Joseph E. LeDoux in Nautilus:
Behaviorism, which flourished in the first half of the 20th century, is a school of thought in psychology that rejects the study of conscious experience in favor of objectively measurable events (such as responses to stimuli). Due to behaviorism’s influence, researchers interested in emotion in animals have tended to take one of two approaches. Some have treated emotion as a brain state that connects external stimuli with responses.7 These researchers, for the most part, viewed such brain states as operating without the necessity of conscious awareness (and therefore as separate from feelings), thus avoiding questions about consciousness in animals.8 Others argued, in the tradition of Darwin, that humans inherited emotional states of mind from animals, and that behavioral responses give evidence that these states of mind exist in animal brains.9 The first approach has practical advantages, since it focuses research on objective responses of the body and brain, but suffers from the fact that it ignores what most people would say is the essence of an emotion: the conscious feeling. The second approach puts feelings front and center, but is based on assumptions about mental states in animals that cannot easily be verified scientifically.
When I was getting started in my studies of emotion in animals in the mid-1980s, I adopted a third approach to try to get around these problems.10 I treated emotions in terms of essentially non-conscious brain states that connect significant stimuli with response mechanisms, and feelings as conscious experiences arising from these non-conscious brain states.11 My theory, therefore, emphasized the importance of feelings, but I argued that the brain mechanisms that control emotional responses and those that generate conscious feelings are separate. By separating processes that non-consciously detect and respond to significant stimuli from those that create feelings, emotional mechanisms could be studied in animals without having to solve the problem of whether animals feel emotion, while at the same time honoring the importance of feelings in the human mind and brain.