 As Scott said, these experimenter expectancy effects or observer effects as they're also called are really quite common. We've seen them today in facilitated communication in clever hands. And there's also a cool example called water dowsing where people use these divining rods to find water under the ground or treasure or jewels, things like that. But the dowsing rods are actually quite sensitive to the subtle movements of your hands. There's also a really cool paper by Lisa Litt that asks the question whether sniffer dogs can actually detect drugs or explosives or whether just the dogs are responding to the subtle cues of their handlers. That's right. And this is why we do experiments, right? So like Lisa Litt, you can test whether sniffer dogs can actually detect explosives. You can test whether clever hands is actually counting and doing complex mathematics. This is what we do every day. And this is why we design the experiments the way that we do, right? Take any area. I have colleagues in developmental psychology, and they're interested in measuring infant responses. Obviously, infants can't speak, but they can look. And so you might show them a picture of a face, for example, and measure how long they look at this face, compared to this face on this side. And so you simply measure how long the infant's staring at one face or you show them something odd and you measure how long they look at it compared to something else. But the people who are doing the analyses, the people who are scoring these videotapes for the looking time in infants don't know a thing about the experiment. So we talked about this blind procedure. There it is in action. So you can actually see the person who's measuring it. All they're doing is just measuring, okay, left, left, left with a stopwatch. Right. Now they're on that side. And so they can't possibly be swayed to go to one side or another, because they don't know which hypothesis they're supporting, right? I did a bunch of work in graduate school with Japanese quail. Now I won't get into the specifics of why, but we were measuring how much time they spent on either side of the cage. So they spent on this side or this side and I was there, literally with a stopwatch, measuring how long they were on one side versus another and writing down the times. And I didn't know which side of the cage they should have been spending their time on, essentially. And so that's the nature of blind experimentation, and that's why we do this. And by not knowing what's happening or not knowing what to expect, you can't possibly be swayed in the same way that you were, like the facilitators were in facilitated communication or sniffer dogs or anything else, right? That's why we designed them this way. To be intentionally naive, so you're not going to sway or influence other people. And that's one of the most important elements of the scientific method. And that's why we do it. Yep, I hope these expectancy effects are really quite familiar to people because we saw them in episode two. When you're told specific information about what to listen for, for example. So if you're told to hear, it's fun to smoke marijuana. But when you listen to Queen backwards, you will hear it. If the information is ambiguous enough, you can bend it to suit your expectations and you interpret it, you actually see here and remember it in the way that you expect based on that specific information. Now, expectancy effects play a really large and important role in forensic science. So we traveled to California to speak to Bill Thompson, who researches this stuff. He is interested in how people interpret forensic evidence like DNA. And here's what he had to say.