Awareness & Perception in Rapid Serial Visual Presentation

This thesis explores the subjective experience of targets in rapid serial visual presentation (RSVP), an experimental paradigm where visual stimuli are displayed in rapid succession. In RSVP, items appear on the screen so briefly that not every item in the stream can be encoded reliably. Thus, it allows observation of conscious experience at the fringe of perception. The Attentional Blink (AB) - an effect in which an RSVP target is likely to be missed if it follows a fully processed first target - has been used in order to manipulate the accuracy of item identification by varying the target separation and presentation speed. The main focus of studies using RSVP presentation to make inferences about conscious perception has been the question of whether conscious perception is all-or-none or gradual. We initially present some thoughts on the suitability of the AB paradigm for answering this question. Not much is known about the effect of different variables in the paradigm on subjective experience, and it is possible that AB mechanisms affect experience quite differently from other paradigms, limiting the generalisability of findings derived from work within the AB paradigm. Based on this, we follow two lines of evidence: First, we explore the possibility of finding gradations in subjective visibility of targets measured on ratings scales and in the response of the electroencephalogram using a simple single target RSVP. Second, we investigate the effect of target separation and perceived order on this subjective experience in the AB paradigm. Our results indicate that items in single-target RSVP can be perceived in a graded manner, with possible indications of a non-linear jump in brain activity between not-seen and seen items. Regarding subjective experience when separation of two targets is varied, we find a disconnect between accuracy and visibility of the second target when in close proximity to the first, showing relatively low subjective experience considering the high report accuracy. Target separation also affects the number of order confusions, which we find to reduce target visibility under specific conditions. These results add to our understanding of how targets are perceived in RSVP and have implications for research into conscious perception