Top-down instructions influence the attentional weight on color and shape dimensions during redundant search

Previous research showed that targets defined redundantly along both color and shape dimensions are found faster than those defined by only color or only shape. In redundant situations, target-distractor distinctiveness is a sum of distinctiveness along the two individual dimensions (Buetti et al., 2019). Xu et al. (2023) computationally showed that this composition is influenced by top-down factors: when participants were instructed to search for a target color in redundant search trials, they allocated more attentional weight to the color dimension (and less weight to the shape dimension) compared to when instructed to search for a target shape, which then impact their redundant search efficiency. However, Xu et al. (2023) did not confirm if participants adhered to the given instructions throughout the experiment. It's plausible that over time, participants recognized the consistent redundancy across dimensions, leading them to utilize both features in their search. Our study introduces a more robust top-down manipulation to address this potential shortcoming. In Experiment 1A-C, participants were instructed to search for a target color, while the target differed from distractors in either color, or both color and shape, with the two types of trials intermixed. Experiment 2A-C replicated this setup, focusing on shape. This design ensures that only the instructed dimension consistently indicated the target from trial to trial. We compared participants’ search efficiency on redundant trials (which were the same for Experiments 1 and 2) when they were instructed to rely on the color (Experiment1) or shape (Experiment2) dimensions. Results replicated previous findings, showing that people attended more the instructed dimension, which then determined the extent to which they utilized information from the given dimension in redundant search scenarios. Our study reaffirms the role of top-down influences in redundant search, highlighting how attentional weighting impacts the integration of distinctiveness signals from different visual dimensions.