Overview of the 2018 spoken CALL shared task

Research output: Chapter in Book/Report/Conference proceedingConference contribution


  • Claudia Baur
  • Andrew Caines
  • Cathy Chua
  • Johanna Gerlach
  • Manny Rayner
  • Helmer Strik

External organisations

  • University of Geneva
  • University of Cambridge
  • Radboud Univ Nijmegen


We present an overview of the second edition of the Spoken CALL Shared Task. Groups competed on a prompt-response task using English-language data collected, through an online CALL game, from Swiss German teens in their second and third years of learning English. Each item consists of a written German prompt and an audio file containing a spoken response. The task is to accept linguistically correct responses and reject linguistically incorrect ones, with “linguistically correct” defined by a gold standard derived from human annotations. Scoring was performed using a metric defined as the ratio of the relative rejection rates on incorrect and correct responses. The second edition received eighteen entries and showed very substantial improvement on the first edition; all entries were better than the best entry from the first edition and the best score was about four times higher. We present the task, the resources, the results, a discussion of the metrics used and an analysis of what makes items challenging. In particular, we present quantitative evidence suggesting that incorrect responses are much more difficult to process than correct responses and that the most significant factor in making a response challenging is its distance from the closest training example.


Original languageEnglish
Title of host publicationProceedings of Interspeech 2018
Publication statusPublished - 3 Sep 2018
EventInterspeech 2018 - Hyderabad International Convention Centre, Hyderabad , India
Duration: 2 Sep 20186 Sep 2018

Publication series

ISSN (Electronic)1990-9772


ConferenceInterspeech 2018


  • CALL, shared tasks, speech recognition, metrics