Is the distance between the smell of almonds and that of bananas greater than the distance between the smell of almonds and that of roses? A new method, developed by research student Rafi Haddad under the supervision of Prof. Noam Sobel of the Neurobiology Department and Prof. David Harel of the Computer Science and Applied Mathematics Department, accurately measures, for the first time ever, the distance between different types of odors. Thus, for example, the distance between the smell of almonds and that of bananas is one and a half times greater than the distance between the smell of almonds and that of roses.
The new Weizmann technique offers scientists an important research tool for selecting appropriate odorants in olfaction experiments. It also provides the first steps toward understanding the laws that govern the sense of smell.
In order to develop their method, the researchers chose about 250 odorants usually used in olfaction experiments and generated for each molecule a long list of chemical characteristics. They then created a multidimensional map of chemical characteristics and placed each odorant in the appropriate location on the map.
The scientists used the map to predict neural responses to the 250 odors and compared these predictions to published experimental data on the actual neural responses of various lab animals to these odors. The result: a striking similarity between the predicted calculation and the actual measured responses. These results suggest that the differences between smells are universal and depend on the chemical and physical characteristics of the odor, not on each person’s individual experience or preference – a finding that contradicts the widespread opinion that smell is subjective.
Prof. Noam Sobel’s research is supported by the Nella and Leon Benoziyo Center for Neurosciences; the J&R Foundation; the Eisenberg-Keefer Fund for New Scientists; and Regina Wachter, New York, NY.
Prof. David Harel’s research is supported by the Arthur and Rochelle Belfer Institute of Mathematics and Computer Science; and the Henri Gutwirth Fund for Research. Prof. Harel is the incumbent of the William Sussman Professorial Chair of Mathematics.