Final answer:
The major ethical issue arising from Watson and Rayner's "Little Albert" study was the use of deception without debriefing.
Step-by-step explanation:
The major ethical issue arising from Watson and Rayner's "Little Albert" study was that deception was used without debriefing. In this study, Watson and Rayner conditioned a fear response in Little Albert by pairing a loud sound with a white rat. The study did not provide a debriefing to inform Little Albert about the purpose of the experiment, which is considered an unethical practice in psychological research.