Whether or not the observer/observed duality occurs in some nonhuman animals is an interesting question (perhaps with no clear answer). Many mammals and birds can develop distinct personalities that are obviously conditioned through past memory - which would be the ground for any potential observer duality - but it is highly unlikely that this has developed anywhere near the extent that it has done in humans.
However, that animals apart from humans exhibit vigorous mental activity is not in dispute (for instance even chickens have REM sleep, some parrots are able recall hundreds of human words and even assess their meanings, chimpanzees can count and subtract, elephants show clear evidence of empathy for non-elephant species, etc).
So clearly a continuity of life across human and nonhuman animal species exists; meaning that everything we see in ordinary human beings - whether at the level of anatomy, chemistry, physiology, genes, and even psychology - can be shown to have its antecedents and predecessors in the animal kingdom.
However the essential point here is that the sensory systems of pain and pleasure in particular (which humans share with animals) are truly ancient.
While it is true that most animals are very stoic in their endurance of pain, and do not (usually) suffer from complex mental suffering that compounds physical pain in human beings, their physiology, nervous and sensory responses, are on a continuum with human pain and suffering.
Obviously the degree of sensation (of pain or pleasure) that may exist in fish or crustaceans is at the polar opposite end of the spectrum from that which exists in more advanced nervous systems like ours (or those of dogs, cats and chimpanzees). Perhaps a better word for the so-called âpainâ that a shrimp might possess would be disturbance, or at most vague shock or distress.
But basic anatomy, chemistry, physiology and genetics show a clear continuity in the phenomenon of animal sentience (i.e. of pain/pleasure) - and I would suggest that it is only anthropocentrism (or speciesism) that denies this.
As the Buddhist monk Matthieu Ricard has written,
âAsserting that animals do not have consciousness is nothing other than the continuation of the Christian and Cartesian idea according to which animals do not possess a soul.â