Animal Behaviorist Conrad Lorenz on dog lies:

It is well known that many dogs are not only physically sensitive but they love being pitied, and are quick to learn how to influence a tender-heartened person to their own advantage. During a bicycle tour…, a tendon of (my dog) Stasi’s left forepaw became inflamed as a result of over strain. Since she was extremely lame, I was obliged to walk with her for some days instead of using the bicycle. Later on, too I was very careful of her and at once rode slowly if I noticed that she was becoming tired or beginning to limp.
It did not take her long to realize this, and if I rode in a direction uncongenial to her she very soon went lame. If I cycled… to the military hospital, where she might have to remain on guard… for hours on end, she limped so pitifully that people in the road often reproached me. But if we took the direction of the Army riding school where a cross-country ride was likely to ensure, the pain had gone. The swindle was most transparent on Saturdays. In the morning on my way to duty, the poor dog was so lame that she could scarcely hobble behind the bicycle, but in the afternoon, when we covered the 13 miles to the Ketscher lake at a good speed, she did not run behind the bicycle but raced ahead of it at a gallop.