Abstract
In simple visual search tasks, repetition of spatial context reduces RTs when the context is predictive of target location (Chun & Jiang, 1998). This contextual cueing effect is often considered to be the result of a highly automatic and efficient learning process. People seem to learn even about parts of the spatial context that they have been explicitly asked to ignore (Vadillo et al., 2020). But, are participants really able to ignore some elements as requested by the experimenter? To clarify this issue, we run a series of visual search experiments in which we kept the number of relevant items constant but varied the number of irrelevant items. Eye movements were recorded to obtain a direct measure of focal attention to the different elements. In each trial, participants had to find a rotated T among rotated Ls. In the first experiment 8 distractors had the same color as the target (relevant distractors), while either 4 or 16 distractors had a different color (irrelevant distractors). Half of the configurations were repeated along the experiment, intermixed with newly generated configurations. RTs replicated contextual cueing effects, but also showed that it took longer to find the target when more irrelevant distractors were presented. Analysis of eye fixations over the whole experiment showed that about 12% of all fixations were on relevant distractors and 6% on irrelevant distractors. In the second experiment 8 relevant distractors appeared surrounded by 4, 8, 16 or 32 irrelevant distractors. Configurations of relevant distractors were repeated (32 different configurations, 8 repetitions), but irrelevant distractors were always placed randomly. Results showed search facilitation due to repetition, but also that the number of irrelevant distractors clearly affected performance. Specifically, fixations on irrelevant distractors steadily increased over conditions. These results suggest that selective attention cannot completely suppress the effect of irrelevant items.