Constrainted but robust feature integration in visual working memory

Visual working memory (VWM) could actively integrate spatio-temporal discrete information into unified and structured representations. However, it remains unknown whether the integration in VWM occurs on the object level or feature level. The current study addressed this issue by examing the integration on the orientation dimension while manipulating the heterogeneity of the color dimension on the same objects. In three experiments, participants were instructed to remember the sequentially presented orientations with potential grouping cues (i.e., collinearity) during VWM maintenance. The results showed that the heterogeneity of task-irrelevant colors could not significantly affect the integration effect of orientations (Experiment 1), which might be due to the fact that the irrelevant colors were intentionally discarded in VWM (Experiment 2). As a contrast, when the color became task-relevant (Experiment 3), the integration of orientations could still be formed but was significantly affected by inconsistent colors. These results indicated that feature-based VWM integration was robust, but could also be modulated by the object structure, aligning well with the hierarchically feature-based representational model of VWM.