Think back to the last time you had a feeling-all-the-feels moment.

Maybe it was when you finished reading this really great book about,. I dunno, two teenagers with cancer who fall in love, and it basically ripped your heart out and what?

I'm not sobbing, you're sobbing! Or maybe it was when you got engaged, or that day when everything went wrong. Whatever it was, it gave you some really strong feelings.

But how did you know what you were feeling? Feeling that something is hot or cold or a soft, fluffy kitty makes intuitive sense. You're touching a physical thing, and it's going to feel a particular way.

But emotions are way less straightforward. So where do they come from? Let's just say that psychologists have all the feels about that one. [INTRO ♪].

Even defining emotion is tricky. Like, we all know that cold is a feeling and that it isn't an emotion the way sadness is, but it's hard to explain the difference. So one of the things psychologists have tried to do is identify a few key parts of experiencing emotion.

There's obviously the part where you feel, along with a cognitive piece, which involves being aware of the feeling. There's also something motivational, like when fear makes you want to run away from the giant hairy spider in your basement as fast as your legs will carry you. Then there's a physiological response, like the racing heart and sweaty palms that accompanies said fear.

And there's a motor response—say, when you do actually hightail it out of there. The debate is really about which of these components are part of the emotion itself and which are a cause of it or a consequence of it. It's kind of a chicken-and-the-egg situation.

What causes what, and is there an order in which things happen? Over the years, psychologists have come up with a bunch of different theories about this. The James-Lange theory, proposed in the late 19th century, says that a physiological response happens when you perceive something, and the emotion is your reaction to that response.

So it's not that you cry because you're sad, you're sad because you cry. This is actually pretty similar to a more recent theory, known as the facial feedback theory. It argues that the way you're holding your facial muscles when you make facial expressions can actually cause you to feel emotions more strongly.

But … there were a lot of criticisms of the James-Lange theory. The biggest problem was that particular physical responses don't always indicate the same emotions. You can tremble from fear, sure, but also from rage or from cold.

So how do you tell which emotion is supposed to come from the physical response? Maybe you're really just super angry at that spider. The Cannon-Bard theory, which was proposed in the 1920s, was pretty much a rebuttal to James-Lange.

It argues that emotional responses are too fast to be the result of a physical reaction that happens first. Instead, it suggested that the physical response and subjective experience of emotion happen in parallel, at the same time. When you first see the spider crawling out from the corner, sensory information about the encounter arrives at your thalamus, a region of the brain involved in coordinating signals.

Then, the thalamus sends out a signal to your peripheral nervous system that triggers all the physical stuff and also sends the signal that triggers all the feels. That would explain why the physical response happens at the same time as you feel the emotion. And if they're separate signals, it would also explain why trembling when you're cold doesn't necessarily make you afraid.

But neither of those ideas—that emotions follow a physical response, or that they happen in parallel—say anything about how your actual thoughts play into all this. That's where the two-factor theory of emotion comes in— also known as the Schachter-Singer theory, after the researchers who first proposed it in the 1960s. The idea is that we use circumstances to attribute our physical reactions to certain emotions.

Those are the two factors: your physical response and how you label it. If your heart's pounding and that spider's ominously crawling towards you, you know to interpret that as fear. But if you're heart's pounding because you've just been to the gym and there's no spider, then you're probably good.

No fear necessary. To put their theory to the test, the researchers injected people with adrenaline, then put them in situations that were either supposed to make them laugh or make them feel super frustrated and angry. Subjects who knew that the adrenaline would give them a racing heart and sweaty palms didn't report feeling any emotion, because they blamed their reaction on the drug.

But if they didn't know, they attributed feeling all jumpy to the situation they were put in, hilarious or upsetting, and reported feeling real emotions associated with those scenarios. In the decades since Schachter and Singer first proposed their idea, researchers have come up with other cognitive theories of emotion, too. Some of them aren't as focused on interpreting a physiological response.

Instead, they argue that your emotions depend on what you think the impact of a situation will be. For example, you might get angry when you judge that you've been treated unfairly. So, there are lots of different theories for how our emotions work.

But it's hard to know whether any of them can fully explain how and why we feel the things we do. Emotions are just … messy, and whatever objective measures of emotion you might want to use in experiments, like heart rate, don't always line up with what someone's actually feeling. But the next time you run into that spider in your basement, at least you'll have some idea of how your feelings might be connected to your physical response and cognition.

Something to think about while you're running back up the stairs. Thanks for watching this episode of SciShow Psych! If you're interested in learning more about the mix-ups that can happen when you feel emotions, you can check out our episode about how you can sometimes mistake fear for love. [OUTRO ♪].