Dissociating Contents of Consciousness from Contents of Short-Term Memory

The contents of consciousness and of short-term memory are hard to disentangle. As it seems intuitive that we represent attended objects in short-term memory and in experience, to many, it also seems intuitive to equate this content.
Here we investigated memory resolution for orientation of a probed target in combination with a conscious evaluation of the experienced stimulus using the Perceptual Awareness Scale (PAS; Ramsøy & Overgaard, 2004). Observers were trained to report how they experienced a visual stimulus on a four-point scale representing their experience from “no experience” to a “clear experience” of a probed target. To assess memory resolution we used a Landolt-variation on the visual short-term memory (VSTM) resolution paradigm (e.g. Wilken & Ma, 2004). Set-sizes in the memory display were varied between 1, 2, or 4 elements.
With increasing set-size we found that both the guessing parameter and the standard deviation increased, replicating patterns seen in more traditional paradigms using colors (see for example Bays, Catalao, & Husain, 2009). Moreover, we also find a decrease in guessing and standard deviation across PAS scores, showing that the resolution of content in VSTM is correlated with how it is consciously perceived by an observer. However, if we analyze the data across individual PAS scores and set-sizes, a different pattern emerges; across PAS scores we find that people are still affected by set-size in a systematic fashion. Controlling for target confusability we demonstrate that the effect cannot be explained by observers’ responses to distractors, which leads us to conclude that contents of consciousness and VSTM may correlate, but are in fact not identical.