Meaningful objects are privileged in working memory: better incidental memory of recognizable relative to unrecognizable objects

Previous research has shown that when participants are confronted with a surprise trial to report a previously irrelevant visual feature (e.g., orientation in a color memory task), they have little information about that feature, suggesting that task-irrelevant features are often not well encoded incidentally (Tam & Wyble, 2022). Other recent work has shown that visual working memory for simple features, such as color, can be improved when memorizing these features as part of meaningful objects (Chung et al., 2022). Can incidental memory of task-irrelevant features also improve if those features are meaningful? Participants (N = 30 for each condition) performed a color working memory task where one stimulus appeared for 800 ms followed by a delay period of 1,000 ms and a 4-alternative-forced-choice color task. In the meaningful stimulus condition, colors were shown as silhouettes of various objects; in the non-meaningful stimulus condition, colors were shown as unrecognizable scrambled versions of the same objects. After 52 color-report trials, participants were surprised with an identity 4-AFC task in which they had to report which object they saw on the last trial (irrespective of color). We found that participants had higher performance on the surprise trial for recognizable silhouettes compared to unrecognizable scrambled shapes. When participants repeated the same identity trial subsequent to the initial surprise trial, we observed no difference in performance across the two conditions, indicating that these effects were specific to the incidental memory of object identity. The same effect was replicated with a shorter encoding time (200 ms) in a new sample (N=60). Overall, our results demonstrate that meaningful object identities are incidentally remembered at a higher accuracy than unrecognizable shapes. This adds to recent evidence indicating a privileged role for meaningful objects in visual working memory.