On the Relationship between Visual Attention and Perceptual Awareness

Abstract

Selectively attending to what is important in the environment while ignoring less important information is strongly correlated with what is experienced subjectively. Despite this seemingly obvious relationship between what is attended and what is perceived, there is a long-standing debate regarding whether attention and awareness are functionally related. While some have suggested that the two processes are identical, others have argued that they can be dissociated, either singularly (i.e., one process depends on the other) or doubly (i.e., the two processes can act independently). The overarching aim of my thesis was to investigate the relationship between visual attention and awareness, by combining behavioral methods, electroencephalography (EEG) and computational modeling. The thesis is divided into five chapters. In Chapter 1, I review previous literature related to the debate in relation to the no dissociation, single dissociation, and double dissociation views. In doing so, I highlight that the conclusions made about the way attention and awareness relate depend on the task or physical stimulation differences between conditions. In Chapter 2, I endeavored to replicate a study by van Boxtel, Tsuchiya, and Koch (2010a), who reported a double dissociation between attention and awareness using a perceptual adaptation task in which participants' perceptual awareness and visual attention were manipulated independently. van Boxtel et al. (2010a) found that participants' awareness of an adapting stimulus increased afterimage duration, whereas attending to the adaptor decreased it. Consistent with van Boxtel et al. (2010a), I found that afterimage duration was reliably increased when participants were aware of the adapting stimulus. In contrast to van Boxtel et al., however, I found that attention to the adaptor also increased afterimage duration, suggesting that attention and awareness had the same-rather than opposing-effects on afterimage duration. This failure to replicate suggests caution in using this specific approach to support the argument that attention and awareness are dissociable processes. In Chapter 3, across three experiments, I investigated behavioral and EEG responses to examine whether enhancement of goal-relevant stimuli and suppression of goal-irrelevant stimuli arise even when stimuli are masked from awareness. I used a feature-based spatial cueing paradigm in which participants searched four-item arrays for a target in a specific color. Immediately before the target array, a non-predictive cue display was presented in which a cue matched or mismatched the searched-for target color, and appeared either at the target location (valid) or another location (invalid). Cue displays were masked using continuous flash suppression, so that participants were unaware of them on roughly half the trials. The EEG data revealed that target-colored cues produced robust signatures of spatial orienting and distractor-colored cues produced a signature of suppression. Critically, these signatures occurred for bot...