Is there evidence for non-conscious processing in working memory?

Abstract

Working Memory can be conceived as a mental workspace holding and manipulating a limited amount of recently acquired information for a limited time. Some theories assume that it is tightly coupled with Consciousness (e.g., Baars & Franklin, 2003), commonly defined in experimental studies as the ability to report the content of perception or of memory. Other theories posit that working memory includes cognitive processes of which participants are not conscious (e.g., Soto et al., 2011; Logie, 2016), and can be activated without conscious intention (Hassin et al., 2009). Here, I describe experimental work designed to investigate the possible implicit activation of working memory without awareness. Importantly, participants were not only unaware of the stimuli that might be held in working memory, but also unaware that such stimuli were being presented at all. They were asked to guess which one of four cards presented on the screen was the winning one; one card was subliminally primed before a retention interval (which could vary between 500, 1000, 2000 and 5000 ms). The winner, on each trial, was chosen from amongst four blue cards, one of which had been primed, without awareness, by a card of a different colour (red or green) using Continuous Flash Suppression or Backward Masking. Bayesian and classical analyses from nine experiments mostly support the null hypothesis, thus indicating that working memory was not engaged in performing this task. Two conceptual replications and four exact replications of the original study by Soto et al. (2011), also failed in reproducing the original results. In conclusion, this collection of fifteen experiments encompassing different manipulations shows the absence of non-conscious WM retention, questioning the generalisability of previous studies showing non-conscious WM.