Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany.
PLoS One. 2011;6(12):e29614. doi: 10.1371/journal.pone.0029614. Epub 2011 Dec 27.
Navigation based on chemosensory information is one of the most important skills in the animal kingdom. Studies on odor localization suggest that humans have lost this ability. However, the experimental approaches used so far were limited to explicit judgements, which might ignore a residual ability for directional smelling on an implicit level without conscious appraisal.
A novel cueing paradigm was developed in order to determine whether an implicit ability for directional smelling exists. Participants performed a visual two-alternative forced choice task in which the target was preceded either by a side-congruent or a side-incongruent olfactory spatial cue. An explicit odor localization task was implemented in a second experiment.
No effect of cue congruency on mean reaction times could be found. However, a time by condition interaction emerged, with significantly slower responses to congruently compared to incongruently cued targets at the beginning of the experiment. This cueing effect gradually disappeared throughout the course of the experiment. In addition, participants performed at chance level in the explicit odor localization task, thus confirming the results of previous research.
The implicit cueing task suggests the existence of spatial information processing in the olfactory system. Response slowing after a side-congruent olfactory cue is interpreted as a cross-modal attentional interference effect. In addition, habituation might have led to a gradual disappearance of the cueing effect. It is concluded that under immobile conditions with passive monorhinal stimulation, humans are unable to explicitly determine the location of a pure odorant. Implicitly, however, odor localization seems to exert an influence on human behaviour. To our knowledge, these data are the first to show implicit effects of odor localization on overt human behaviour and thus support the hypothesis of residual directional smelling in humans.
基于化学感觉信息的导航是动物王国最重要的技能之一。关于气味定位的研究表明，人类已经失去了这种能力。然而，迄今为止使用的实验方法仅限于明确的判断，这可能忽略了在没有意识评价的情况下，对定向嗅觉的残留能力。
为了确定是否存在定向嗅觉的隐含能力，开发了一种新的提示范式。参与者执行了一个视觉二选一强制选择任务，其中目标之前要么有一个侧一致的嗅觉空间提示，要么有一个侧不一致的嗅觉空间提示。在第二个实验中实施了一个明确的气味定位任务。
没有发现线索一致性对平均反应时间的影响。然而，出现了时间与条件的交互作用，在实验开始时，与不一致的线索相比，对一致的线索的反应明显较慢。这种提示效应在整个实验过程中逐渐消失。此外，参与者在明确的气味定位任务中的表现为随机水平，从而证实了先前研究的结果。
隐含提示任务表明嗅觉系统中存在空间信息处理。在侧一致的嗅觉线索后反应速度变慢被解释为跨模态注意力干扰效应。此外，习惯化可能导致提示效应逐渐消失。因此得出结论，在被动单侧刺激的固定条件下，人类无法明确确定纯气味剂的位置。然而，在隐含的情况下，气味定位似乎对人类行为产生影响。据我们所知，这些数据首次显示了气味定位对人类外显行为的隐含影响，从而支持了人类存在残留定向嗅觉的假设。
