I think you can usually tell by the way a person speaks or writes whether something is legit. The wording in the original post was very standard for participating in an academic study. Most spammers don't write like that; most hackers deliberately put in clues that their stuff is not legit.
Like many websites, SurveyMonkey is legitimate but may be used for nefarious purposes. I don't think it was in this case.
Good luck with your research. It would be very nice if you'd post a synopsis of your results and conclusions.