The Preview Effect In Pattern Recognition

The Preview Search paradigm is an important method of priority selection mechanism in the visual search, since it was created by Watson and Humphreys, in 1997. It meaned that, the distraction presented earlier, will be effectively filtered, so that the search performance is improved, a phenomenon known as the "preview effect." Previous studies,mainly, regarded letters or numbers that we are so familiar,as experimental materials, while familiarity is an important factors affecting the effience of visual search. In this study, we use graphics as the experimental materials, with standard preview search paradigm, in order to examine the Preview Effect in Pattern Recognition, as well as, to further explore its cognitive mechanism. The Study is divided into three parts including four experiments:The first part is about regular graphics' recognition, including two experiments, with the color's consistency of the new and old objects as Control Variables. The results showed that: (1) When the color of new and old objects are different, Complete Preview Effect appeared. the speed of preview search is significantly faster than the that of full-set baseline, close to half-set baseline search; (2) When the color of new and old objects is the same, only partial Preview Effect appeared. Well, although the preview search effience is significantly higher than the full-set baseline, but also slower than the half-set baseline, ranging between the two. Therefore, the color plays a key role in improving the search performance, and if solely relying on "location" clues, it can not obtain the best preview effects, Preview Effect is based on both of the old object's'location' and 'color'.The second part of the research is about curvilinar graphics'recognition. In order to further explore the importance of color cues, in experiment 3, the color of old and new objects is the same. It found that:the speed of Preview Search was faster than that of full-set baseline, and close to half-set baseline search; and both the number of old and new objects influenced search effience significantly, but that of the new was more significant. So there is just partial preview effect in curve graphics'recognition. Maybe, due to loss of color cues, the individual can not effectively filter the old objects.The third part is about irregular graphics'recognition. What is different to Experiment 3, is that a few of the old and new objects are the same. all stimulus are different in shape,but the same in color. Surprisely, no subjects found the overlap between the old and new objects. This experimental results are generally indentical to the curve graphic, just due to the complexity of random graphics, the overall rise in reaction time can be seen. It showed that, with the familiarity of objects lowed, the Preview Effect became weak.This study developed and validate the theoretical explanations about preview effect, explored the factors that may influence the effect of preview,as well as their weight, and deepened the understanding of human visual search. It not only confirmed the universality of the preview effect,but also provided practical significance for web design, search operations and so forth.