I am puzzled by the definition of "cue" as opposed to "cause". I am reviewing the literature about self-generated action (Passingham et al 2010; Nachev 2010; Shuur & Haggard 2011). The authors talk about cues extensively, as conditions that prompt an action. My question is, in what way does a "cue" differ from a "cause"? I keep missing a deep grasp on this.