Where do cognitive scientists get subjects for their studies?
There is a certain amount of variation, but the workhorse of cognitive science is the Psych 100 student. At many universities, introductory psychology students are required to participate in studies (though I believe there is often an option for people who strongly object).
This is billed as an educational experience, and more or less effort is put into making it educational (I’ve been very impressed with both Harvard and MIT on this point), but it is also part of the machinery that makes the science possible.
The other option typically is to pay participants. Currently, the going rate at Harvard is $10/hour. This is supposed to be compensation for time, travel, etc., but certainly lots of undergraduates who are not currently enrolled in a psych class use it to generate pocket cash.<
One potential drawback of this system is that the motivations of the participants and of the researchers are not always aligned. The researcher typically wants to get good data; the participant may just want their $10 or course credit.
The truth is the vast majority of participants give the experiment a good faith effort, but there are always some (I’d say about 5-10%, in my experience) who just answer randomly and quickly in order to get out as soon as possible.<
There are ways to help realign the participants' and researchers' interests. One is to the program the experiment such that if you get all the answers right, you finish sooner than if you guess randomly. That makes guessing a bit less tempting a strategy. (An easy way of doing this in a computerized experiment is to have the computer respond with a long error message every time a question is answered incorrectly, with the effect that participants who make many errors take longer to finish.)