Wavelength is a physical measure of light, and the intricate understanding of its link to perceived colour enables the creation of perceptual entities such as metamers-non-overlapping spectral compositions that generate identical colour percepts1. By contrast, scientists have been unable to develop a physical measure linked to perceived smell, even one that merely reflects the extent of perceptual similarity between odorants2. Here, to generate such a measure, we collected perceptual similarity estimates of 49,788 pairwise odorants from 199 participants who smelled 242 different multicomponent odorants and used these data to refine a predictive model that links odorant structure to odorant perception3. The resulting measure combines 21 physicochemical features of the odorants into a single number-expressed in radians-that accurately predicts the extent of perceptual similarity between multicomponent odorant pairs. To assess the usefulness of this measure, we investigated whether we could use it to create olfactory metamers. To this end, we first identified a cut-off in the measure: pairs of multicomponent odorants that were within 0.05 radians of each other or less were very difficult to discriminate. Using this cut-off, we were able to design olfactory metamers-pairs of non-overlapping molecular compositions that generated identical odour percepts. The accurate predictions of perceptual similarity, and the ensuing creation of olfactory metamers, suggest that we have obtained a valid olfactory measure, one that may enable the digitization of smell.

中文翻译：

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嗅觉测量可以产生嗅觉同色异谱

波长是光的物理量度，对其与感知颜色的联系的复杂理解能够创建感知实体，例如生成相同颜色感知的同色异谱-非重叠光谱组合。相比之下，科学家们一直无法开发一种与感知气味相关的物理测量方法，即使是仅仅反映气味之间感知相似程度的测量方法。在这里，为了生成这样的度量，我们收集了来自 199 位参与者的 49,788 对气味剂的感知相似性估计，这些参与者闻到了 242 种不同的多组分气味剂，并使用这些数据改进了将气味结构与气味感知联系起来的预测模型。由此产生的测量将气味的 21 种物理化学特征组合成一个以弧度表示的单一数字，可准确预测多组分气味对之间感知相似性的程度。为了评估这项措施的实用性，我们调查了我们是否可以使用它来创建嗅觉同色异谱。为此，我们首先确定了该度量的一个临界值：彼此相差在 0.05 弧度以内或更小的多组分气味剂对非常难以区分。使用这个截止值，我们能够设计嗅觉同色异谱-非重叠分子组合物，产生相同的气味感知。感知相似性的准确预测，以及随后产生的嗅觉同色异谱，表明我们已经获得了有效的嗅觉测量，