A paper on the British Council's Teaching English site by applied linguists Jeannette Littlemore, Fiona MacArthur, Alan Cienki and Joseph Holloway.
"In recent years there has been a significant increase in the number of international students studying at British universities. This paper reports on a study of oral interactions between lecturers and international students studying at a British university and a Spanish one. Metaphors and gestures were identified as being used successfully and less successfully in different exchanges. The paper concludes with a number of recommendations for making the most of the potential metaphor has to offer in academic tutorials."
The paper includes video clips and close analysis of speech and gestures in interviews involving native-speaking UK lecturers and non-native international students. It shows how comprehension problems occur due to use of metaphorical languages, but does not suggest native-speakers avoid such language, but rather suggests "ways for lecturers to accommodate to L2 speakers’ difficulties in understanding metaphorical language uses in ways that do not involve complete avoidance of metaphor or result in impoverishment of the interaction."