Reddy Lavanya, VanRullen Rufin
California Institute of Technology, Computation and Neural Systems, Pasadena, CA, USA.
J Vis. 2007 Feb 2;7(2):3.1-17. doi: 10.1167/7.2.3.
We investigated the effect of varying interstimulus spacing on an upright among inverted face search and a red-green among green-red bisected disk search. Both tasks are classic examples of serial search; however, spacing affects them very differently: As spacing increased, face discrimination performance improved significantly, whereas performance on the bisected disks remained poor. (No effect of spacing was observed for either a red among green or an L among + search tasks, two classic examples of parallel search.) In a second experiment, we precued the target location so that attention was no longer a limiting factor: Both serial search tasks were now equally affected by spacing, a result we attribute to a more classical form of crowding. The observed spacing effect in visual search suggests that for certain tasks, serial search may result from local neuronal competition between target and distractors, soliciting attentional resources; in other cases, serial search must occur for another reason, for example, because an item-by-item, attention-mediated recognition must take place. We speculate that this distinction may be based on whether or not there exist neuronal populations tuned to the relevant target-distractor distinction, and we discuss the possible relations between this spacing effect in visual search and other forms of crowding.
我们研究了不同刺激间隔对倒置面孔中直立面孔搜索以及红绿对半分割圆盘搜索中红-绿辨别任务的影响。这两个任务都是序列搜索的经典例子；然而，间隔对它们的影响却大不相同：随着间隔增加，面孔辨别性能显著提高，而对半分割圆盘任务的表现仍然很差。（在绿色中找红色或在+中找L这两个平行搜索的经典例子中，未观察到间隔效应。）在第二个实验中，我们预先提示了目标位置，这样注意力就不再是一个限制因素：现在，两个序列搜索任务都同样受到间隔的影响，我们将这一结果归因于一种更典型的拥挤形式。视觉搜索中观察到的间隔效应表明，对于某些任务，序列搜索可能是由于目标与干扰项之间的局部神经元竞争，从而需要注意力资源；在其他情况下，序列搜索肯定是由其他原因导致的，例如，因为必须逐项目地进行由注意力介导的识别。我们推测，这种区别可能基于是否存在针对相关目标-干扰项区别进行调谐的神经元群体，并且我们讨论了视觉搜索中的这种间隔效应与其他形式拥挤之间可能的关系。
