"There is a lot of opposition to the use of non-human animals in psychological research. The truth is that animals are so similar to us genetically and so convenient to use that we would be foolish not to carry out such investigations."

The behavior of non-human animals is definitely perceived to be much less complex than our own, so in that respect it proves easier to study.  This is also aided by our ability to detach ourselves from them to a greater degree and so analyse objectively as well as being able to exert a greater degree of control over them.  Some types of experiments would be unethical to perform on humans, various forms of deprivation for example.

Contrary to public belief, the majority of research carried out on animals is in the form of field experiments.  This involves manipulating some part of the animal’s natural environment and raises certain ethical concerns.  Firstly, tampering with nature is questionable as disruption may have unforeseen long-term effects.  Second, ethology does not often have any direct benefit to human beings.  However, aside the sometimes stressful and invasive processes, it has improved life for pets, zoo animals endangered species etc as our understanding has increased.    

In that sense, the outcome is the greater good for the greatest number.  This is the approach taken by utilitarian argument.  If the gain (pleasure and happiness) outweighs the pain (suffering) then it is considered ethically acceptable.  It is also stated by this argument (Singer) that all sentient creatures have an equal interest to avoid pain and suffering and elevating human interests over theirs is committing speciesism.

Where utilitarianism believes it acceptable to carry out research in some circumstances, the animal rights argument believes it ought to be abolished altogether.  It is fundamental to their view that animals have rights because of their inherent value so they disserve respect and the right not to be harmed. Regardless of benefits that may be provided for humanity, the position is held that animal research should not be tolerated under any conditions and the cost-benefit approach is not sufficient to justify animal suffering.  

The guidelines for the use of animals in research have become much stricter in recent years. The 1986 Animal (Scientific Procedures) Act (an official law) safeguards the welfare of the animals being used in the important research that is allowed to take place. This ensures much more consideration and thought is put into the treatment of animals in research as failure to comply with the guidelines results in prosecution.