Memoirs of Carwin The Biloquist by Charles Brockden Brown

I had taken much pains to improve the sagacity of a favourite Spaniel. It was my purpose, indeed, to ascertain to what degree of improvement the principles of reasoning and imitation could be carried in a dog. There is no doubt that the animal affixes distinct ideas to sounds. What are the possible limits of his vocabulary no one can tell. In conversing with my dog I did not use English words, but selected simple monosyllables. Habit likewise enabled him to comprehend my gestures. If I crossed my hands on my breast he understood the signal and laid down behind me. If I joined my hands and lifted them to my breast, he returned home. If I grasped one arm above the elbow he ran before me. If I lifted my hand to my forehead he trotted composedly behind. By one motion I could make him bark; by another I could reduce him to silence. He would howl in twenty different strains of mournfulness, at my bidding. He would fetch and carry with undeviating faithfulness.

His actions being thus chiefly regulated by gestures, that to a stranger would appear indifferent or casual, it was easy to produce a belief that the animal's knowledge was much greater than in truth, it was.