Giaschi D, Regan D
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Optom Vis Sci. 1997 Sep;74(9):761-7. doi: 10.1097/00006324-199709000-00024.
Three-month-old infants can discriminate motion-defined (MD) form, but we do not know the age at which this ability reaches adult levels. Previous psychophysical evidence suggests that different neural mechanisms are involved in the processing of luminance-defined (LD) and MD spatial form in adults. This difference may be reflected in the development of LD versus MD form identification in children.
We measured speed threshold for identifying MD letters, letter-chart (i.e, Snellen) acuity for high-contrast LD letters and single-letter acuity for high- and low-contrast LD letters. Forty-seven children between 3 and 12 years of age and 20 adult subjects were tested.
Development to the adult level was observed as follows: low-contrast single-letter acuity before 3 years; high-contrast single-letter acuity by 5 to 6 years; the ability to identify MD letters by 7 to 8 years; letter-chart acuity by 9 to 10 years.
MD form identification continues to mature in preschool children. LD form identification also matures in this age group but with a different time course. MD letters are not equivalent to low-contrast letters developmentally. Our findings provide further support for the hypothesis that the spatial aspects of MD and LD form are processed separately to some extent.
三个月大的婴儿能够辨别基于运动定义（MD）的形状，但我们尚不清楚这种能力达到成人水平的年龄。先前的心理物理学证据表明，在成年人中，不同的神经机制参与了基于亮度定义（LD）和MD的空间形状的处理。这种差异可能反映在儿童对LD和MD形状识别的发展过程中。
我们测量了识别MD字母的速度阈值、高对比度LD字母的字母表（即斯内伦）视力以及高对比度和低对比度LD字母的单字母视力。对47名3至12岁的儿童和20名成年受试者进行了测试。
观察到发展至成人水平的情况如下：3岁前为低对比度单字母视力；5至6岁时为高对比度单字母视力；7至8岁时具备识别MD字母的能力；9至10岁时为字母表视力。
学龄前儿童对MD形状的识别能力持续成熟。该年龄组中LD形状的识别能力也会成熟，但时间进程不同。从发育角度来看，MD字母与低对比度字母并不等同。我们的研究结果为MD和LD形状的空间方面在一定程度上是分别处理的这一假设提供了进一步的支持。
