Hazard levels of warning signal words modulate the inhibition of return effect: evidence from the event-related potential P300.

Warning signal words are often used to convey valuable information about potential dangers in everyday life. In this study, we explored whether and how the hazard level of warning signal words modulated participants' attention to subsequent targets. Event-related potentials with high temporal resolution were employed in a cue-target paradigm. In this task, warning signal words with different hazard levels were used as cues. Participants were required to judge whether targets were presented on the screen horizontally or vertically. We found an inhibition of return (IOR) effect, i.e., participants had longer reaction times to validly cued targets than to invalidly cued targets. Accordingly, the IOR effect was reflected by a smaller P300 amplitude for invalidly cued targets compared to validly cued targets. Furthermore, the IOR effect was eliminated when the cues were high-hazard words. The dampening effect on the P300 was eliminated when the cues were high-hazard warning signal words. The lack of an IOR was attributed to participants' attentional bias to high-hazard stimuli, which are difficult for participants to disengage their attention from. The current study suggests that warning signal words are a particular type of stimulus that can override the IOR effect. Warning signal words with a high hazard level are more effective in successfully alerting people to risk in a hazardous environment.