以往的研究利用不同的派典、操弄探討聲音刺激對於視覺運動方向偵測或辨別能力上的影響，其效果與成因各有差異。本研究採用等雜訊實驗派典 (equivalent noise (E.N.) paradigm) 探討聲音 (無聲、無方向性、與視覺刺激同向及與視覺刺激異向) 是否會改變視覺整體運動方向的辨別能力，並利用等雜訊模型 (E.N. model) 分析聲音影響了整合歷程中的哪一個階段：對於偵測局部運動訊號移動方向的不確定性 (內在雜訊，internal noise) 、改變使用多少局部運動訊號進行整合的能力 (抽樣效率，sampling efficiency) ，或是兩者皆有。筆者所採用的視覺刺激為一百個移動方向來自於同一常態分配的點，其平均數為移動方向，其標準差被視為外在雜訊 (external noise) ，測量受試者在不同的外在雜訊下，視覺刺激的平均移動方向需偏移九十度(垂直向上移動)幾度，受試者才能成功辨別整體的移動方向。實驗一，利用強迫選擇法 (two-alternative forced choise) ，受試者判斷視覺刺激的平均運動方向為左或右。其結果為隨著外在雜訊越高，對於運動方向辨別的閾值越高。不同聲音刺激下也沒有差異。在視覺方向判斷作業中，受試者會受聲音刺激造成反應誤差 (response bias) ，內在雜訊與抽樣效率不會受到影響。 實驗二，利用兩區間強迫選擇法 (two-interval forced choise) ，目標區間的平均移動方向為向右或向左，另一區間的平均移動方向為正上方，受試者選擇目標區間。其結果與實驗一相同，隨著外在雜訊越高，受試者的閾值越高，不同的聲音並沒有差異。內在雜訊與抽樣效率並不會受到聲音刺激的影響。實驗三，與實驗二相同皆利用兩區間強迫選擇法。與實驗二不同的在於目標區間的平均移動方向為向左。其結果與實驗一、二結果皆相同，都為隨著外在雜訊越高，受試者的閾值越高，在不同的聲音之下閾值並沒有差異。綜合本研究的三項實驗，在不同的作業之下結果皆維持一致，外在雜訊的多寡為影響受試者反應的主要因素，聲音刺激不會影響受試者的內在雜訊與抽樣效率。

The past studies in audiovisual motion interactions have shown different results. The aim of this study is to investigate how sound influences on visual global motion discrimination so as to define the role of auditory stimuli in visual motion integration processing. In this study, we applied equivalent noise (E.N.) paradigm and E.N. model to analyze how auditory stimuli influence the visual motion integration processing across two parameters: internal noise (precision in detecting local motion direction) and sampling efficiency (ability to pool the local motion across space). The visual stimuli consisted of 100 dots that moved in directions assigned from a normal distribution. We examined how many degrees of movement direction deviated from vertical-upward that observers could discriminate successfully under four sound conditions (absent, stationary, incongruent, and congruent sound), and examined the performance at different standard deviations (SDs, as the external noise in the paradigm). Two-alternative forced choice method were used in Experiment 1: observers responded to the mean direction of moving dots. The results showed that thresholds increased with increasing SD, but the rate of increase did not significantly differ between the conditions. That is, neither internal noise nor sampling efficiency was changed under different sound conditions. We used two-intervals forced choice method in Experiment 2 and 3 to investigate whether this phenomenon was stable in different task. In Experiment 2, the observers responded to the interval which consisted the mean direction that was right-upward or left-upward instead of vertical-upward. In Experiment 3, the observers also responded the target interval which the mean direction was left- upward. The results of these experiments also showed that thresholds increased with SD, but the rate of increase did not significantly differ between the conditions. It suggests that the sound does not change the local motion direction detectability or pooling ability.

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