Attributes Of Vigilant Attention Of Detection For Visual Stimulus

Moray (1969) thought that attention contained six features, which were concentricity, vigilant, selectivity, search, awareness and set. Vigilance (sustained attention), is a special form of attention. Although different researchers have different expressions for the definition of vigilance, yet, they have some commons in defining alertness. By summarizing up these commons, this research defined vigilance as the special attention of the persistent detection and facility readiness that individuals maintained to the stimuli which, not appeared but possible, have important adaptive significance for them. Therefore, in this research, vigilance is called vigilant attention. Traditional vigilant task is to let tested long time to detect the occurrence of signal with lower probability, during this process the vigilant performance might decrease as time goes by (Botella, Contreras, Shih,&Rubio,2001; Eysenck,1982; Grier et al.,2003; N. Mackworth,1948). For such kind of recessing phenomenon, researchers explained it from different angles. Thus it could be seen that the existing studies of vigilance have done much for the recessing phenomenon, but vigilance'spatial distribution and its attributes and mechanism still need to be carried on a deeper research.In the field of attention, though researches on inhibition of return (IOR) and the spatial scale of visual attention involved attributes and mechanism of time and space for attention processing, yet these researches haven't discussed from the aspect of vigilance. Therefore, this research studied spatial distribution and its attribute of changing as time goes by of system's vigilant attention on the detection of visual stimulus, respectively. from the aspects of behavior and electrophysiology. Besides, this research employed experimental paradigm of "preparing prompt-early warning prompt-target stimulus detection" by simulating the "on your mark-get ready-go" model of sports competition.Through controlling time interval (vigilant time) between early warning prompt and the appearance of target stimulus, experiment1explores stable feature of vigilant attention, i.e. investigates vigilant attention's variation tendency in time dimensionality. This experiment was the design of two-factor within-subject repeated measurement. Factor one was the probability of the appearance of two kinds of stimuli (two levels, high probability2/3and low probability1/3), factor two was the length of vigilant time, seven levels, they were200ms,400ms,600ms,800ms,1000ms,1200ms and1400ms. Vigilant situation was established through uncertainty of forthcoming target stimulus in time interval that after early warning prompt. Results of this research showed that while vigilant time was within800-1000ms, detecting speed for the target stimulus was the fastest, which seemingly indicated that this vigilance was the optimal period for the detection of visual target stimulus. It suggested that vigilance has the characteristics of selectivity, stability, and volatility.Based on experiment1, experiment2moved a further step to study whether vigilant attention was influenced by the position change of visual target stimulus' appearance in space. This experiment created vigilant situation through uncertainty of the forthcoming stimulus in time interval after early warning prompt as well as its spatial position. Its design was the two-factor within-subject design of4(lengths of vigilant time were:400ms,700ms,1000ms and1300ms)×4(spatial position target stimulus appeared:central origin, visual angles of diameter were2°,5°nd8°). The dependent variable was the same as experiment1. Selection of vigilant length was depended on the results of experiment1. At the aspect of spatial variable, it mainly consulted partition of the studies of the spatial scale of visual attention. This experiment, expect getting the same results with experiment1, it also found that with distance enlargement (unrelated to directions of up and down as well as right and left) of the position visual target stimulus appeared from central origin (the place where prompt information emerged), individual's reaction speed to target stimulus detection also declined step by step and the grade decreasing was presented in0°(central origin)-2°/°-8°diameter angles. It suggested that vigilance has the characteristics of concentration.It was needed to be pointed out that the above behavior research discovered only initially revealed visual stimulus detection's feature of vigilant attention in time index. Besides time index, ERP (Event-related Potential) was also an effective study method for attention. Different components of ERP represented abundant brain cognitive processes; by taking advantage of these messages about brain processes the special mechanism of visual stimulus detection's vigilant attention could be deepened. Therefore, based on experiment1and experiment2, this research conducted two ERP experiments and got some meaningful results about electrophysiological researches. Specifically speaking, by employing ERP technology, experiment3studied influence of different vigilant time (chose400ms,700ms and1,000ms) on the detection of visual target stimulus. The results were consistent with experiment1in time index, and components of ERP didn't show distinctive differences after the appearance of target stimulus in three different early warning times. However, through comparing dynamic time variations in the brain, within1,000ms, after the appearance of preparing prompt and early warning prompt, it found out that early warning prompt, in early stage (230-280ms) and later stage (500-900ms), induced a more positive P2and a more negative LNC (late negative component) respectively, which might indicate early warning of the tested for the forthcoming of target stimulus and its preparing status for concentrative attention to carry out key actions. Combining researching results of experiment2and3, experiment4adopted ERP only to discover ERP effect of target stimulus'spatial variations in emerging position (three conditions for spatial position target stimulus emerged:diameter angles were3.2°,6.4°nd9.6°) on target detection. In reaction time it also found out that if vigilant attention's resources became closer to center, then it got more attention resources, if became further the allocated resources were fewer, which was represented in the model of spatial gradient. As for ERP, wave patterns induced, after the emergence of target stimulus produced, respectively, different degrees of isolation in N1and LPC, under three different conditions, which proved the model of reaction time.Through conducting system analysis for behaviors and ERP research, this research thought that diameter angle within the range of10°, spatial feature of visual stimulus detection's vigilant attention was revealed in primary and also been proved. However, what was the feature of the alert attention of visual stimulus detection in a larger range (for example, above10°)? Secondly, the former research set preparing time (time interval from preparing prompt to early warning prompt) as the constant1,000ms all the time. Furthermore, whether the stimulus of early warning prompt would disappear after appearing, the former experiment didn't discuss it specially.This research carried out three more refined behavior experiments with this problem and factors. Firstly, experiment5investigated preparing time and early warning time's influence on vigilant attention of visual stimulus detection. This experiment was5(preparing time:1,000ms,1,500ms,2,000ms,2,500ms and3,000ms)×7(vigilant time:100ms,400ms,1,000ms,1,300ms,1.600ms and1,900ms) two-factor within-subject design. The dependent variable was the same as experiment one. The experimental result indicated that1,000ms was still the best vigilant time for the detection of target stimulus. What's more, within2,500-3,000ms preparing time, it discovered that all the vigilant times possessed the best detections for target stimulus. Experiment6, based on experiment5, chose one of optimal preparing time (2,500ms) as the constant one. This experiment mainly studied the influence of vigilant time (6levels:300ms,600ms,900ms,1.200ms,1,500ms and1,800ms) as well as the influence of whether early warning prompt would disappear after emerging on the detection of target stimulus. The independent variable was the same as experiment1. Experimental result also received the optimal alertness time (1,200ms) rather close to those of former researches. In spite of it, this research also found out that early warning prompt didn't disappear after emerging, while reaction speed of individual detection for target stimulus was obviously faster than disappearance, it might suggest the disappearance of early warning prompt would make individuals keep their high level of waking up status for the position target stimulus appeared (original point of center where target stimulus always appears and has appeared). Therefore, while moving forward a single step to investigate vigilant time's feature of detection for visual stimulus while diameter angle was larger than10°, experiment7supposed the early warning prompt would disappear after emerging to avoid individuals concentrating attention resources passively on the central position. This experiment was the two-factor tested inner design of3(vigilant time:300ms,900ms and1,500ms)×15(spatial position target stimulus appeared: original point of center and fourteen different positions whose diameter angles were larger than10°). The experimental result showed that while diameter angle was larger than10°, the optimal vigilant time for the detection of visual stimulus was about900-1,500ms, which matched to the former experimental results. The most important was that this experiment also indicated that while diameter angle was larger than10°, the alertness process was influenced not only by the size of diameter angle in spatial distribution, but also by the directions of view. Compared with the condition while diameter angle was smaller than10°, vigilant attention, at the moment, didn't comply with the spatial gradient model in spatial feature, but presented in the irregular distribution. Specifically speaking, under the same diameter angle, individual's detection speed for target stimulus at right and left was faster than that of stimulus located up and down, and the detection reaction for the up target stimulus was quicker than that of down stimulus.All in all, this research discovered that, under the vigilance's experimental paradigm of "preparing prompt-early warning prompt-target stimulus detection",(1)2,500-3,000ms might be the best preparing prompt time, while around1.000ms it might be the best vigilant time, it suggested that vigilance has the characteristics of selectivity, stability, and volatility.(2) While stimulus'diameter angle was within10≡°, the time and spatial distributions of individual's alertness processing fitted spatial gradient model, at this moment, resources of vigilant attention was presented in the state of decreasing progressively from central origin to outsides, it suggested that vigilance has the characteristics of concentration.(3) When diameter angle was larger than10°, vigilance' distribution in time and space was affected by stimulus'located attention range as well as its visual directions, it suggested that vigilance has position advantage effect. The above results showed that as a special attention form, vigilant attention had its own processing mechanism.