Sheremata, Summer

In everyday life, we come across visual distractors such as crossing the street or driving down the highway, but what properties of distractors determine whether they will affect cognitive processing? Relatively little is known about how the strength of a distractor or changing it over time affects the ability to deploy attention. Previous studies have shown that suprathreshold stimuli interfere more in the Simon Effect than near threshold stimuli. However, it is unknown whether this effect is due simply to motor inhibition or generalizes to tasks without a motor component. To test the generalizability of this effect, an attentional blink task was presented in which a coherent motion stimulus surrounded a rapid serial visual presentation stream. The study demonstrated that the highest coherence condition presented first had the greatest effect on performance accuracy. This is suggestive of a diffused attentional state.

Spatial-based attention is shown to vary in strength over short intervals of time. Whether object-based selection also has similar temporal variability is not known. Egly, Driver and Rafal (1994) demonstrated using 2-rectangle displays how both spatial and object-based selection engages in processing of a visual scene. In Experiment-1 using the 2-rectangle paradigm we measured temporal variability of target detection by presenting targets at a variable SOA. In Experiment-2, we used 4-squares to preclude any object-based selection and measured temporal variability in target detection at similar locations as in Experiment-1. We found target detection to be periodic in delta and theta hertz rhythm in both Experiment-1 and Experiment-2 upon comparing corresponding cue-valid and same-object locations. Similar spectral profiles across experiments indicate a split-spotlight of spatial attention that rhythmically monitors cue-valid and other invalid locations. Future experiments are needed to determine whether object-based selection is periodic in nature.