Visual spatial attention span orientation can be either endogenous or exogenous (Chica,
Bartolomeo, & Lupiáñez, 2013). Endogenous orienting of attention is top-down, or voluntary
attention. Spatial attention is oriented endogenously when the observer chooses to orient his or
her attention to specific, relevant stimuli, usually by the interpretation of a cue that directs
attention to the target. In contrast, exogenous orienting of attention is bottom-up, or involuntary,
stimulus-driven attention. Exogenous stimuli comprise multimodal salient stimuli external to the
observer such as a moving or flashing target. Salient stimuli can exogenously capture the
observer’s attention even when he or she has not intended to direct attention to that target.