Brain processes for “good” and “bad” feelings: How far back in evolution?

The question of whether fish can experience pain or any other feelings can only be resolved by neurobiologically targeted experiments. This commentary summarizes why this is essential for resolving scientific debates about consciousness in other animals, and offers specific experiments that need to be done: (i) those that evaluate the rewarding and punishing effects of specific brain regions and systems (for instance, with deep-brain stimulation); (ii) those that evaluate the capacity of animals to regulate their affective states; and (iii) those that have direct implications for human affective feelings, with specific predictions — for instance, the development of new treatments for human affective disorders.