Influence of hand position on the near effect in 3-D attention.

Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations nearer the viewer once attention is deployed to a spatially cued object in depth. Previously, this effect (initially referred to as the near effect) was attributed to access of a 3-D viewer-centered spatial representation for guiding attention in 3-D space. The aim of this study was to investigate whether the near effect could have been associated with the position of the response hand, which was always near the viewer in previous studies that investigated endogenous attentional shifts in real depth. In Experiment 1, the response hand was placed at either the near or far target depth in a depth-cuing task. Placing the response hand at the far target depth abolished the near effect, but failed to bias spatial attention to the far location. Experiment 2 showed that the response hand effect was not modulated by the presence of an additional (passive) hand, whereas Experiment 3 confirmed that attentional prioritization of the passive hand was not masked by the influence of the responding hand on spatial attention in Experiment 2. The pattern of results is most consistent with the idea that response preparation can modulate spatial attention within a 3-D viewer-centered spatial representation.

Effect of template complexity on visual search and dual-task performance.

Even dissimilar tasks interfere with one another when done together. We used visual search to examine the underlying cause of such interference. In many models, visual search is a process of biased competition controlled by a template describing the target to be sought. When the display is processed, matching against this template guides attention to the target. We show that increasing template complexity increased interference with a dissimilar concurrent task, story memory. This result was independent of reaction time: Increases in template complexity were associated with no increase in search time in Experiment 1 and with a decrease in search time in Experiment 2. The results show that the dual-task demands of visual search reflect the complexity of the template used in task control, and that this factor can be isolated from other sources of difficulty.