知覺組織強度可影響視覺搜尋中的共線遮蔽效應

Perceptual Grouping Strength can Modulate the Size of the Collinear Masking Effect in a Visual Search

顯眼的目標物通常能促進我們視覺搜尋上的效率。然而，Jingling等人（2013）卻發現，若顯眼的結構是由共線組織組成的，反而會阻礙視覺搜尋，稱為共線遮蔽效應。在該實驗中，此共線組織是由多個線段以頭尾相接方式排列成為一直行。因此，一個可能性是此共線組織的知覺組織強度影響了共線遮蔽效應的大小。本研究目的為探討共線遮蔽效應的強度是否會受到知覺組織的強度而變化。本研究嘗試減弱整個搜尋畫面知覺組織的強度，若共線遮蔽效果和知覺組織強度有關，則改變整個畫面的知覺組織強度應該也會改變共線遮蔽效果的大小。實驗一增加整個畫面的線段尺度（指線段與線段間隔的相對比例），實驗二則增加線段之間的間隔來減弱整體搜尋畫面的知覺組織強度。實驗三排除目標線段方位這個混淆因素。結果顯示，共線遮蔽效應的強度確實會隨著整體畫面知覺組織的減弱而降低，並且與目標物重疊於垂直或水平線段方位無關。我們推測整體知覺組織強度降低時，共線組織的強度也降低，因此降低了共線遮蔽效應的大小。因此推測共線性的知覺組織是引發共線遮蔽效應的重要條件。

Visual search efficiency can usually be promoted if the target is salient. However, Jingling & Tseng (2013) found that if the salient structure was composed of collinear bars, search would be more difficult — a phenomenon called the collinear masking effect. In their experiment, the collinear structure was composed of bars in a head-to-tail alignment. Thus, it is possible that perceptual grouping of the collinear distractor may play a role in the collinear masking effect. The current study aimed to reduce the strength of the perceptual grouping of the whole search display and to test whether the size of collinear masking effect also reduced. In Experiment 1, the scale of the bars (the size ratios of bars and spacing) was increased, and in Experiment 2, the spacing between bars was increased to reduce the grouping strength of the whole display. In Experiment 3, possible confounding of bar orientation of the target was removed. Our data showed that the strength of the collinear masking effect was indeed reduced because of the weakening of the perceptual grouping of the search display. Simply changing the orientation of the bar where target was on did not affect responses. We infer that the reduction of perceptual grouping strength of the whole display also reduced the grouping strength of collinear distractor, and hence the size of the effect. Therefore, collinearity grouping strength might be an important factor for the emergence of the collinear masking effect.