Jokes aside though this argument is still upheld by some today and its actually quite interesting:
http://faculty.smu.edu/jkazez/animal%20rights/peter_harrison.htm
People laugh at the idea that animals aren't conscious but if you consider animal psychology wholly from the point-of-view of pure mimicry this argument can certainly be upheld. Animals, after all, seem to be absolutely unable to change their own behavior patterns when lacking an external incentive which would imply a lack of consciousness.
True, Harrison is one step away from some sort of creationism, but animal rights activists are often one step away from promoting the absurd argument that dolphins are more intelligent than humans.