Blumenthal Emily J, Bosworth Rain G, Dobkins Karen R
Department of Psychology, University of California, San Diego, CA, USA.
J Vis. 2013 Nov 6;13(13):8. doi: 10.1167/13.13.8.
Although global motion processing is thought to emerge early in infancy, there is debate regarding the age at which it matures to an adult-like level. In the current study, we address the possibility that the apparent age-related improvement in global motion processing might be secondary to age-related increases in the sensitivity of mechanisms (i.e., local motion detectors) that provide input to global motion mechanisms. To address this, we measured global motion processing by obtaining motion coherence thresholds using stimuli that were equally detectable in terms of contrast across all individuals and ages (3-, 4-, 5-, 6-, and 7-month-olds and adults). For infants, we employed a directional eye movement (DEM) technique. For adults, we employed both DEM and a self-report method. First, contrast sensitivity was obtained for a local task, using a stochastic motion display in which all the dots moved coherently. Contrast sensitivity increased significantly between 3 and 7 months, and between infancy and adulthood. Each subject was then tested on the global motion task with the contrast of the dots set to 2.5 × each individual's contrast threshold. Coherence thresholds were obtained by varying the percentage of coherently moving "signal" versus "noise" dots in the stochastic motion display. Results revealed remarkably stable global motion sensitivity between 3 and 7 months of age, as well as between infancy and adulthood. These results suggest that the mechanisms underlying global motion processing develop to an adult-like state very quickly.
尽管人们认为全局运动处理在婴儿期早期就已出现，但对于其成熟到类似成人水平的年龄仍存在争议。在当前的研究中，我们探讨了一种可能性，即全局运动处理中明显的与年龄相关的改善可能继发于为全局运动机制提供输入的机制（即局部运动探测器）的敏感性与年龄相关的增加。为了解决这个问题，我们通过使用在所有个体和年龄（3个月、4个月、5个月、6个月、7个月大的婴儿以及成年人）中对比度均相同且易于察觉的刺激来获取运动连贯性阈值，以此测量全局运动处理能力。对于婴儿，我们采用了定向眼动（DEM）技术。对于成年人，我们同时采用了DEM和自我报告方法。首先，使用所有点都同向移动的随机运动显示来获取局部任务的对比度敏感度。3至7个月之间以及婴儿期与成年期之间，对比度敏感度显著增加。然后，将点的对比度设置为每个个体对比度阈值的2.5倍，对每个受试者进行全局运动任务测试。通过改变随机运动显示中同向移动的“信号”点与“噪声”点的百分比来获取连贯性阈值。结果显示，3至7个月大的婴儿以及婴儿期与成年期之间的全局运动敏感度非常稳定。这些结果表明，全局运动处理的潜在机制很快就发展到了类似成人的状态。
