No description available.

No description available.

No description available.

The proposed transcoding system consists of the spatial-resolution reduction and the temporal-resolution reduction method via visual attention model analysis. In the spatial domain, the visual attention model can be used to obtain the visual attention region. Then, the bitrate can be reduced since we can extract attention region of the original frame. The attention region conveys the same concept as that of the original frame. In the temporal domain, a frame skipping algorithm is proposed for reducing the temporal resolution to fit the channel target bitrate. The visual attention model is employed to measure the frame complexity in order to determine whether the frames should be skipped or not. Then, we can preserve the significant frames to avoid jerky effect. After combining with the motion vector composition algorithm, we can speedup the transcoding process with slight quality degradation.

Orienting processing resources towards a peripheral region of a display, by means of an exogenous cue, produces a biphasic effect on subsequent target detection. Intially response latency is facilitated, but increasing the SOA to 300 ms or greater results in slower detection, and this is known as the inhibition of return (IOR) effect. Initially this inhibitory effect was thought to bias attention against returning to a previously attended location but subsequent work demonstrated that it can also be associated with an object when motion is utilised to dissociate the two effects. This thesis reexamined the generality and utility of the object-based IOR effect. Chapter 3 demonstrated that presenting an (apparent) object at the cuetarget location is sufficient to trigger the object-based IOR effect. The observation that inhibition can spread across the surface of an object (Chapter 4) confirmed that pure object-based IOR is observed in static displays. Together these chapters provided a complete dissociation of the two independent IOR effects and suggests that they operate additively in the typical IOR procedure. Chapter 5 demonstrated that the separate inhibitory mechanisms have characteristic boundary conditions. Orienting attention within-objects abolishes the location-based IOR effect, but does not effect the object-based effect. In sharp contrast, increasing object salience modulates the object-based effect, but has no effect on location-based inhibition. Finally, there was no evidence of a retinotectal pathway involvement in the location-based IOR effect under monocular conditions. Rather, both effects appear to be generated by cortical regions, with an exclusively left visual field bias for the object-based IOR effect. It was concluded that object-based IOR effects generalise to static procedures, which seriously questions the interpretation that IOR effects observed in static displays are mediated purely by a spatial frame of reference. This conclusion may generalise to all static precueing procedures. The boundary conditions of the object-based IOR effect are consistent with a mechanism that serves to guide efficient visual processing.

No description available.

No description available.

Previous works suggest that North Americans perceive visual information more analytically while East Asians perceive visual information more holistically. However, salient objects are also known to naturally attract human attention. Current studies examined to what extent culture influences visual attention. Study 1 demonstrated that highly salient objects attract passive viewers attention similarly across North American and East Asian cultures. In study 2, however, we revealed that such strong tendency for humans can be influenced by culture when people actively engaged in the observation. When participants were asked to report their observation, Canadian participants predominantly reported information regarding focal objects whereas Japanese participants also reported much information regarding contextual features. Consistently, culturally divergent patterns of eye movements were observed. The current study thus indicates that the active involvement in observation is especially important to understand the influence of culture on visual attention.

In everyday life, we are constantly surrounded by a huge amount of information.Since our attentional resources are limited, we need to select just the stimuli that we want to process. Despite our voluntary attempt to select a precise information, it often occurs that a salient stimulus or event automatically captures our attention, regardless its irrelevance. The fact that we are immediately and unintentionally attracted by sudden visual onsets provides a clear advantage for our survival. However, in spite of that, the possibility to counteract visual distraction is fundamental for an efficient interaction with the environment, particularly when a salient but irrelevant stimulation repeatedly affects our visual system. And then, how can we resist from being continuously distracted by irrelevant repetitive onsets? The current work is aimed to explore the mechanisms that we use to filter irrelevant information, with a focus on habituation, an ancestral form of learning that has recently been associated to the decrement of attentional capture observed in several studies. This experience-dependent learning process is defined as a behavioral response decrement that results from repeated stimulation and that does not involve sensory or motor fatigue. I will first provide the reader with a general introduction (Chapter 1) concerning the visual attention field, with a particular emphasis on attentional capture and the filtering of irrelevant information. I will then (Chapter 2) try to disentangle the two main accounts concerning the nature of the distractor filtering, the first claiming that filtering is accomplished to shield target processing from interference (top-down inhibitory control hypothesis), and the second stating that the passive exposure to a repeating visual onset is sufficient to trigger learning-dependent mechanisms to filter the unwanted stimulation (habituation hypothesis). After providing strong evidence in favor of the latter account, I will then examine (Chapter 3) to what extent the filtering of irrelevant information that we achieve through the mechanisms underlying habituation is affected by contextual cues, showing that this kind of filtering is context-dependent. Finally (Chapter 4), motivated by the existence of a strong functional and anatomical link between attention and the oculomotor system, I will explore whether habituation affects also the oculomotor capture triggered by an onset distractor, showing that the execution of reflexive saccades is subject to habituation, while the programming component is not. Taken together, the results of the present work give a strong contribution to the attentional capture field in showing that both attentional and oculomotor capture are subject to habituation, that this form of learning is context-specific and that it occurs also when we are passively exposed to a visual irrelevant stimulus.

Thesis advisor: Sean MacEvoy / Humans can pay attention both to particular locations in space (“space-based attention”) and to specific objects (“object-based attention”). The goal of this study was to understand the role of object familiarity and complexity in the control of object-based attention. We used a well-known manifestation of object-based attention known as same-object advantage (SOA) to test this. In SOA, participants are faster at detecting a target event that takes place in a cued object than one that takes place in an uncued object, even when the distance between cue and target is kept fixed. To control shape familiarity, objects in the current study were randomly-generated irregular polygons known as Attneave shapes. Experiment 1 showed that SOA exists for these irregular shapes, even when participants are unfamiliar with them. In Experiment 2, participants first underwent training designed to familiarize them with a subset of the Attneave shapes used in Experiment 1. Again there was a significant SOA. If object-based attention is dependent upon object familiarity, we hypothesized that SOA, measured in terms of reaction time, should be greater in Experiment 2 than Experiment 1. Although there was a numerical increase in the reaction time signature of SOA in Experiment 2, this effect was not significant. While this does not strictly support our hypothesis, several aspects of this study suggest that object familiarity does play some role in mediating object-based attention. / Thesis (BS) — Boston College, 2013. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Psychology Honors Program. / Discipline: Psychology.