Passage 1:
1. The phenomenon being explained in this passage is the claim made by researcher David Oates that backward messages are unintentionally hidden in all human speech and can be understood when the speech is played in reverse.
2. The theories advanced to explain this phenomenon are the claims made by David Oates that any thought, emotion, or motive a person has can appear backward in human speech, and that reverse speech reveals hidden truths.
3. The most plausible theory based on the criteria of adequacy would be that there is no evidence to support the existence of reverse speech or Oates's theories. The passage mentions that there is no empirical investigation of reverse speech in any peer-reviewed journal, indicating a lack of scientific evidence.
4. The passage does not mention any specific test implication for the theory. However, a good test implication for the theory would be to conduct controlled experiments where normal speech is recorded, played in reverse, and analyzed to determine if any coherent and meaningful messages can be extracted.
5. To change my mind about my preferred theory, convincing test results would be required. This could include conducting rigorous scientific studies with a large sample size, where researchers can demonstrate that reverse speech consistently reveals meaningful messages that align with the thoughts, emotions, or motives of individuals in a statistically significant manner.