Central Attention To Capture The Impact Load On Spatial Attention

Traditional researches as to how bottom-up and top-down factors affect attentional capture have mainly focused on the nature and demands of the selective attention task itself. Recently, increasing experiments exploring the effect of attentional load on selective attention have been exploited to clarify the control mechanism of selective attention. Researches reveal that distractor processing depends critically on the level and type of load involved in the processing of goal-relevant information. Whereas high perceptual load can eliminate distractor processing, high load on'frontal' cognitive control processes increases distractor processing. As a capacity-limited central attention mechanisms, attentional blink paradigm can also be adopted to manipulate attentional load. Behavioral and electrophysiological studies show that a set of mechanisms subserving the voluntary allocation of attention in the spatial domain suffer significant interference from concurrent cognitive operations required to encode information into visual short-term memory. However, studies as to the involuntary deployment of visual-spatial attention, attentional capture, during attentional blink are seldom, and the results are inconsistent. Especially, in these paradigms, T1 was presented at fixation whereas distractors was presented in the periphery. Therefore, one possible interpretation of results of previous experiments was that spatial attention could not disengage from the position in which T1 was encoded during the consolidation of T1 in visual short-term memory.To rule out the influence of spatial attention focus, I used a variant of the original attentional blink paradigm that was designed to encourage subjects to make their spatial attention be in a wide, distributed state. I used four laterally displayed and synchronized RSVP streams of stimuli, in which T1 was composed of four simultaneous red letters, one in each RSVP stream. T2 was a color singleton or a specific color letter preceded by a distractor appeared either at the same location or different location as the subsequent target. To reflect actual shifts of spatial attention, reaction time was used to measure location congruence effect instead of accuracy which is commonly used in original attentional blink paradigm. The subjects were instructed to respond to the T2 first, as quickly as possible, and then to to detect the presence or absence of the T1 presented on half of the trails at their leisure. It is believed that attending to T1 when it appeard engage attentional resource, hence the presence of T1 served as high load condition.In experiment 1, an uncertain color singleton served as target, and the color of the abrupt onset serving as distracted cue was also uncertain. It is believed that participants use Singleton Detection Mode in this condition. Result demonstrares that the capacity of distracted cue to capture attention is significantly enhanced in high load condition compared to low load condition. In experiment 2, participants had to adopt Feature Search Mode to search the target with a specific color(red). Same as designs used in the majority of similar studies, the color of target and salient distracted cue fixed throughout the experiment. The result replicates that of experiment 2 only when SOA between T1 and distracted cue is 100ms. Experiment 3 examined effect of load on pure contingent capture elicited by a target-colored nonsingleton cue among heterogeneously colored cues in Feature Search Mode. Contrary to former results, magnitude of attentional capture was significantly attenuated in high load condition.Integrated results of three experiments in the current research and conclusions in other relevant studies, several conclusions were got as follows:1.Attending to T1 in current experiments load central attention mechanisms which is a postperceptual stage of processing, whereas manipulations of attentional resource in previous studies in which T1 is presented at fixation interrupt processing of distractors at perceptual level.2.The central attention mechanisms involved in the current research is related to executive control processes.3.Loading central attention mechanisms may affect attentional capture by interrupting the control of attentional set in target selection.4.Increasing central attentional load result in loss of control at earlier spatial selection stage rather than other later stage such as consolidation into working memory and response selection.