| 摘要: | 過去研究中顯示注意力暫失(attentional blink)是個後知覺障礙 (postperceptual deficit) 所造成的，大部分研究主要著重在T2如何受到在還處理中的T1干擾，但是最近有研究顯示出在極短時間間距時，T2表現會顯著比T1來的好，這樣結果似乎挑戰過去對於注意力暫失的解釋。Potter等人(2002)依據在短時間間距的結果提出two-stage competition model來解釋，這樣two-stage competition model認為T1和T2在不同時間點的表現結果反映出T1和T2在不同時間點的競爭優勢。然而在Potter et al (2005)利用語意相關性來探討競爭效果時，發現這樣競爭造成可能是全有全無的結果，也就是只有勝者會拿走所有資源。在目前實驗中試圖利用逐漸變化指標，數字距離效果，來看是否這樣T1和T2資源競爭是否會隨著T1和T2之間數字距離操弄造成逐漸改變的變化。 行為實驗中，結合視覺序列呈現作業和數字比較作業，要求受試者辨識T1和判斷T2比T1數值大或者是小。結果顯示，注意力暫失的確受到數字距離操弄反映出顯著數字距離效果在T2正確率上；另一部份，當T2緊隨T1之後馬上呈現時，T2正確率的確比T1顯著好，這和過去Potter及同事的研究結果吻合，而且更進一步發現T1錯誤型態主要是受到T1和T2之間數字距離影響，造成T1置換成T2的比率會隨數字距離而改變。 在腦波實驗中，主要探討注意力暫失和P300之間的關係；並進一步研究數字距離效果是否會反映在腦波上。目前的結果顯示，在注意力暫失情境下，只有正確回答的T2才會引發P300效果，而且在正確回答T2的情況下，腦波(N1~ P2P)也會隨著數字距離的改變而顯現出不同的強度。 這些結果更進一步支持注意力暫失是後知覺造成問題，而且即使受試者沒有辦法覺察到刺激存在，行為表現仍受到目標刺激之間關係的操弄，顯示出數字距離效果。In the conventional attention blink paradigm, researchers have been focusing on the deteriorated performance of the second target (T2) caused by the preceded identification of the first target (T1). Many behavioral and neuroimaging studies have revealed that the main cause of the attentional blink phenomenon is a post-perceptual deficit, namely, working memory updating limitation. Recently, Potter and colleagues (2002; 2005) have demonstrated that T1 can be outperformed by T2 when they are presented temporally close to each other (i.e.: the SOA between T1 and T2 is within 53 ms). Their findings have challenged a prevailed assumption in the AB literature, that is, the T1 always dominates in the access to the central processing system. Irrespective of the earlier entry of T1 to the system at short lags, subjects’ performance is better on T2. Potter et al (2002) has proposed that T1 and T2 intensely compete for attentional resource during the early stage of processing and T2 could win over the competition if it is presented right after the T1 without a distracter between them. Davenport and Potter (2005) have indicated that this competition is reliant on the relationship of T1 and T2. They used semantic related words as stimuli and showed that only T2 can prime T1 but not the reverse. Their demonstration successfully illustrates some features of competition. The competition two-stage model open up the possibility that the competition between T1 and T2 may be the main course of the AB and the lag1 sparing effect. Nonetheless, the semantic stimuli can only result in an all-or-none behavioral index. By using a more quantitatively measures, namely, the numerical distance effect, I attempt to clarify the characteristics of the competition in the attentional blink. With the manipulation of the number distance between T1 and T2, I aim to investigate whether the competition between T1 and T2 is a gradual competing process and the AB will be modulated by the number distance. In the behavioral experiment, I use a rapid serial visual presentation (RSVP) task to probe the fate of the number distance effect at lag 1 and in the attentional blink period. In the RSVP task, subjects were required to identify a double-digits number (served as T1) then compared whether the second double-digits number (served as T2) was larger or smaller than T1. The numerical distance between T1 and T2 were systematically manipulated in the task. The behavioral data indicated that the performance of T2 surpassed over that of T1 at lag1 and the reverse pattern of the result was observed in the longer lags (i.e. AB effect). In the longer lags condition, subjects’ performance was deteriorated with the decrement of the numerical distance. This pattern of results is consistent with the predication that the competition between T1 and T2 is a gradual effect and the numerical distance between T1 and T2 can modulate AB. However, in the lag 1 condition, the numerical distance effect was also found but the pattern of it is reverse from the one observed in the condition of the longer lags condition. Apart from the distance effect, the error pattern indicated that subjects were inclined to mistaken T2 as T1 when they made errors. These intrusion errors also intensify with the decreased distance between T1 and T2. It seems that the numerical information is processed in the lag 1 condition. In the ERPs experiment, I investigated the relationship between AB and P300 component (e.g.: Kranczioch et al., 2003) and probed whether the number distance effect can be reflected by ERPs waveforms (e.g.: Dehaene, 1996) The pattern of the result is consistent with the previous findings showing that the amplitude of P300 of correct T2 is significantly higher than incorrect T2 during the attentional blink period. Furthermore, the results also demonstrate that when T2 was correctly reported, the numerical distance information can also be reflected on ERPs component N1~ P2p during the attentional blink period. |
