Driven by his own love of dogs, Charles Darwin was nagged by questions like these. To root out answers, his contemporaries toyed with dog sign language. To reveal clues, they made special puzzle boxes and elaborate sniff tests using old socks. Later, the same perennial questions about the minds of dogs drove Pavlov and Pasteur to unspeakable cruelty in their search for truth. These big names in science influenced leagues of psychologists and animal behaviourists, each building upon the ideas and received wisdom of previous generations but failing to see what was staring them in the face - that the very methods humans used to study dogs' minds were influencing the insights reflected back.