  Learning idiomatic expressions is seen as one of the most challenging stages
in second language learning because of their unpredictable meaning. A similar
situation holds for their identification within natural language processing
applications such as machine translation and parsing. The lack of high-quality
usage samples exacerbates this challenge not only for humans but also for
artificial intelligence systems. This article introduces a gamified
crowdsourcing approach for collecting language learning materials for idiomatic
expressions; a messaging bot is designed as an asynchronous multiplayer game
for native speakers who compete with each other while providing idiomatic and
nonidiomatic usage examples and rating other players' entries. As opposed to
classical crowdprocessing annotation efforts in the field, for the first time
in the literature, a crowdcreating & crowdrating approach is implemented and
tested for idiom corpora construction. The approach is language independent and
evaluated on two languages in comparison to traditional data preparation
techniques in the field. The reaction of the crowd is monitored under different
motivational means (namely, gamification affordances and monetary rewards). The
results reveal that the proposed approach is powerful in collecting the
targeted materials, and although being an explicit crowdsourcing approach, it
is found entertaining and useful by the crowd. The approach has been shown to
have the potential to speed up the construction of idiom corpora for different
natural languages to be used as second language learning material, training
data for supervised idiom identification systems, or samples for lexicographic
studies.
