Musical improvisation is a complex cognitive process based on an auditory-motor learning that has to come into play to convey intentions and personal affects to others, as a story telling. While improvising, performers provide nonverbal cues as a driving force of the music that are called "backchannels", and that serve communicative aspects to regulate and monitor musician's playing, but also aesthetic aspects for which observers are sensitive. Therefore, to better communicate and understand each other's, musicians in interaction also shared different information as “common ground” such as mutual knowledge, beliefs and assumptions, as any form of social communication. Based on Moran and colleagues' study (2015) who showed no significant difference between standard jazz musicians, free improvising musicians, non-musicians and non-improvising musicians regarding the detection of backchannel cues of a musical improvisation duo in a freely jazz improvised condition, we tried to determine whether or not musical expertise, empathy and cue deprivation would influence observer's judgement of nonverbal feedback...