in most ways psychological research is no different than in the other scientific discipline like step one is always figuring out how to ask general questions about your subject and turn them into measurable testable propositions this is called operationalizing your questions so you know how the scientific method works it starts with a question and a theory and I don't mean theory in the sense of like a hunch that say a quad shot of espresso makes you think better instead in science a theory is what explains and organizes lots of different observations and predicts outcomes and when you come up with a testable prediction that's your hypothesis once your theory and hypothesis are in place you need a clear and common language to report them with so for example defining exactly what you mean by thinking better with your espresso hypothesis will allow other researchers to replicate the experiment and replication is key you can watch a person exhibit a certain Behavior once and it won't prove very much but if you keep getting consistent results even as you change subjects or situations you're probably onto something this is a problem with one popular type of psychological research case studies which take an in-depth look at one individual case studies can sometimes be misleading because by their nature they can't be replicated so they run the risk of over generalizing still they're good at showing us what can happen and end up framing questions for more extensive and generalizable studies they're also often memorable and a great storytelling device psychologists use to observe and describe Behavior like say the smell of coffee makes Carl suddenly anxious and irritable that obviously doesn't mean that it has that same effect on everyone in fact Carl has terrible memories associated with that smell and so his case is actually quite rare poor Carl but you would still have to look at lots of other cases to determine that conclusively another popular method of psychological research is naturalistic observation where researchers simply watch behavior in a natural environment whether that's chimps poking ant hills in the jungle kids clowning in a classroom or drunk dudes yelling at soccer games the idea is to let the subjects just do their thing without trying to manipulate or control the situation so yeah basically just spying on people like case studies naturalistic observations are great at describing Behavior but they're very limited in explaining it psychologists can also collect behavioral data using surveys or interviews asking people to report their opinions and behaviors sexuality researcher Alfred Kinsey famously used this technique when he surveyed thousands of men and women on their sexual history and published his findings and a pair of revolutionary text sexual behavior in the human male and female respectively surveys are a great way to access people's consciously held attitudes and beliefs but how to ask the questions can be tricky subtle word choices can influence results for example more forceful words like ban or sensor May elicit different reactions than limit or not allow asking do you believe in space aliens is a much different question than do you think that there is intelligent life somewhere else in the universe it's the same question but in the first the subject might assume that you mean aliens visiting Earth and making crop circles and abducting people and poking them and if how you phrase surveys is important so is who you ask I could ask a room full of students at a pacifist club meeting what they think about arms control but the results wouldn't be a representative measure of where students stand because there's a pretty clear sampling bias at work here to fairly represent the population I'd need to get a random sample where all members of the target group in this case students had an equal chance of being selected to answer the question so once you've described Behavior with surveys case studies or naturalistic observation you can start making sense out of it and even predict future Behavior one way to do that is to look at how one trait or behavior is related to another or how they correlate so let's get back to my buddy Bob who seems to think that his refrigerator is actually some kind of time machine that can preserve food indefinitely let's say the Bob is just tucked into a bunch of questionable leftovers Pizza that may very well have had a little bit of fungus on it but he was hungry and lazy and so he doused it in Sriracha suddenly he starts seeing things green armadillos with laser beam eyes from here we could deduce that eating unknown fungus predicts hallucination that's a correlation but correlation is not causation yes it makes sense that eating questionable fungus would cause hallucinations but it's possible that Bob was already on the verge of a psychotic episode and those fuzzy leftovers were actually benign or there could be an entirely different factor involved like maybe he hadn't slept in 72 hours or had an intense migraine coming on and one of those factors caused his hallucinations it's tempting to draw conclusions from correlations but it's super important to remember that correlations predict the possibility of cause and effect relationships they cannot prove them so we've talked about how to describe Behavior without manipulating it and how to make connections and predictions from those findings but that could only take you so far to really get to the bottom of cause and effect behaviors you're gonna have to start experimenting experiments allow investigators to isolate different effects by manipulating an independent variable and keeping all other variables constant or as constant as you can this means that they need at least two groups the experimental group which is going to get messed with and the control group which is not going to get messed with just as survey is use random samples experimental researchers need to randomly assign participants to each group to minimize potential confounding variables or outside factors that may skew the results you don't want all grumpy teenagers in one group and all wealthy Japanese Surfers in the other they gotta mingle now sometimes one or both groups are not informed about what's actually being tested for example researchers can test how substances affect people by comparing their effects to placebos or inert substances and often the researchers themselves don't know which group is experimental and which is control so they don't unintentionally influence the results through their own behavior in which case it's called you guessed it a double-blind procedure so let's put these ideas into practice in our own little experiment like all good work it starts with a question so the other day my friend Bernice and I were debating we're debating caffeine's effect on the brain personally she's convinced that coffee helps her focus and think better but I get all jittery like a caged meerkat and can't focus on anything and because we know that overconfidence can lead you to believe things that are not true we decided to do some critical thinking okay so let's figure out our question do humans solve problems faster when given caffeine now we gotta boil that down into a testable prediction remember keep it clear simple and eloquent so that it can be replicated caffeine makes me smarter is not a great hypothesis a better one would be say adult humans given caffeine will navigate a maze faster than humans not given caffeine the caffeine dosage is your independent variable the thing that you can change so you'll need some coffee your result or dependent variable the thing that depends on the thing that you can change is going to be the speed at which the subject navigates this giant corn maze go out on the street Wrangle up a bunch of different kinds of people and randomly assign them into three different groups also at this point the American Psychological Association suggests that you acquire everyone's informed consent to participate you don't want to force anyone to be in your experiment no matter how cool you think it is so the control group gets a placebo in this case decaf experimental group one gets a low dose of caffeine which will Define at 100 milligrams just an eye opener and like a cup of coffee's worth experimental group 2 gets 500 milligrams more than a quad shot of espresso dunked in a Red Bull once you dose everyone turn them loose in the Maze and wait at the other end with a stopwatch all that's left is to measure your results from the three different groups and compare them to see if there were any conclusive results if the highly dose folks got through it twice as fast as the low dose or Placebo groups then Bernice's hypothesis was corrected she could rub my face in it saying she was right all along but really that would just be the warm flush of hindsight bias telling her something she didn't really know until we tested it then because we've used clear language and defined our parameters other curious minds can easily replicate this experiment and we can eventually pool all the data together and have something solid to say about what that macchiato was doing to your cognition or at least the speed at which you can run through a maze science probably the best tool that you have for understanding other people thanks for watching this episode of Crash Course psychology if you paid attention you learned how to apply the scientific method to psychological research through case studies naturalistic observation surveys and interviews and experimentation you also learned about different kinds of bias and experimentation and how research practices help us avoid them thanks especially to our subable subscribers who make this and all of Crash Course possible if you'd like to contribute to help us keep crash course going and also get awesome perks like an autographed science poster or even be animated into an upcoming episode go to subbable.com crash course to find out how our script was written by Kathleen Yale and edited by Blake depastino and myself our consultant is Dr ranji bhagwat our director and editor is Nicholas Jenkins our script supervisor is Michael Ronda who is also our sound designer and our Graphics team is thought Cafe