A common feature improves guidance efficiency during hybrid search

Imagine searching for all the ingredients for a cake at the grocery store. This type of "hybrid" visual search is common in daily life and involves searching for many items from memory at once. Hybrid search involves two stages: visual search for possible targets to select, and then search through memory for a matching target. While we can successfully seek numerous objects concurrently, RT is relatively slow and increases logarithmically with the number of items in the target set. In two studies (N = 147) we tested the hypothesis that having a common feature across targets such as the color "red" (e.g., if searching for apples, strawberries, and tomatoes) will facilitate hybrid search by reducing the target template for visual guidance into one-dimensional "common feature" search. In experiments 1a and 1b, we confirmed that color, as a common feature among targets, was used to guide attention during visual search, as shown by slower RTs when a "common feature" distractor was present. In experiment 2, participants memorized twenty "target" objects in various colors (red, blue, yellow, green) and categories (fruit, toys, animals, furniture, flowers). Before each test trial, a target list of 1, 3, or 5 items was shown. Items were either color-similar (e.g., all red objects) or mixed. Only one of the possible targets was present on a single trial. We found main effects of common color and target set size, but no interaction. While the logarithmic increase in RT due to memory search set size appeared to remain, RTs in the common color condition were overall shorter and did not show serial position effects related to the target list. Finally, individuals that self-reported using common feature for search were faster overall, suggesting it is a strategic shortcut that reduces working memory load and maintenance.