In psychology, one of the many ethical controls put in place is called informed consent, this means that before participants can take part in research they have to provide their consent.
The main problem with this is what constitutes informed consent, do we tell participants everything about our study, or only the parts we think are important. Most researchers choose to inform participants of the procedures of the study and any potential harm or benefit the study could provide, which I believe to be the correct way to go about it, because then potential participants know everything that is relevant, but you haven’t bored them with all the minute details, or providing them with a document so large that they don’t even pay attention (with an attention span like mine it’s a very real possibility).
Another issue with informed consent is the impact it can have on the validity of a study, sometimes if a participant knows, or guesses the intention behind a study, they will adjust their behaviour towards it, which can greatly skewer the results of a study and mess up an entire analysis. Though in studies where this is a serious issue, this effect can be negated by gaining what is known as retrospective consent, this means that you get consent for participation at the end of a study and provide full disclosure then, with only basic consent given at the beginning of the study. This technique was used in Milgrams study of obedience as participants had to believe they were actually causing someone harm.
Informed consent is a useful tool as it also allows us to see which studies are contentious in nature as participants will refuse consent to studies they believe are overly harmful which can also be used to test our own ethical procedures and controls.