Phasic Alertness is Unaffected by the Attentional Set for Orienting

Warning stimuli preceding target stimuli for behaviour improve behavioural performance, which is referred to as phasic alerting. Similar benefits occur due to preceding orienting cues that draw spatial attention to the targets. It has long been assumed that alerting and orienting effects arise from separate attention systems, but recent views call this into question. As it stands, it remains unclear if the two systems are interdependent, or if they function independently. Here, we investigated whether the current attentional set for orienting modulates the effectiveness of alerting. In three experiments, participants classified visual stimuli in a speeded fashion. These target stimuli were preceded by orienting cues that could predict the target's location, by alerting cues that were neutral regarding the target's location, or by no cues. Alerting cues and orienting cues consisted of the same visual stimuli, linking alerting cues with the attentional set for orienting. The attentional set for orienting was manipulated in blocks, in which orienting cues were either informative or uninformative about the target's location. Results showed that while alerting generally enhanced performance, alerting was unaffected by the informativeness of the orienting cues. These findings show that alerting does not depend on the attentional set that controls orienting based on the informational value of orienting cues. As such, the findings provide a simple dissociation of mechanisms underlying phasic alertness and spatial attentional orienting.