solving with an auto . mated agent and 12 for a system that assesses cultural skills that are necessary. for successful second language communication The goal of this project is to. move beyond these relatively restricted types of tasks and design an interactive. system that can be used to assess a language learner s communicative competence. through their ability to participate successfully in an interactive conversation . 3 Trialogue Scenario Implementation, Interaction with the user in this system takes the form of a trialogue i e a conver . sation between the user and two virtual agents This form of interaction has been. demonstrated to facilitate feedback and scaffolding in tutoring systems since it. provides more opportunities for the user to assume different functional roles in the. interaction than in two party dialogues 8 13 The scenario is designed for chil . dren in elementary school grades 3 5 and thus takes place in settings which. should be familiar to young students such as classrooms and libraries and in . 195, Proceedings of 5th International Workshop on Spoken Dialog Systems. Napa January 17 20 2014, volves communication with other students and teachers The trialogue scenario. begins with a teacher giving information to the user and to a virtual student Lisa . The user must then relay the information to a second virtual student Ron who. was not present for the teacher s announcement As Ron asks questions to the us . er Lisa is available to provide scaffolding support to the user confirming correct. answers by the user and responding appropriately to incorrect or off topic re . sponses Figure 1 shows a potential sample interaction in the trialogue scenario. see 22 for further details about the trialogue materials used in this system . The teacher has explained that the students will be learning. about weather in different parts of the world Ron enters hav . ing missed the teacher s explanation , Ron What are we learning about today .
User WEATHER, Yes but it s not about any weather You need to tell Ron. Lisa , more , Ron What are we learning about today . User WEATHER AROUND THE WORLD, Yeah that s right We re learning about the weather around. Lisa , the world , Figure 1 A sample interaction in the trialogue scenario as implemented in the system. In order to implement this trialogue scenario in a spoken dialogue system sev . eral requirements had to be met two of which are discussed here The first major. requirement was the capability to support multiple visually and aurally distinct. agents within the system in order to represent the virtual agents in the scenarios . the teacher Lisa and Ron in this example The second major requirement was the. ability to preserve the dialogue history and to craft a custom dialogue manager us . ing this history to provide suitable feedback and scaffolding during the scenario . After exploring the available toolkits for dialogue systems we found that no sin . gle toolkit provided all of the needed functionality The Virtual Human Toolkit. VHTK 9 allows for quick creation of scenes with multiple computer animated. dialogue agents but the default dialogue manager the NPCEditor 14 is de . signed for building question answering characters 19 and is not easily customi . zable to handle other dialogue structures In particular NPCEditor does not pro . vide a straightforward way to find which parts of an expected response are. missing as in the trialogue illustrated in Figure 1 An alternative dialogue manag . er FLoReS 15 is due to be included in a future release of VHTK but was not. available at the time of this writing The Olympus framework 2 uses the more. flexible RavenClaw dialogue manager 3 which is capable of handling a wide. variety of dialogue structures but the Olympus framework was designed with te . lephony in mind and does not support visual representations of dialogue agents or. 196, Proceedings of 5th International Workshop on Spoken Dialog Systems.
Napa January 17 20 2014, multiple system voices by default So components from both toolkits were com . bined in order to utilize the benefits of each , Both toolkits consist of a collection of modules that communicate with each. other via messages sent to a centralized hub VHMessages in VHTK and Galaxy. messages in Olympus Thus by creating an intermediary module to connect the. two hubs we were able to combine the two toolkits into the single dialogue sys . tem which we present here This intermediary module was written in Java utiliz . ing the Java implementations of message handlers and senders for both message. protocols The next two sections present the components that were integrated from. each toolkit into the dialogue system Figure 2 shows the overall system architec . ture with the components from each toolkit In essence VHTK provides the front . end for the system delivering visuals and audio to the user and accepting user in . put while Olympus handles the back end natural language understanding dia . logue management and natural language generation , ASR NLU. PocketSphinx Phoenix, VHTK Olympus , DM, RavenClaw. Olympus , TTS NLG, TTS NVBG Rosetta, VHTK Olympus .
Figure 2 Dialogue system components,4 Virtual Human Toolkit. The Virtual Human Toolkit VHTK was developed at the USC Institute for Crea . tive Technologies Our system uses three modules from VHTK the virtual human. front end the automatic speech recognition module PocketSphinx 11 and the. text to speech module , The virtual human front end is built using Unity1 a multi platform game en . gine and IDE and consists of a number of virtual humans that can be placed into a. scene all of which are designed to respond to commands sent by VHTK Three of. these virtual humans were chosen one each for the teacher Lisa and Ron thus. 1 http www unity3d com, 197, Proceedings of 5th International Workshop on Spoken Dialog Systems. Napa January 17 20 2014, preventing the costly time sink of modeling our own agents for the system The. virtual human front end also integrates with the speech recognition module allow . ing users to indicate when they are speaking or to enter text and bypass the speech. recognition module if necessary The ASR output is sent to the Olympus compo . nents of the system and an utterance is returned to VHTK along with its speaker . VHTK then generates the spoken output either via TTS or via pre recorded audio. files For our system we use audio files which are pre generated from TTS in or . der to reduce response time VHTK also generates gestures and lip syncing for the. delivered utterances via its Non Verbal Behavior Generator Thus the combined. modules from VHTK allowed for rapid creation of high quality visuals with vastly. reduced effort compared to building a system from scratch . 5 Olympus, Olympus is a dialogue system framework created at Carnegie Mellon University .
The trialogue system uses three components from Olympus the Phoenix NLU. module 21 the RavenClaw dialogue manager 3 and the Rosetta NLG module. 17 The Phoenix NLU grammar consists of a set of slots which represent an . swers to questions from the characters in the trialogue with potential values for. each slot listed in the grammar The RavenClaw dialogue manager has a tree. structure with dialogue nodes executed in a depth first left to right order The. preconditions for entering and exiting each node determine the path through the. tree based on user responses i e the values of the slots from the Phoenix gram . mar Each node then specifies to the Rosetta module the type of natural language. output required optionally calling C procedures to perform more complicated. tasks as needed In Rosetta concrete realizations of each type of message are de . fined and for the trialogue system the speaker is prepended to the message so that. the generated voice and animations will be sent to the correct character in the. front end ,6 Discussion and Future Work, The approach to designing a spoken dialogue system for interactive language as . sessment described in this paper enables the use of multiple interactive agents with. distinct visual and aural characteristics combined with a robust custom dialogue. manager that enables scaffolding and feedback to the test taker throughout the. scenario The presented system was designed using components from two publi . cally available toolkits VHTK and Olympus along with a Java based intermedi . ary module to enable the communication hubs from the two systems to exchange. messages , Studies are currently being designed to evaluate the robustness of the presented. system in terms of ASR and NLU performance as well as its usability based on. user feedback After responses have been collected from participants they will be. 198, Proceedings of 5th International Workshop on Spoken Dialog Systems. Napa January 17 20 2014, provided with scores by expert human raters using scoring rubrics based on the. language learner s successful completion of the communicative tasks and respon . siveness to the feedback provided by the interactive agents Subsequently auto . mated scoring features will be extracted both from the dialogue flow for assessing. task completion and the spoken response for assessing second language speaking. proficiency and a system for the automated prediction of these scores will be de . signed , Acknowledgements, We would like to thank Youngsoon So and Diego Zapata for sharing the trialogue.
materials with us and Ben Leong for assistance using Olympus . References, 1 Bernstein J Van Moere A Cheng J 2010 Validating automated speaking tests Language. Testing 27 3 355 377 , 2 Bohus D Raux A Harris T Eskenazi M Rudnicky A 2007 Olympus An open source. framework for conversational spoken language interface research In Proceedings of Bridging. the Gap Academic and Industrial Research in Dialog Technology Workshop at NAACL HLT . 3 Bohus D Rudnicky A 2009 The RavenClaw Dialog Management Framework Architecture. and Systems Computer Speech and Language 23 3 332 361 . 4 Cai C Miller R Seneff S 2013 Enhancing speech recognition in fast paced educational. games using contextual cues In Proceedings of the 2013 Workshop on Speech and Language. Technology in Education , 5 Chi M VanLehn K and Litman D J 2010 Do micro level tutorial decisions matter apply . ing reinforcement learning to induce pedagogical tutorial tactics In Proceedings of the Interna . tional Conference on Intelligent Tutoring Systems Pittsburgh Pennsylvania 224 234 . 6 D Mello S K and Graesser A 2012 AutoTutor and affective autotutor Learning by talking. with cognitively and emotionally intelligent computers that talk back In ACM Transactions on. Interactive Intelligent Systems 2 4 , 7 Forbes Riley K and Litman D J 2012 Adapting to multiple affective states in spoken dia . logue In Proceedings of the 13th Annual Meeting of the Special Interest Group on on Discourse. and Dialogue SIGDIAL Seoul South Korea 217 226 , 8 Graesser A C Britt A Millis K Wallace P Halpern D Cai Z Kopp K Forsyth C .
2010 Critiquing media reports with flawed scientific findings Operation ARIES a game with. animated agents and natural language trialogues In J Aleven J Kay J Mostow Eds Lec . ture Notes in Computer Science 6095 327 329 London Springer . 9 Hartholt A Traum D Marsella S Shapiro A Stratou G Leuski A Morency L Gratch . provided by the test taker and thus the assessment is not interactive Automated systems for scoring these assessments have been shown to achieve promising per formance levels both for tasks eliciting restricted speech such as reading a text out loud 1 and those eliciting spontaneous speech such as summarizing a lec ture 23 However

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