What variety of attention is automatically captured by peripheral cues?

Previous studies have shown that the voluntary allocation of attention to a location in space can influence accuracy in two ways. First, additional processing resources can be allocated to the attended location, leading to an improvement in perceptual quality for objects presented at that location. Second, decision processes can be restricted to information arising from the attended location, which improves accuracy without influencing the perceptual representation. The present study examined the operation of these two attentional mechanisms when nonpredictive peripheral cues were used to capture attention automatically. Experiment 1 showed that, like predictive cues, nonpredictive cues influence accuracy by summoning perceptual resources and also by influencing decision processes. However, both the cues and the targets in this experiment were defined by luminance increments, making it possible that the cuing effects were mediated by a task-controlled attentional set rather than being fully automatic. Experiments 2 and 3 examined this possibility by using luminance-defined cues and color-defined targets; evidence was again obtained for both perceptual-level and decision-level attention effects. The capture of attention by a nonpredictive peripheral cue thus appears to influence both perceptual resource allocation and postperceptual decision processes.