Note GJ — Chapter IX · MENTAL PROCESSES IN ANIMALS: THEIR POWERS OF PERCEPTION AND INTELLIGENCE.
Reading edition
As I understand the observations here tabulated, the twelve cards lay always within Van's reach and sight. An ordinary untrained dog would have taken no notice of them. But Van, when he wanted food or tea, went and fetched the appropriate card, and got what he wanted in exchange. In twelve days he only made two mistakes, bringing "Nought" once and "Door" once.