Inattentional blindness refers to a failure to detect visible objects when attention is engaged in a task. Despite the central role for attention implied by its name, there is surprisingly little evidence that inattentional blindness indeed results from inattention. In this thesis I provide such evidence in demonstrating that rates of inattentional blindness critically depend on the extent to which a relevant task exhausts attentional capacity (under high perceptual load) or leaves spare capacity (under low perceptual load) for determining awareness of task-irrelevant stimuli. This was found when load was increased by requiring a more subtle line-length judgment in the traditional inattentional blindness cross-task, or by increasing the number of items in a visual search task. Further experiments generalised the effects of perceptual load on awareness across simple shapes and meaningful objects, and for irrelevant stimuli appearing in the periphery and at fixation. By contrast, upright (but not inverted) faces reached awareness regardless of the level of perceptual load in the relevant task. These findings are consistent with previous behavioural perceptual load studies using reaction time (RT) measures of task-irrelevant processing (Lavie, 1995 Lavie, Ro & Russell, 2003 see Lavie, 2005 for review) and support the conclusion that perceptual load determines conscious awareness. The experiments also found no advantage for awareness at fixation versus awareness at the periphery, highlighting a potential dissociation between awareness measures and distracter effects on RTs (which have previously shown such an advantage, Beck & Lavie, 2005). Finally, this thesis presents a preliminary investigation of the development of awareness as measured by rates of inattentional blindness under different levels of task load in children and in adults. Results demonstrated a clear pattern of increasing awareness with increasing age, and lend partial support to the notion that the development of attentional capacity underlies this trend in awareness.

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Recent behavioural and neural research suggests that awareness is intimately related to top-down cognitive functions such as attention. Here I present a characterization of this relationship, guided by Lavie's load theory. Load theory proposes that perception has limited capacity but proceeds automatically on all stimuli (whether relevant to the task at hand or not) until capacity is exhausted, and that the allocation of processing resources to certain stimuli (rather than to other, competing ones) is guided by executive control functions such as working memory. The theory predicts that increasing the perceptual load of a task will consume capacity, therefore reducing processing of stimuli external to that task it also predicts that increasing working memory load will impair executive control, leading to increased processing of salient ignored stimuli. Here I show that these predictions hold not only for indirect measures of perceptual processing, as has been demonstrated previously, but also for visual awareness - the subjective experience of seeing and being able to report the nature of a visual stimulus. I find that under high perceptual load, observers become less aware of the very presence of other stimuli, even when these stimuli are fully expected and serve as targets. I also show that perceptual load affects the temporal resolution of visual awareness - under high load, the ability to detect a temporal pattern (luminance flicker) is reduced, leading to a subjective percept of steady illumination. In a neuroimaging study, I show that subjective awareness of flicker is associated with activity in frontal and parietal brain regions previously associated with attention and awareness. Next, I investigate the role of executive control in visual awareness by examining the effect of working memory load on binocular rivalry, a fundamental form of visual competition. I find that high working memory load reduces dominance durations in rivalry, suggesting that working memory may serve to maintain perceptual biases during competitive interactions in visual awareness. Finally, I use Transcranial Magnetic Stimulation to establish a causal role for the previously described right parietal involvement in the control of binocular rivalry. This research therefore indicates that top- down cognitive and neural mechanisms are involved in determining whether visual stimuli will reach awareness, and in shaping the subjective nature of the experience such stimuli evoke.

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The phenomenon of boredom appears to be very prevalent in our society, and in particular is encountered by occupational therapists in their practice. A substantial body of literature both from the arts and the sciences indicates that boredom proneness is linked to emotional distress, and seems to be associated with a wide range of dysfunctional behaviour. Yet despite this boredom is poorly understood, and has no accepted definition. Little research has been carried out on the subject, and there is almost no indication of how this apparently problematic experience can be dealt with. From a pragmatic position, a study using mixed methods was conducted to investigate the nature of being bored. In the first stage an interpretive phenomenological design was employed with in-depth interviews to explore the antecedents to boredom, describe the experience including any stages, and to find out if and how people attempted to overcome boredom. Participants were 10 members from the general population. Findings indicated that boredom was experienced in a similar way by all, with feelings of restlessness, lethargy, dissatisfaction and inability to focus on any one activity. Antecedents and strategies varied, but no stages were identified. Following several phases of interpretation and analysis a hypothesis was unexpectedly generated. It seemed that lack of sustained attention might be the most important factor in producing boredom so the second stage was designed to test this theory. A correlation between two measures, the Boredom Proneness Scale and the Mindful Attention Awareness Scale, was carried out on a sample of 356 university students. There was a moderate significant correlation between the two scales (r= -0.440, p<0.01). Both stages of this study to some extent support the idea that boredom might be associated with attentional difficulty. It is more likely however that boredom is associated with a lack of mindfulness, as this concept includes attitudinal as well as cognitive factors. Mindfulness is an ability to be fully aware of the present moment, without judgement, whereas boredom appears to be a state of inattention to the present moment, accompanied by dissatisfaction. Further research is needed to investigate this possibility from both positivist and constructivist perspectives. If the two phenomena are at opposite ends of a continuum, it might be possible to overcome a propensity to boredom through learning how to be more mindful. Occupational Therapists could promote more mindful ways of doing.