This thesis investigates the relationship between consciousness, attention, and experience in the periphery of the visual field. I argue that there are some visual experiences that lack content in the sense of lacking accuracy conditions and also in stronger senses. I define subjective space as the manifold constituted by the various factors that modulate awareness of an object including attention, eccentricity, eccentricity-relative spacing, and so on. The subjective periphery is that area of subjective space in which no objects or properties are experienced. It is subjectively peripheral experiences that lack content. In part my argument depends on claims about phenomenal experience. I establish these by considering a variety of introspective and experimental phenomena related to attention and conscious awareness and extracting a set of data that are neutral with respect to the theories that might explain them. I pursue an argument to the best explanation, refuting three popular explanations and championing my own. The first is that endorsed by Dennett (1991) and Noë (2004). They each claim that our experience of phenomenal character in the subjective periphery is an illusion (or a defeasible illusion). The second explanation, endorsed by Block (2007), is that there is phenomenal experience and content in the periphery but no cognitive awareness of it; thus, reports and other indicators of content fail. The third explanation is that there are indeterminate or general contents in the subjective periphery. This is the representationalist’s explanation. The fourth explanation, my explanation, is that there are in fact experiences that do not present objects or properties at locations in the subjective periphery, and that consequently lack content. I argue that this is the best explanation of the data since the others either fail to account for all the neutral data, can be shown to be false for independent reasons, or both. I also defend a number of distinct conclusions that nevertheless strengthen the main line of argument. For example, I consider the view that all attention is conscious, which helps to salvage the reliability of introspection as a method of investigating attention and experience.

Thesis (Ph.D.)--Australian National University, 2003.

Can the brain register the emotional valence of brief exposures of complex natural stimuli under conditions of forward and backward masking, and under conditions of attentional competition between foveal and peripheral stimuli? To address this question, three experiments were conducted. The first, a behavioural experiment, measured subjective valence of response (pleasant vs unpleasant) to test the perception of the valence of natural images in brief, masked exposures in a forward and backward masking paradigm. Images were chosen from the International Affective Picture System (IAPS) series. After correction for response bias, responses to the majority of target stimuli were concordant with the IAPS ratings at better than chance, even when the presence of the target was undetected. Using functional magnetic resonance imaging (fMRI), the effects of IAPS valence and stimulus category were objectively measured on nine regions of interest (ROIs) using the same strict temporal restrictions in a similar masking design. Evidence of affective processing close to or below conscious threshold was apparent in some of the ROIs. To further this line of enquiry, a second fMRI experiment mapping the same ROIs and using the same stimuli were presented in a foveal (‘attended’) peripheral (‘to-be-ignored’) paradigm (small image superimposed in the centre of a large image of the same category, but opposite valence) to investigate spatial parameters and limitations of attention. Results are interpreted as showing both valence and category specific effects of ‘to-be-ignored’ images in the periphery. These results are discussed in light of theories of the limitations of attentional capacity and the speed in which we process natural images, providing new evidence of the breadth of variety in the types of affective visual stimuli we are able to process close to the threshold of conscious perception.