Pablo Meyer at IBM's Computational Biology Center in Yorktown Heights, New York, and his colleagues, asked 49 people to smell hundreds of molecules and rate them on intensity, pleasantness and 19 other descriptors, such as 'fruit', 'musky' and 'bakery'. The researchers gave these ratings, along with information on the substances' chemical structures, to 22 teams of computational scientists, who competed to build the best predictive, machine-learning algorithms.