A group of researchers wants to determine how music affects people with dementia. So, the researchers team up with a hospital and monitor the brain activity of patients suffering from dementia. To avoid bias, they conduct the research when the patients are asleep, and the patients are not aware that they are being monitored. Which of the following ethical requirements was violated in this study?

Informed consent was violated in this study. Patients were not informed that their brain activity would be monitored while they were asleep, and therefore they did not have the opportunity to give their consent for participation in the study. This lack of informed consent is a violation of ethical requirements in research involving human subjects.