The conjunction of non-consciously perceived object identity and spatial position can be retained during a visual short-term memory task.

Fredrik Bergström,Johan Eriksson

doi:10.3389/fpsyg.2015.01470

Abstract

Although non-consciously perceived information has previously been assumed to be short-lived (< 500 ms), recent findings show that non-consciously perceived information can be maintained for at least 15 s. Such findings can be explained as working memory without a conscious experience of the information to be retained. However, whether or not working memory can operate on non-consciously perceived information remains controversial, and little is known about the nature of such non-conscious visual short-term memory (VSTM). Here we used continuous flash suppression to render stimuli non-conscious, to investigate the properties of non-consciously perceived representations in delayed match-to-sample (DMS) tasks. In Experiment I we used variable delays (5 or 15 s) and found that performance was significantly better than chance and was unaffected by delay duration, thereby replicating previous findings. In Experiment II the DMS task required participants to combine information of spatial position and object identity on a trial-by-trial basis to successfully solve the task. We found that the conjunction of spatial position and object identity was retained, thereby verifying that non-conscious, trial-specific information can be maintained for prospective use. We conclude that our results are consistent with a working memory interpretation, but that more research is needed to verify this interpretation.

Highlights

Non-consciously perceived information can be processed at all levels of the visual system (Rees et al, 2002; Kouider and Dehaene, 2007), and influence executive functions (Lau and Passingham, 2007; van Gaal et al, 2010)
To examine the relative contributions of spatial position, object identity, and the conjunction of both in driving the non-conscious delayed match-to-sample (DMS) d′ effect, we looked at the proportion of trials within each of the categories full match, object match, spatial match, and non-match, where participants responded “match.” In short, we compared hit rate and the false alarm rates when only object identity matched, only spatial position matched, and when neither matched
The participants were instructed to only remember the spatial position, it is possible that face identity and/or emotion information contributed to performance

Summary

Introduction

Non-consciously perceived information can be processed at all levels of the visual system (Rees et al, 2002; Kouider and Dehaene, 2007), and influence executive functions (Lau and Passingham, 2007; van Gaal et al, 2010). It is less clear for how long non-consciously perceived information can be retained and influence behavior. Bar and Biederman (1998, 1999) found behavioral evidence of non-consciously encoded visual repetition priming effects on naming tasks after 15–20 min, and Reber et al (2012) found that repeatedly presented masked word-pairs could influence decision-making 1 min later, and that hippocampal BOLD signal change at encoding predicted the outcomes. Bar and Biederman (1998, 1999) found behavioral evidence of non-consciously encoded visual repetition priming effects on naming tasks after 15–20 min, and

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Conclusion