Kuroda Tsuyoshi, Yoshioka Daiki, Ueda Tomoya, Miyazaki Makoto
Faculty of Informatics, Shizuoka University, Hamamatsu, Japan.
Yamaha Motor Co., Ltd, Fukuroi, Japan.
Front Hum Neurosci. 2018 Feb 2;12:31. doi: 10.3389/fnhum.2018.00031. eCollection 2018.
Discrimination of two neighboring empty durations that are marked by three successive sounds is improved when the presentation of the first (standard, S) duration is repeated before that of the second (comparison, C), as SSSSC. This improvement in sensitivity, called the multiple-look effect, has been explained by a statistical model regarding variability. This model assumes that the perceived duration of the standard is averaged across observations (within a trial within an individual). The increasing of the number of observations thus reduces the standard error of the mean perceived duration. Alternatively, the multiple-look effect is attributed to the listener's prediction based on regular rhythm. Listeners perceive regular rhythm during the repetition of the standard, predict the timing of subsequent sounds, and detect a sound that is displaced from the predicted timing. These models were tested in the present experiment in which the main factor was a temporal separation between the standard and the comparison; i.e., these durations were adjacent to each other as SSSSC or separated by a temporal blank as SSSS_C. The results differed between stimulus structures. First, the multiple-look effect was replicated in the SSSSC condition (yielding a higher performance than SC), but disappeared in SSSS_C (having no difference with S_C). Second, no multiple-look effect occurred in CSSSS (no difference with CS), and moreover, an impairment effect was observed in C_SSSS (a lower performance than C_S). Finally, discrimination was improved in SSSS_CCCC compared with SSSSCCCC, the effect being kept even when sounds were aligned at irregular intervals. These findings are not consistent with those expected from the statistical model because the temporal separation should have produced no effects if the number of standards had been a sole parameter determining the multiple-look effect. The prediction-based model can explain the first finding; inserting a blank between the standard and the comparison violates the listener's prediction based on regular rhythm, thus reducing the multiple-look effect. However, it did not expect the other findings and required revisions. Notably, the second finding indicates that the formation of regular rhythm can impair temporal discrimination. In other words, an multiple-look effect occurs.
当第一个（标准，S）时长在第二个（比较，C）时长呈现之前重复出现，即呈现为SSSSC时，对由三个连续声音标记的两个相邻空时长的辨别能力会得到提高。这种敏感性的提高，称为多注视效应，已由一个关于变异性的统计模型进行了解释。该模型假设标准时长的感知时长是在观察结果（在个体的一次试验内）上进行平均的。因此，观察次数的增加会降低平均感知时长的标准误差。或者，多注视效应归因于听众基于规律节奏的预测。听众在标准时长的重复过程中感知到规律节奏，预测后续声音的时间，并检测偏离预测时间的声音。在本实验中对这些模型进行了测试，其中主要因素是标准时长和比较时长之间的时间间隔；即这些时长彼此相邻，如SSSSC，或被一个时间空白隔开，如SSSS_C。刺激结构不同，结果也不同。首先，在SSSSC条件下重复了多注视效应（表现高于SC），但在SSSS_C中消失了（与S_C没有差异）。其次，在CSSSS中没有出现多注视效应（与CS没有差异），此外，在C_SSSS中观察到了损害效应（表现低于C_S）。最后，与SSSSCCCC相比，SSSS_CCCC中的辨别能力得到了提高，即使声音以不规则间隔对齐，这种效应仍然存在。这些发现与统计模型预期的结果不一致，因为如果标准时长的数量是决定多注视效应的唯一参数，那么时间间隔应该不会产生影响。基于预测的模型可以解释第一个发现；在标准时长和比较时长之间插入一个空白会违反听众基于规律节奏的预测，从而降低多注视效应。然而，它没有预期到其他发现，需要进行修正。值得注意的是，第二个发现表明规律节奏的形成会损害时间辨别能力。换句话说，出现了多注视效应。
