Effects of varying target luminance and cue luminance on attentional effects of spatial cues

Landmark cueing and exogenous (onset) cueing: How are they related?

Attentional consequences of (i) mere onset of a peripheral visual cue, and (ii)encoding spatially predictive, landmark features of that cue were studied in two experiments. Target location was associated with landmark features of peripheral cues. Cue onset elicited both attention capture (Experiment Two) and inhibition of return (Experiment One) effects. In both experiments, attentional effects of landmark features of the cues were observed early in practice, and diminished with time on task. Contrary to hypotheses based on models that liken attention to a moving spotlight or zoom lens, in both experiments attentional effects of landmark features were confined to the location where the cue was presented. To explain this, we enlist the concept of attentional priority maps, and propose that visual encoding causes attentional priorities to be updated via alternative input routes and mechanisms. We suggest that onset cueing effects are associated with retinotectal 'spatial indexing', which registers the location, but not the attributes of new stimuli, while landmark cueing effects are associated with interaction between spatial indexing and dorsal stream visual processing of attentionally relevant landmark features.

Orienting of attention with and without cue awareness

Many cognitive processes operate without consciousness, and exogenous attentional capture seems to be one of them. While endogenously attending to the opposite location of a cue cannot occur without cue awareness, attending the cued location in an exogenous or stimulus driven form can occur even when participants are not aware of the presence of the cue (McCormick, 1997). Orienting attention to a specific location shortens reaction times to supra-threshold stimuli, and increases the likelihood of consciously perceiving near-threshold stimuli in that location. Effects of unconscious cues have mostly been demonstrated in reaction times to supra-threshold targets. In some studies, unconscious cues were perceptually less salient than conscious cues, which introduced a confound between cue awareness and cue saliency. In the present study, we used near-threshold cues and targets, which were titrated to be consciously perceived in ~50% of the trials, therefore eliminating the cue saliency confound. Moreover, we explored for the first time the effects of cue awareness on the conscious perception of subsequently presented near-threshold targets. Our results demonstrate that when cues and targets did not spatially overlap, conscious cues enhanced target localization when they appeared near the target location. In contrast, non-consciously perceived cues impaired target localization when they appeared near the target location, producing a cost in detecting subsequently presented near-threshold targets. This indicates that attentional orienting by unconscious cues cannot be accounted for by the idea that attention modulates perceptual representations, boosting them nearer to the conscious threshold. Rather, the effect of unconscious cues on target localization is qualitatively different to that elicited by conscious cues.