It is well accepted that emotional intensity scales with stimulus strength. Here, we used physiological and neuroimaging techniques to ask whether human body odor—which can convey salient social information—also induces dose-dependent effects on behavior, physiology, and neural responses. To test this, we first collected sweat from 36 males classified as low-, medium-, and high-fear responders. Next, in a double-blind within-subjects functional-MRI design, 31 women were exposed to three doses of fear-associated human chemosignals and neutral sweat while viewing face morphs varying between expressions of fear and disgust. Behaviorally, we found that all doses of fear-sweat volatiles biased participants toward perceiving fear in ambiguous morphs, a dose-invariant effect generally repeated across physiological and neural measures. Bayesian dose-response analysis indicated moderate evidence for the null hypothesis (except for the left amygdala), tentatively suggesting that the human olfactory system engages an all-or-none mechanism for tagging fear above a minimal threshold.

人们普遍认为，情绪强度与刺激强度成正比。在这里，我们使用生理和神经影像技术来探究人体气味（可以传达显着的社会信息）是否也会对行为、生理和神经反应产生剂量依赖性影响。为了测试这一点，我们首先收集了 36 名恐惧反应低、中、高的男性的汗液。接下来，在双盲受试者功能 MRI 设计中，31 名女性暴露于三种剂量的与恐惧相关的人类化学信号和中性汗液中，同时观察恐惧和厌恶表情之间的面部变形。在行为上，我们发现所有剂量的恐惧汗液挥发物都会使参与者偏向于以模糊的形式感知恐惧，这种剂量不变的效应通常在生理和神经测量中重复出现。贝叶斯剂量反应分析显示了零假设的中等证据（左杏仁核除外），初步表明人类嗅觉系统采用全有或全无机制来标记高于最低阈值的恐惧。