To ask if animals should be used for experimentation, one needs to narrow down the type of experimentation being conducted. Medical research requires the use of animals to verify whether a new medicine or compound is fatal to use in humans. The development of new treatments for diseases would be extremely limited if animals were not available. Testing would have to be performed in humans with some killed unnecessarily. Psychology also has a history of using animals to test cognitive development, language, and information processing.
The need for animals in research, particularly medical research, is because of the need to determine the toxicity and dangers of new drugs. One important area is neurological disease. Researchers generally start with cell lines then move up to complex living creatures, such as a rodent. Then, depending on the drug being tested, they move to a mammal, such as a dog or monkey, before testing the drug in human trials. This is to avoid death and illness. In recent years, the system has been short-cutted, mainly due to the hassle and cost of animal research, and there have been many problems with clinical trials resulting in death or drugs being released before appropriate testing has been done on them. When the process is followed to the letter, the resulting treatments end up being prohibitively expensive in order to recoup the costs.
Though the effect of chemicals in animals does not always directly translate into what the effect will be in people, but it can give an indication of what dangers may be present. Animals are also wonderful learning tools, for researchers and medical students alike. For basic research, to understand disease, dogs are an excellent mimic of the human cardiovascular system. Before opening up a person for open heart surgery, a surgeon can practice on a dog heart. Diabetic dogs provide tissue samples for learning about genetic or enzyme deviations that lead to the breakdown of the human body as we age. Monkeys provide research models for AIDS and possible treatments for HIV. Without these animal counterparts in research, the world would all be at a loss.
I worked with mice for medical research. It was a heart-wrenching part of my dissertation research in which I had to anesthetize and vivisect a special genetic strain we had bred to study the localization of a receptor responsible for blood pressure regulation. It was done to determine the genetic implications in hypertension. And we happened upon a new discovery! One we would never have been able to find had we not had mice to work with. One that hopefully will one day translate into a drug targeting blood pressure regulation where it goes awry, adding years to many people's lives. Without mice, this would never have been possible as the organs themselves were necessary in their natural context, cells simply did not suffice. There are many regulations in place, with random inspections by regulatory agencies, to insure the proper care, handling, and pain management for research animals. Before attempting my work we had to have a written plan for each animal we were going to use; it was an outline of exact procedures from which we could not deviate. The school/facility animal committees had to approve the use of every chemical, drug, and procedure we were going to use. They in turn had to seek approval from the state agency before we could begin or even obtain the mice from the breeding facilities.
The animals used in research are well cared for, with constant clean water, food, and clean bedding. They have a normalized light/dark cycle for sleeping and are not allowed to experience unnecessary pain. Certain studies on stress can not be completed because of this requirement, so allowing animal-based research does not mean allowing all or unnecessary experimentation.