Controlled experiments are not only used to identify organic compounds, but are used in all fields of science. Though the use of positive and negative controls in relation to some unknown substance seems like a limited activity, it is also used in biology, psychology, as well as all other scientific fields.
An example of controls in biology can be found in ecological research. If an ecologist wanted to discover is a particular chemical in a plant is nutritionally important to a rabbit, the ecologist could use a controlled experiment. She would feed a group of rabbits food that has the chemical in question (positive control), and rabbit food without the chemical (negative control). If there is a significant change in the rabbit’s health or behavior, then she might conclude that the chemical is important.
An example of controls in psychology can be found demonstrating subliminal messages. Using two groups of people, we have them each watch a television commercial. One of the commercials has a subliminal message that says, “Buy popcorn” (positive control) and the other commercial does not (negative control). If the positive control group buys a significantly more amount of popcorn than the negative control group, then we might conclude that subliminal message do work.
These are just a couple of examples of how controlled experiments are used in science. The scientific method of using controlled experiments has led to great achievements such as landing on the moon, exploring the bottom of the ocean, and solar power energy.