Probabilistic retro-cues do not determine state in visual working memory

Abstract

The effective use of our capacity-limited visual working memory (VWM) requires mechanisms that govern how it represents information. Validly cueing an item in VWM after encoding, for instance, enhances memory performance for that item and biases its state in VWM, bringing its representation to an active state such that attentional selection is biased towards perceptually similar inputs. Critically, when the retro-cue is less than 100% valid (i.e., probabilistic rather than deterministic), the effect of the cue on memory performance varies. Here we investigated whether deterministic and probabilistic retro-cues also differ in their influence over item state in VWM. Participants encoded two colored squares, and a retro-cue indicated which item was most likely to be probed in a subsequent memory test. Across blocks, we manipulated cue validity to be deterministic (100% valid) or probabilistic (70% valid). On a subset of trials, no memory probe was presented and the trial ended with a visual search task in which a colored distractor-matching the cued memory item, the non-cued item, or neitherwas presented. Predictably, in the deterministic condition, the presence of a singleton distractor matching the cued item reliably slowed reaction times during visual search. In the probabilistic condition, however, there were no differences in reaction times when the singleton matched the cued item or the non-cued item, despite a reliable benefit to memory performance on valid memory trials. We suggest that, while probabilistic retro-cues improve memory of the cued item, they are not sufficient to bias its state in VWM.

Distinct prioritization of visual working memory representations for search and for recall

“…Despite reliably influencing memory performance in the present study, items in VWM identified as high priority for an upcoming memory test consistently failed to bias attentional selection to a greater degree than those identified as low priority during visual search for a static target − a search condition that is conducive to allowing a memory item to occupy the active position (Carlisle et al, 2011;Woodman, Luck, & Schall, 2007). It has, however, repeatedly been shown that when only one memory item is maintained for later use, that item does bias attention during visual search for a static target (Olivers et al, 2006;van Moorselaar et al, 2014; but see Beck, Hollingworth, & Luck, 2012), and we have similarly shown that a memory item that is retroactively cued as the object of the upcoming memory test with 100% validity also biases attention during visual search (likely due to the removal of the non-cued item from memory; Dube et al, 2018). Thus, when more than a single item is held in memory, it is not simply the distribution of VWM resources across items that determines which items bias attention-there is something inherently different about prioritizing an item for use as a search template that allows that item to interact with attentional selection.…”

“…This work highlights an important point about the use of probabilistic cues to bias item state in VWM (i.e., cues that are less than 100% valid). Indeed, in recent work we have shown that, despite being used in previous research as a means to influence item state, probabilistic retro-cues are insufficient to activate the cued item in VWM (Dube et al, 2018). Despite reliably influencing memory performance in the present study, items in VWM identified as high priority for an upcoming memory test consistently failed to bias attentional selection to a greater degree than those identified as low priority during visual search for a static target − a search condition that is conducive to allowing a memory item to occupy the active position (Carlisle et al, 2011;Woodman, Luck, & Schall, 2007).…”

“…As such, it is unclear whether their cues actually affected priority for search, or if both memory items were represented in an accessory state. Indeed, given that their cue was probabilistic in nature, it is likely that it did not affect priority for search (see Dube, Lumsden, & Al-Aidroos, 2018). Accordingly, in the present study we adjusted the paradigm used by Hollingworth and Hwang to address this limitation, and directly tested whether cueing an item to be remembered more precisely also causes that item to bias attention.…”

Memory-driven capture occurs for individual features of an object

“…Does visual input matching feature information that was encoded into WM but is no longer relevant still grab external attention? (see 36,37,[56][57][58] for evidence of this at the object level). To answer this question, we asked people to memorize the color and orientation of an isosceles triangle.…”

Addressing properties and limitations of flexible resource allocation in visual short-term memory

“…Recent evidence from a study by Dube, Lumsden, and Al-Aidroos, (2018) found that a single probabilistic retro-cue valid at 70% could improve accuracy of change detection to a similar extent as the 100% valid "deterministic" cued item; critically, however, they showed evidence that the item cued with 70% validity did not bias attention in a subsequent visual search task, whereas the 100% validly cued item did. This evidence may suggest that retro-cueing multiple items is ineffective because multiple (retro-cued) items are not maintained in the focus of attention.…”