The other day, I had a participant who visited my lab, who acted quite weird. The sad thing is that I couldn't screen them whether they are high or not beforehand, so while most of my participants are good and therefore the data they contribute are usable, sometimes I just get weird participants who I have to deal with, pay, and yet remove from the study, as their data will be more or less corrupted and unusable.
So this guy came to my lab. I asked him a few questions in the beginning, making sure that he was eligible for the study. He sort of answered them satisfactorily. It was during the experiment itself that made me think that something was off.
So I was explaining to this person what the experiment was about. The instructions are also presented on the computer screen, which every participant can read. However, I don't just let them read it on their own, I explain it to them simultaneously. In fact, normal participants don't even read the instructions and they just listen to me, because that's probably easier. And if they wanted to read what was on the screen, they would read it after I finish explaining things.
Anyway, this person couldn't handle the fact that there was visual and auditory stimuli at the same time. I had to ask him if he had any questions, and then he blanks out, and so I would repeat the instructions to him. I told him the instructions three times. He seemed just generally zonked out so to speak.
And then when the experiment finished, I asked him if there were any patterns he noticed. A lot of participants would notice something. Whether it was something about the way the sentences were phrased, or whether there were multiple instances of a particular phrase, a normal participant would notice something. What he noticed was something totally unexpected, and basically he noticed something which if you are a normal participant, you would figure out that that part was not the experiment. It's almost like saying that he noticed that the screen's background was white.
There were supposed to be two experiments running during the hour, but after the first one, I figured that I wouldn't be able to use the data from this person, and therefore what's the point of running the second experiment when I am going to throw the data away anyway. So I said that the session is over, I paid him 10 EUR for his time, and he left.
He didn't smell of alcohol, nor of weed. But he seemed to have trouble concentrating, and whenever he was looking at me when we were talking, he seemed like he was looking through my head, looking at something behind me. My guess is that he was on a trip or something. Who knows, I don't have drug experience so what can I say?
Thankfully this doesn't happen too often.
I suppose there are pros and cons with not recruiting in the university. Since I do not work in a university setting, I don't have an easy access to Introductory Psychology students who would be potential participants. When I was in graduate school that's how I recruited my experiment participants. The negative thing about that is that your participants tend to be quite homogeneous, composed of university students 18-24 years old. My sample is broader and more heterogeneous than that, but yes, sometimes I do get flukes like these whose data I have to throw out.