When doing research, many people have the strong urge to jump to a conclusion, especially one that seems very obvious. Until something is proven, it is extremely unethical to jump to a conclusion, even if one seems like a logical next step. Without the proper research in place, either done prior or with a new study, simply stating something because it makes sense is unethical and can lead to making up, or fabricating information. Another form of fabrication is when a person just makes something up and writes it down as fact, without stating it may be a hypothesis.
Plagiarizing is when someone steals another person's idea and does not give that person proper credit. It is nearly impossible to come up with an entirely new idea that no one else has ever thought of or written about, and it is fine to use that research to further develop that idea or use it as a base point for another idea, but the original research must be cited, or referenced, in the research notes.
In 1947, the Nuremberg Code and other international codes of ethics were put in place to protect research patients because of the inhumane and unethical medical research practices of 16 German physicians during World War II. The physicians were later charged with war crimes and although they haven't been the last to practice unethically, the guidelines are now in place to protect to help protect research participants. Now medical researchers must do things like ask patients to sign consent forms agreeing to the testing and known lifesaving medications can not be withheld from anyone involved in testing.
Unethical psychological research has, for the most part, stopped. But at one time psychologists experimented with the human mind in some unethical ways. Examples of this include the use of LSD for governmental use. Before the drug became popular with the counterculture, government experiments were done on military men to test the effects of the drug to see if it could be used as a weapon. The drug altered the mind so much, many of the original users were never the same.