An assessment of fixed-capacity models of visual working memory

Abstract

Visual working memory is often modeled as having a fixed number of slots. We test this model by assessing the receiver operating characteristics (ROC) of participants in a visual-working-memory change-detection task. ROC plots yielded straight lines with a slope of 1.0, a tell-tale characteristic of all-or-none mnemonic representations. Formal model assessment yielded evidence highly consistent with a discrete fixed-capacity model of working memory for this task.

Fig. 1.

Experimental paradigm and fixed-capacity model predictions. (A) Structure of a trial in the experiment. The squares and masks in the experiment varied in color rather than gray scale. (B) Selective influence predictions for ROC plots. The predicted points are constrained to be at the intersections of equal-sensitivity and equal-bias lines.

Fig. 2.

Results. (A) ROC results (2D error bars) and predictions (lines and small points) from the five-parameter fixed-capacity model. Error bars denote standard errors of means in each measure. (B) Scatter plot of capacity in the eight-square arrays as a function of that in the five-square arrays. Filled points indicate participants for whom fixed capacity may not be rejected in favor of variable capacity. Open points are exceptions; see text.