Abstract
Reorientation of visuospatial attention is associated with cost. This holds true not only for attentional shifts within a fronto-parallel plane but also when attention is shifted between stereoscopic depth planes. These effects are often observed within experimental trials. In the present series of experiments participants performed a visual search task in two distinct depth planes (near and far depth plane) that required spatial reorientation across trials. The search array was randomly displayed in one depth plane while there was no predictive information regarding the target depth plane. Due to the sequence of events two trial types were defined: Repetition trials (target depth plane equal to previous trial) and switch trials (target depth plane different than previous trial). Furthermore, in one experimental condition a valid or invalid spatial cue was displayed in the same depth plane as the target or in the opposite plane in order to increase the spatial character of the task. It was hypothesized that faster responses will be observed when attention remains in the same depth plane (repetition trials). The results were ambiguous with regard to the comparison of repetition and switch trials. In Experiment 1 no differences between both conditions were observed. In contrast, introducing a spatial cue (Experiment 2) did not only cause a strong validity effect. Reaction times were also significantly shorter in repetition trials and in trails displayed in the near depth plane. Likewise, fewer errors were associated with repetition trials. Apparently, participants orient their attentional focus to distinct depth planes as long as spatial information proves beneficial for response execution. The results also suggest that this process may be performed along an egocentric gradient through space and that attention (incidentally) remains in depth planes that were previously task relevant.
Acknowledgement: This work was supported by the Research Training Group 1855, founded by the German Research Foundation (DFG) and the Center of Excellence for Logistics and IT, founded by the Ministry of Innovation, Science and Research of the State of North Rhine- Westphalia, Germany.