Researchers use students as their test participants when they're doing more scattershot-type research because they're a lot cheaper to work with. The cost of sa

Researchers use students as their test participants when they're doing more scattershot-type research because they're a lot cheaper to work with. The cost of sampling participants from the general public is not necessarily proportional to the expected value of the research. What's supposed to happen, then, is that any interesting findings will then be replicated using a more expensive, higher-quality study. That has kindasorta happened - there has been quite a bit of follow-up research, but it tends to still be performed on undergraduates. All that said, even if the population they studied is only undergraduates, the findings they report in the paper would still be interesting even if they were only useful for improving college-level educational programs.