The discrimination by the nose of the dog of individual human odours and in particular of the odours of twins

Summary Controlled experiments are described showing that Police dogs trained to follow human tracks, and show dogs trained to retrieve objects scented by people, can distinguish fairly reliably between the body odours of different individuals, including the members of a family. The individuality of a person's body odour as perceived by the dog's nose is not greatly dependent on the region (e.g. palm, armpit, sole) from which it emanates, although these regional odours appear quite different to the human nose. The individual odour of a person is perceived by the dog even when mixed with another person's body odour, or with some strongly smelling substances. In retrieving experiments the body odours of identical twin partners offered in succession are accepted for each other and there is no indication that the dogs perceive any difference. In tracking experiments in which two body odours are offered simultaneously and mixed up, those of identical twin partners are distinguished by the dogs. However, when the odour of one twin is offered in place of the odour of the partner, and in the latter's absence, it is picked out from the odours of other people. Thus, the odours of identical twin partners, although more similar than those of any other people tested, can nevertheless be distinguished by well trained dogs.