Green (1994) page 3
Use of animals in biopsychology
This is a controversial area with several issues to be considered. These can be divided into the practical and the ethical.
As mentioned earlier, biopsychologists use animals because their methods of study cannot be used with humans. The critical point at issue is whether the study of the animal brain can tell us anything about the human brain. If not, much of the justification for using animals disappears; one could argue that the study of brain and behaviour in any species is always of interest (comparative biopsychology), but many researchers would be unhappy if these sometimes stressful procedures had no bearing at all on human behaviour and experience.
Much of the detailed evidence used to support links between animal and human biopsychology is referred to in later chapters. At this stage 1 would just like to make a couple of points. First, the mammalian brain (which would include rats, cats, dogs, monkeys, apes, and humans) is built on similar lines in all species studied. Every part of our brain can also be identified in the rat brain, although evolutionary progress means that our brain is more highly developed in terms of size and connections. The units of the nervous system (the nerve cell, or neuron) are the same in all species, and work in the same way (see Chapter 2). In fact the neurons found in the most primitive invertebrate floating around in the sea also operate in the same way. Another way of putting this is that although evolution of the nervous system has produced the highly sophisticated human brain, at the level of its basic units evolution has been highly conservative.