抽象圖形的短期視覺記憶：以局部再認作業與改變偵測作業來探討

Visual Short-Term Memory for Abstract Patterns: Explored with a Local Recognition Task and a Change-Detection Task

本研究採用新奇的抽象圖形（由紅／白色方格組成的5 × 5宮格），以兩種不同的作業典範來探討抽象圖形的短期視覺記憶的特性。實驗一以電腦化局部再認作業來檢測圖形之亂度、對稱性、以及探針所在的象限位置，是否會影響短期記憶的正確性。結果顯示高亂度圖形的再認錯誤率約為低亂度圖形的兩倍，反應時間較慢；對稱圖形的錯誤率顯著低於不對稱圖形，反應時間較短；而當探針在第四象限（右下角）時的錯誤率與反應時間皆高於其他象限。知覺複雜度與錯誤率的相關分析顯示：不對稱圖形之錯誤率與分散度呈現高度正相關、與緊緻度則呈現負相關，而對稱圖形的相關係數較低。實驗二採用改變偵測作業發現各變項的主要效果仍然存在，其中對稱效果擴大、亂度效果縮小，且不對稱圖形的緊緻度與分散度指標皆與錯誤率呈現無相關，對稱圖形的相關係數則無太大改變。這表示當參與者在進行局部再認作業時，局部區塊的複雜度影響較大；反之，當進行改變偵測作業時，參與者會對整體特性（如對稱性）有較敏銳的反應，而局部複雜度的影響反而較小。這意味的是，刺激圖形會隨著作業的不同與參與者的策略而被偏重於提取某種特性，也就代表我們在記憶抽象圖形的方式是極為彈性，且不被侷限在某種性質之中。

The present study investigated visual short-term memory for abstract patterns with two different paradigms: A local recognition task (Exp. 1) and a change-detection task (Exp. 2). Experiment 1 adopted a local recognition task to test whether pattern symmetry, element scatteredness, and probe location would affect the accuracy of visual recognition memory. The results on group accuracy and response time revealed significant and robust main effects for symmetry, element connectedness, and probe quadrant, showing that the memory was more accurate and faster when the pattern was symmetrical, had a higher connectedness, and was more error-prone for probes located in the low-right quadrant. In Experiment 2, we tested the same effects with a change-detection task that encourages subjects not only memorize local parts but also the whole pattern. The results also showed significant main effects for symmetry, element connectedness, and the changing quadrant. As compared to Experiment 1, the symmetry advantage in the change-detection task was augmented while the effect of element connectedness was decreased. Taken together, our study suggests that the representations in visual short-term memory are robustly affected by global (symmetry) and local complexity (element connectedness), but the weights can be flexibly adjusted according to the task demand.