| Search asymmetry is a well-known phenomenon in which searching for stimulus A among a background of distractors B is more efficient than searching for B among A. Asymmetry paradigm has been used to understand the attentional mechanism in the human vision system. Feature Integration Theory indicates that it is easier to detect the presence of a basic feature, which happens in the preattentive stage, than it is to locate its absence. Experiments driven by the familiarity-based perspective suggest that the familiarity of the distractors determines search efficiency so that unfamiliar distractors slow down the search speed. According to the prototype-deviation hypothesis the deviating stimuli elicits more activity than do the standard ones, thus searching for a high-activity target among low-activity distractors is faster than reverse.The aspects of information theory introduce "scannig-predicting" procedure to interpret the way stimulus be proccessed by visual system, which providing techniques for quantifying situations which have hitherto been difficult or impossible to quantify. In this paper I shall adopt these informational aspects of visual perception to reconsider the phenomenon of visual search asymmetry.In Experiment 1, Chinese character and its trasform were used as target and distractors to demmonstrate that it is the facotor of amount of information rather than familiarity or prototype-deviation element determines search efficiency. In Experiment 2 stimulus with substitutive features and different amount of information are used as target and distractors to prove it is the amount of information not the basic features affects search efficiency. Experiment 3 gave a primary discussion on the influence of uncertainty on visual search performance.The results suggest that (1) it is more efficient to search for a target with more information than with small information; (2) some aspects of information theory can be used to interpret the phenomenon of visual search asymetry.
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