A two-level hierarchical framework of visual short-term memory

The voluntary utilization of visual working memory

While a vast amount of research has focused on understanding the capacity limits of visual working memory (VWM), little is known about how VWM resources are employed in unforced behavior and how they correlate with individual capacity constraints. We present a novel, openly available, and easy-to-administer paradigm enabling participants to freely utilize their VWM capacity. Participants had to reconstruct an array of colored squares. In each trial, they were allowed to alternate between the memory array and the reconstruction screen as many times as they wished, each time choosing how many items to reconstruct. This approach allowed us to estimate the number of utilized items, as well as the accuracy of the reconstruction. In addition, VWM capacity was measured using a change detection task. In two experiments, we show that participants tend to under-utilize their VWM resources, performing well below their capacity limits. Surprisingly, while the extent to which participants utilized their VWM was highly reliable, it was uncorrelated with VWM capacity, suggesting that VWM utilization is limited due to strategic considerations rather than capacity limits.

The mechanisms of selective attention in phenomenal consciousness

In three experiments we investigated the effects of selective attention in iconic memory and fragile-visual short-term memory (VSTM), which have been related to phenomenal consciousness. We used a novel retro-cue paradigm with different delays (early vs late) and object priorities (high vs equal vs low), to investigate (a) attentional costs and benefits and the role of (b) bottom-up factors and (c) fragile-VSTM in feature-based attentional selection. Experiment 1 showed that attentional costs modulate visual maintenance at longer delays, while Experiment 2 showed that by reducing the time exposure of the memory array from 250 ms to 100 ms, as a bottom-up factor, participants were not able to select the objects based on their priorities. Finally, Experiment 3 showed that a pattern mask presented before the transfer in visual working memory, attenuates the overall performance while preserving the priority effect. The implications for phenomenal consciousness before conscious access are discussed.

Event-based encoding of biological motion and location in visual working memory

We make use of discrete yet meaningful events to orient ourselves to the dynamic environment. Among these events, biological motion, referring to the movements of animate entities, is one of the most biologically salient. We usually encounter biological motions of multiple human beings taking place simultaneously at distinct locations. How we encode biological motions into visual working memory (VWM) to form a coherent experience of the external world and guide our social behaviour remains unclear. This study for the first time addressed the VWM encoding mechanism of biological motions and their corresponding locations. We tested an event-based encoding hypothesis for biological motion and location: When one element of an event is required to be memorised, the irrelevant element of an event will also be extracted into VWM. We presented participants with three biological motions at different locations and required them to memorise only the biological motions or their locations while ignoring the other dimension. We examined the event-based encoding by probing a distracting effect: If the event-based encoding took place, the change of irrelevant dimension in the probe would lead to a significant distraction and impair the performance of detecting target dimension. We found significant distracting effects, which lasted for 3 s but vanished at 6 s, regardless of the target dimension (biological motions vs. locations, Experiment 1) and the exposure time of memory array (1 s vs. 3 s, Experiment 2). These results together support an event-based encoding mechanism during VWM encoding of biological motions and their corresponding locations.