The computation of relative numerosity, size and density.
The computation of relative numerosity, size and density.
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DOI：
10.1016/j.visres.2014.12.022
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发表时间：
2016-07
期刊：
影响因子：
1.8
通讯作者：
Morgan MJ
中科院分区：
文献类型：
--
作者：
Raphael S;Morgan MJ
观察者可以准确地辨别不规则形状阵列中的点数。准确性低于以前报道的规则形状的阵列。观察者可以区分点密度的变化与阵列尺寸的变化。结果是一致的计算数量的大小和密度。为了研究相对数量感知的机制，我们使用两个时间间隔的强迫选择（时间2AFC）来测量点纹理之间的面积，密度和数量差异的阈值，以及2 × 2 FC任务来测量观察者区分面积变化和密度变化的能力。为了防止使用一维尺寸信号，我们使用了纹理，其中点分散在不规则的多边形区域内。数量阈值相似的面积和密度变化的条件下，符合一个单一的数量机制。当数量保持不变时，面积和密度歧视的数量增加，与数量阈值低于大小和密度一致。此外，当轮廓中不存在点时，多边形轮廓的面积阈值增加。然而，一个单一的数量机制不能解释所有的数据，因为我们发现，观察员在随机交错的大小变化和密度变化的条件下，也能够区分大小和密度的变化与预测的精度从独立的噪声大小和密度通道，具有类似的噪声，在推定的数量通道。前面提到的圆形的复杂性是，密集的纹理往往与较大的纹理混淆，反之亦然。这可以解释为什么在常数情况下，当密度和大小变化相反时，阈值会上升。这些发现并不排除一个独立的数量机制，但他们同样是兼容的灵活计算的数量从大小和密度线索。
Observers could accurately discriminate dot number in irregularly shaped arrays. Accuracy was less than that previously reported for regular shaped arrays. Observers could discriminate changes of dot density from changes in array size. Results are consistent with a computation of number from size and density. To investigate the mechanisms for the perception of relative numerosity, we used two-interval forced-choice (temporal 2AFC) to measure thresholds for area, density and numerosity differences between dot textures, and a 2 × 2 FC task to measure the ability of observers to distinguish changes in area from changes in density. To prevent the use of a one-dimensional size signal we used textures in which dots were scattered within irregular polygonal areas. Numerosity thresholds were similar in the area and density-varying conditions, consistent with a single numerosity mechanism. Thresholds for area and density discriminations were raised when number was held constant, consistent with numerosity thresholds being lower than those for size and density. Also, area thresholds for polygonal outlines were increased when no dots were present in the outline. However, a single numerosity mechanism cannot account for all the data, because we find that observers in randomly-interleaved size-varying and density-varying conditions are also able to discriminate between changes in size and density with a precision predicted from independently-noisy size and density channels that have similar noise to that in the putative numerosity channel. A complication, previously noted with circular shapes, is that denser textures tend to be confused with larger textures, and vice versa. This could explain why thresholds rise when density and size changes are in opposition, in the constant-number case. These findings taken together do not rule out an independent numerosity mechanism, but they are equally compatible with a flexible computation of numerosity from size and density cues.