The development of retro-cue benefits with extensive practice: Implications for capacity estimation and attentional states in visual working memory

Abstract

Accessing the contents of visual short-term memory (VSTM) is compromised by information bottlenecks and visual interference between memorization and recall. Retro-cues, displayed after the offset of a memory stimulus and prior to the onset of a probe stimulus, indicate the test item and improve performance in VSTM tasks. It has been proposed that retro-cues aid recall by transferring information from a high-capacity memory store into visual working memory (multiple-store hypothesis). Alternatively, retro-cues could aid recall by redistributing memory resources within the same (low-capacity) working memory store (single-store hypothesis). If retro-cues provide access to a memory store with a capacity exceeding the set size, then, given sufficient training in the use of the retro-cue, near-ceiling performance should be observed. To test this prediction, 10 observers each performed 12 hours across 8 sessions in a retro-cue change-detection task (40,000+ trials total). The results provided clear support for the single-store hypothesis: retro-cue benefits (difference between a condition with and without retro-cues) emerged after a few hundred trials and then remained constant throughout the testing sessions, consistently improving performance by two items, rather than reaching ceiling performance. Surprisingly, we also observed a general increase in performance throughout the experiment in conditions with and without retro-cues, calling into question the generalizability of change-detection tasks in assessing working memory capacity as a stable trait of an observer (data and materials are available at osf.io/9xr82 and github.com/paulzerr/retrocues). In summary, the present findings suggest that retro-cues increase capacity estimates by redistributing memory resources across memoranda within a low-capacity working memory store.

Keywords: Attention; Change-detection; Retro-cues; Sensory memory; Visual working memory; Working memory capacity.

Fig. 1

Graphical representation of the investigated hypotheses, which depicts two different ways in which information could be maintained in the visual system, and how reallocation of VWM resources following a retro-cue could act on these representations to improve performance in a change-detection task. The y-axis represents the amount of attention (i.e., the memory resource underlying VWM) an item received. The bars on the left represent memory items in sensory memory or LTM, which can be cued (and accessed) with a retro-cue, but which are not subject to the same resource limitation as VWM. The bars on the right represent weakly and strongly attended items represented in low-capacity VWM. The green, dashed line represents the amount of VWM resources required for a memory object to be reportable in a change-detection task. A weakly attended item in VWM would not be reportable due to visual interference by the memory probe. The arrows represent how retro-cues would act on the different memory representations and increase capacity estimations under the multiple-store hypothesis (H₁; blue arrow) and single-store hypothesis (H₂; red arrow). (Color figure online)

Fig. 2

Trial layout. Sizes and colors are stylized in favor of visualization. First, a memory stimulus is displayed, consisting of 12 bars in one of four orientations. After a delay period, during which only the fixation dot and 12 placeholder dots are visible, a noise mask is presented. In the retro-cue condition, a cue in the form of a small circle is then shown on one of the placeholder dots, which indicates the location of the upcoming target to be recalled. This is followed by a delay period and a memory probe display, consisting of the same 12 oriented bars, one of which has a 50% chance of being rotated by 90°. This target is indicated by a small circle, identical to the retro-cue. In the post-cue condition, instead of a cue display, the memory probe display is shown immediately after the noise mask, and simultaneously with the probe array

Fig. 3

Main results for a moving average window size of 200 trials. Result graphs for a wide range of window sizes can be obtained in the online materials (osf.io/9xr82) and an animated version (gif) at (osf.io/wqz8g). a Accuracy in the post-cue and retro-cue conditions as moving averages. Thin lines indicate results from individual subjects. Thick lines indicate the estimated mean accuracy for each trial time. Shaded areas indicate estimated standard error. b Retro-cue benefit (retro-cue accuracy minus post-cue accuracy) and model fits. c Effect size and evidence for an effect size greater than zero for each trial time. The solid horizontal line indicates BF = 1 and the dashed horizontal line indicates BF = 3, a popular threshold for “evidence worth considering”

Fig. 4

Individual observer data as percent correct, split into two bins per experimental session. All observers demonstrated a retro-cue benefit after some time