Mixing and mingling in visual working memory: Inter-item competition is feature-specific during encoding and feature-general during maintenance

Abstract

Visual working memory (WM) is a central cognitive ability but is capacity-limited due to competition between remembered items. Understanding whether inter-item competition depends on the similarity of the features being remembered has important implications for determining if competition occurs in sensory or post-sensory stages of processing. Experiment 1 compared the precision of WM across homogeneous displays, where items belonged to the same feature type (e.g., colorful circles), and heterogeneous displays (e.g., colorful circles and oriented bars). Performance was better for heterogeneous displays, suggesting a feature-specific component of interference. However, Experiment 2 used a retro-cueing task to isolate encoding from online maintenance and revealed that inter-item competition during storage was not feature-specific. The data support recent models of WM in which inter-item interference - and hence capacity limits in WM - occurs in higher-order structures that receive convergent input from a diverse array of feature-specific representations.

Keywords: Sensory recruitment hypothesis; Visual working memory; Working memory interference.

Fig. 1

Procedure and conditions for Experiment 1a. Participants saw a display of objects, followed by a delay, and then an unspeeded report period (left). We used set sizes 1, 2, and 4, and set sizes 2 and 4 could be homogeneous or heterogeneous (right)

Fig. 2

Main results of Experiment 1a. Results are shown separately for trials where participants reported color (left) and orientation (right). Bar plots quantify the circular standard deviation of the error distribution for each set size and display condition, and error bars represent the standard error of the mean

Fig. 3

Histograms of response errors for set size 2, homogeneous trials (Experiment 1a). Response error plotted with respect to the probed item and with respect to the unprobed item

Fig. 4

Procedure and conditions for Experiment 1b. Trial structure (left) and example displays for homogeneous colors (top), homogeneous orientations (middle), and heterogeneous displays with two each of colors and orientations (bottom)

Fig. 5

Main results for Experiment 1b. Results are shown separately for trials where participants reported orientation (left) and color (right)

Fig. 6

Example displays for Experiment 2. This diagram omits conditions that differed only in the feature probed for report (e.g., heterogeneous displays where a color and orientation are retro-cued)

Fig. 7

Results for Experiment 2 homogeneous trials. Results are shown separately for trials where participants reported orientation (left) and color (right)

Fig. 8

Results for Experiment 2 trials with set size 1 or homogeneous retro-cue conditions. In this visualization, we kept retro-cue condition constant (retro-cue only colors, or only orientations) and visualized display condition. Results are shown separately for trials where participants reported orientation (left) and color (right)

Fig. 9

Results for Experiment 2 trials with heterogeneous displays. In this visualization, we kept display condition constant (two colors and two orientations) and visualized retro-cue condition. Results are shown separately for trials where participants reported color (left) and orientation (right)