Mack Michael L, Palmeri Thomas J
Center for Learning and Memory.
Department of Psychology, Vanderbilt Vision Research Center, Vanderbilt University.
J Exp Psychol Gen. 2015 Jun;144(3):551-69. doi: 10.1037/a0039184. Epub 2015 May 4.
We explore a puzzle of visual object categorization: Under normal viewing conditions, you spot something as a dog fastest, but at a glance, you spot it faster as an animal. During speeded category verification, a classic basic-level advantage is commonly observed (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976), with categorization as a dog faster than as an animal (superordinate) or Golden Retriever (subordinate). A different story emerges during ultra-rapid categorization with limited exposure duration (<30 ms), with superordinate categorization faster than basic or subordinate categorization (Thorpe, Fize, & Marlot, 1996). These two widely cited findings paint contrary theoretical pictures about the time course of categorization, yet no previous study has investigated them together. We systematically examined two experimental factors that could explain the qualitative difference in categorization across the two paradigms: exposure duration and category trial context. Mapping out the time course of object categorization by manipulating exposure duration and the timing of a post-stimulus mask revealed that brief exposure durations favor superordinate-level categorization, but with more time a basic-level advantage emerges. However, these advantages were modulated by category trial context. With randomized target categories, the superordinate advantage was eliminated; and with only four repetitions of superordinate categorization within an otherwise randomized context, the basic-level advantage was eliminated. Contrary to theoretical accounts that dictate a fixed priority for certain levels of abstraction in visual processing and access to semantic knowledge, the dynamics of object categorization are flexible, depending jointly on the level of abstraction, time for perceptual encoding, and category context.
在正常观看条件下，你能最快地将某样东西识别为狗，但一眼看去，你能更快地将其识别为动物。在快速类别验证过程中，通常会观察到经典的基本水平优势（Rosch、Mervis、Gray、Johnson和Boyes-Braem，1976），将其分类为狗比分类为动物（上级）或金毛寻回犬（下级）更快。在超快速分类且曝光持续时间有限（<30毫秒）的情况下则出现了不同的情况，上级分类比基本或下级分类更快（Thorpe、Fize和Marlot，1996）。这两个被广泛引用的发现描绘了关于分类时间进程的相反理论图景，但此前没有研究将它们放在一起进行调查。我们系统地研究了两个实验因素，它们可以解释两种范式下分类的质的差异：曝光持续时间和类别试验背景。通过操纵曝光持续时间和刺激后掩蔽的时间来描绘物体分类的时间进程，结果表明短暂的曝光持续时间有利于上级水平的分类，但时间越长，基本水平优势就会出现。然而，这些优势会受到类别试验背景的调节。对于随机的目标类别，上级优势被消除；而在其他方面随机的背景下，仅对上级分类进行四次重复，基本水平优势就被消除了。与那些规定视觉处理和语义知识获取中某些抽象水平具有固定优先级的理论观点相反，物体分类的动态是灵活的，共同取决于抽象水平、感知编码时间和类别背景。
