Jacques Loeb (1859-1924) proposed a thoroughly mechanistic view of animal behavior, but did believe that higher animals had some semblance of consciousness.
Animals are capable, he believed, of learning and remembering simple acts. Loeb believed that it was a simple associative memory that enabled animals to react consistently to stimuli--such as going to where they previously found food.
Other researchers, such as Charles Henry Turner (1867-1923), who may have been the only African American psychologist at that time, Willard Small, who introduced the maze and use of white rats in learning experiments, and Robert Yerkes continued the investigation of animal behavior, learning, consciousness, and intelligence. Margaret Washburn (1871-1939) wrote an influential book, The Animal Mind (1910).
By the early 20th Century, there was a small but devoted group of researchers in the new field of comparative psychology. Unfortunately, they were not well supported or encouraged by their universities, where administrators saw little practical value in the study of animals (Schultz & Schultz, 2008).
Most of these researchers were primarily interested in animal consciousness. They commonly employed careful naturalistic observation and introspection by analogy, in which they observed the animals’ behavior in standard conditions and then drew inferences about the animals’ mental states. This was actually a form of introspection--that is, inferring animal conscious states based on what a human’s conscious state would be in similar situations. We can see the influence of Wundt and Titchener here.
After about 1915, when introspection in human research was being rejected, the study of animal behavior became far more objective and mechanistic. It became largely a part of the new behaviorism. Thorndike, Pavlov, and Watson all carried out animal research, as did nearly all of the behaviorists through the 1940s. Thus, behaviorism--the school that was to dominate academic psychology for much of the 20th Century--has roots in the early animal researchers, Romane, Morgan, Loeb, Washburn, and others.