視覺搜尋中，具有知覺群聚特性或顯眼的物體通常會獲取注意力，若目標位於顯眼的干擾物上應有益搜尋。但以生物為例則可能採取相反的策略如偽裝，以不受注意的方式藏匿於環境。本實驗室先前的研究發現，當目標與顯眼的干擾物重疊時，梯形干擾物促進搜尋，但蛇形干擾物卻產生共線遮蔽效果抑制搜尋。因此本研究欲探討促進和遮蔽效果與干擾物的知覺組織（相似性和連續性）和顯著性的關聯。實驗一驗證先前研究，以梯形（非共線）和蛇形（共線）組織產生相反的搜尋效果。接著，實驗二去除干擾物內容的相似性（由直線改為曲線），以及操弄背景質地的相似性（均質和異質），有四種刺激：蛇形均質、蛇形異質、梯形均質、梯形異質。實驗三進一步以蛇形曲線干擾物在異質背景中，操弄干擾物旁側線段的方位（正交、平行與隨機），測試干擾物本身的顯眼程度以及對搜尋的影響。結果發現，蛇形干擾物是否同時具有相似性或顯著性不影響遮蔽效果，但是梯形干擾物若在異質背景就失去其促進效益。當蛇形干擾物旁側線段為正交情況時最顯眼，但是三種旁側情況皆有遮蔽效果且與顯眼程度無關。因此僅具顯著性的物體促進搜尋，若具有連續性則提供遮蔽條件。生物偽裝的擬態或許以此機制作為基準。
Salient or well-grouped stimuli usually capture attention. However, our previous studies showed a masking effect by a salient collinear distractor (i.e., snake) on a local target in visual search. Meanwhile, a salient non-collinear distractor (i.e., ladder) indeed facilitate search. The main difference between snake and ladder distractors was the grouping law good continuity. Nevertheless, the grouping law similarity and salient orientation contrast can also affect search performance. This study aimed to test whether continuity is enough to elicit the masking effect. Experiment 1 replicated the previous study in that snake distractor indeed impairs while ladder facilitates search. Experiment 2 made the distractor curved and reduced similarity in the background. Results showed that snake distractors impair search regardless of background homogeneity while ladder distractors facilitate search only when background bars were homogeneous. Experiment 3 manipulated the flankers of the snake distractor. Results showed that the orthogonal flankers make the distractor most salient; however, the effect size of the masking effect did not correlate to the degree of salience. Our results suggest that a distractor grouped with good continuity masks visual search, and the masking effect is irrelevant to the perceptual salience of the distractor. Meanwhile, a salient distractor can facilitate search. Thus the masking effect by a salient collinear distractor reported in our previous study must be caused by the grouping law of continuity.
