Tseng C H, McNeil M R, Milenkovic P
National Chung-Cheng University, Chia-Yi, Taiwan, ROC.
Brain Lang. 1993 Aug;45(2):276-96. doi: 10.1006/brln.1993.1046.
Nine aphasic and 18 normal adults participated in a dual task with components of phoneme monitoring and semantic judgment. Subjects listened to lists of recorded spoken words and were required to detect semantic and phonetic targets. Two within-subject variables were manipulated: the probability of target occurrence for each dual-task component (.2, .5, and .8) and the explicitness of instruction (explicit vs. implicit). Only in the explicit condition were subjects told about the probability structure and given the attention allocation strategy congruent with that structure. Reaction times were recorded on-line for analysis by an IBM-AT. The results showed that normal subjects' overall latencies in detecting phonetic targets decreased as the target occurrence probability increased in both implicit and explicit instruction conditions. The detection latencies for semantic targets showed a similar probability effect but only in the explicit condition. By contrast, the aphasic subjects did not show the probability effect in any condition, although they performed above the chance level on both semantic and phonetic tasks. The presence of the probability effects for the normal subjects indicated that an efficient attention allocation mechanism was operating so as to optimize the performance level. On the other hand, the absence of probability effects for the aphasic subjects suggests that their attention control system might be inefficient so that task-demand cues (probability and attention allocation instruction) were not utilized properly.
9名失语症患者和18名正常成年人参与了一项包含音素监测和语义判断成分的双重任务。受试者听录制好的单词列表，并被要求检测语义和语音目标。操纵了两个受试者内变量：每个双重任务成分的目标出现概率（0.2、0.5和0.8）以及指令的明确性（明确与隐含）。只有在明确条件下，才会告知受试者概率结构，并给予与该结构一致的注意力分配策略。反应时间通过IBM-AT在线记录以便分析。结果表明，在隐含和明确指令条件下，正常受试者检测语音目标的总体潜伏期随着目标出现概率的增加而缩短。语义目标的检测潜伏期显示出类似的概率效应，但仅在明确条件下。相比之下，失语症患者在任何条件下都未表现出概率效应，尽管他们在语义和语音任务上的表现均高于随机水平。正常受试者存在概率效应表明一种有效的注意力分配机制在起作用，以优化表现水平。另一方面，失语症患者不存在概率效应表明他们的注意力控制系统可能效率低下，以至于任务需求线索（概率和注意力分配指令）未得到恰当利用。
