Hearing only one side of normal and mobile phone conversations

Mobile (cell) phone conversations are commonly perceived as annoying when conducted in a public space. An experiment is described that demonstrates one factor contributing to this phenomenon: hearing only one side of a conversation makes it more noticeable and intrusive. Two actors repeatedly staged the same conversation under three conditions: cell phone; normal, co-present both audible, and co-present only one audible. After the staged conversation, which took place on a train, a third person obtained verbal ratings from members of the travelling public. As in a previous experiment published in this journal, the cell phone conversation was rated as more noticeable and intrusive than the normal co-present both audible conversation. Critically, a new experimental condition, co-present one-audible, in which both actors were present but only one side of the conversation was heard, produced ratings equivalent to the cell phone condition. This 'need-to-listen' effect is discussed with regard to implications for design and theories of language use.