Sensation vs. Perception: What's the Difference?

Alright guys, welcome to Psych Explained. In this video, we're going to talk about two very different, yet very interrelated concepts known as sensation and perception. And these are huge terms in the field of psychology, right? Everything from how our senses work, to thresholds, to depth perception, to optical illusions, all fall under the umbrella of sensation and perception. Alright, so let's start with sensation. Steps one, two, and three. Now, right now, you have a lot of information coming into your body, right? Your nervous system is detecting, right? Sights and sounds and smells. This person is seeing a stoplight. They're detecting yummy McDonald's french fries. I'm hungry right now. And music, maybe coming from your phone, right? So, you have all this information, right? So, step one of sensation is your body has to pick up some sort of stimulus, right? Something that is stimulating your nervous system to act accordingly, right? And if we have two pieces of information, we'll use the word stimuli for plural, right? But here's what's interesting. Your eye, for example, doesn't actually see a stoplight. Every one of our senses is picking up a specific type of energy, okay? Let's think about our first one. For stimuli or stimulus, your eye is picking up what we call light waves. What is it picking up? It's picking up light waves, right? From the sun, it's emitting tons of energy, right? And this energy is bouncing off of me. It's bouncing off of objects. And we perceive this as colors and shapes and objects and things around us. And this is determined by wavelength, right? Color is determined by different wavelengths, right? That we see, right? So, in terms of energy, your eye is detecting what we call light waves, right? And what about your nose, right? You're not actually smelling fries, although I wish we were. What you are picking up, the energy, is what we call odor molecules, right? These kind of chemical bonds and each different chemical bond creates a different sort of scent, right? So, you're picking up not fries, but you're picking up odor molecules. And what about hearing? I know you think that there are words coming out of my mouth, but there aren't. It's just air and vibration. So, what's the energy you're picking up? You're sound waves, okay? I know it's weird to think that there aren't words coming out of my mouth, but just different waves, right? Sound waves are particles bouncing off each other to create this kind of energy in the air. So, here we have our sound waves coming out of your aeropause, all stuff like that, going into the ear. So, that's step one with sensation. You're picking up some sort of raw data, energy in the world that your organs are picking up. All right, what does lead us to step two? Reception. Reception is we mean there has to be some part of your organ, eye, nose, or ear, that is receiving, detecting that energy, and then causing some sort of chemical response. So, what we have to think about is what part of these organs is receiving, detecting, and causing a change in the body? Do you know which part of eye? Well, if you're thinking, and I'm going to put a little square right here, if you're thinking for the eye, there we go, a part called the retina, well, you're correct. I'm going to erase here, make it a little bigger, right? The retina. And the retina is receiving this light wave, detecting it, and eventually going to cause a change. And specifically in the retina, we'll talk about this cones and rods, right? These are photoreceptor cells we've talked about before. All right, what about in the nose? Where does reception occur? Where are we detecting these odor molecules? Well, it's going up the nose, and it's going to be detected along these little cilia right here, these little tiny hair cells. Do we know what these are called? These are called olfactory, olfaction means smell, olfactory receptor neurons. What is it called? Olfactory receptor cells or neurons, okay? And this is picking up all those molecules and chemical compounds all around us, okay? All right, what about for hearing? What part is going to detect this energy of sound or vibrations and then going to cause a response? Well, it's not the retina, it's not olfactory receptor neurons, it's this little structure here, looks like a snail, that's what it's named after, called the what? The cochlea, not Coachella, like the concert, my students will make that mistake, but the cochlea, and more specifically, something called the organ, you know where I'm going with this, organ of corti, okay? We'll talk about that a little later, okay? So, when it comes to sensing the world around us, we need some sort of energy, we need some sort of organ that's picking up that energy that's going to cause a change, and then what happens next? Well, what happens next is we need to take this energy and turn it into what? We need to turn it into electrical signals. What is this process called? Transduction, let's write this one together. What are we saying? We need to take this energy, okay, sound waves, light waves, odor molecules, whatever it is, energy, you got to spell that right, right? And turn it into what we call an action, action potential, an AP, right? This is an electrical charge, right? And transduction, a noun or a verb, transduce, occurs in all of our senses, right? Your brain doesn't understand language. You know what your brain understands? Electrical signals. So, everything has to turn into some sort of electrical signal. So, what does this have to do with that? Well, where does this energy turn into action potentials? Well, it turns into it between this microscopic space between two neurons, okay? Do we know what that's called? If you're thinking synapse, you're correct. And what we're looking at right here, I'll use a different marker, is this microscopic space is that synapse between two neurons. So, let's think about this together with all three of our senses. What is the process of going from electricity to reaching the brain, right? Where are these action potentials traveling through to reach the brain in order to be perceived, right? Understand this process. Let's start the eye first. All right. So, where does reception occur in the eye? We've already talked about it. It occurs in a part called the retina. Retina, okay? And the retina, by the way, is the entire back of the eye, right? We go through our cornea or pupil or lens. The retina is the back of the eye. And more specifically, we have cones and rods, right? And cones are very sensitive to colors and bright lights. And rods are very sensitive to dim lights, right? So, we're going to have action potential with rods when it gets really dark, right? So, that's going to cause all these neurotransmitters to be released in the synapse and bind to receptors on the next neuron. All right, where's it going to go next? Well, after the eye, and by the way, I'll draw it here. Here's our retina on the back of the eye. This is going to travel, these action potentials, to the next structure, the optic nerve, right? This is the nerve that takes information away from the eye. So, we're going all the way up here, right? And then where is that information going to go next? Well, it's going to go flow to a very important structure I have a video about, I'd love for you to watch as well, called the thalamus. So, this is going to synapse with the thalamus, you have two of them, so thalami, right in the middle of the brain. This is the sensory processing station, right? It's like, hmm, I got information, where should I send this to? What should I do with this information, right? And from the thalamus, it's going to make its final destination to the visual cortex, the primary visual cortex, where is it located? In the occipital lobe, okay? So, we're going to have our final synapse in the occipital lobe in the back of the eye, in the back of the brain, called the what? The visual cortex, okay? So, here's the flow of transduction for vision. All right, let's do smell. We start with what? Olfactory receptors, I'll use a different marker for this one, we have olfactory receptor neurons, a little N right there, all right? So, we pick up that smell, the olfactory molecules are stimulating, they're binding to the receptors, and then what it's going to do, it's going to communicate with this structure right here, okay? This is a really important structure called the olfactory bulb, I guess maybe because it kind of looks like a bulb, right? So, you have all these, you know, cilia that are connected with these axons, it's going to communicate going upward, right, to the olfactory bulb where processing is going to start, right? What am I smelling, right? What is this odor molecule, this chemical bond that I'm interpreting, right? All right, so just like the visual cortex, we are going to make our way to what we call the olfactory cortex, olfactory cortex, or maybe the primary olfactory cortex, right? Which is right here, okay? Now, on this diagram, it looks like it's on top, the lateral side, but it's not, it's actually underneath the brain. Actually, let me get the brain to help us out here, right? If we take a look at the brain, here's me, right? Here's my frontal lobe, my temporal lobe, my occipital lobe at the back, my parietal lobe on top. If we kind of turn our frontal lobe over, you're going to see this olfactory tract, right? And it's right underneath the frontal lobe, which is going to lead from olfactory tract to olfactory cortex right underneath the inferior part of the temporal lobe. So, what we're looking at right here is really underneath the temporal lobe to make sense of the smells around us. Now, it might look like we're done here, right? We're done with olfactory cortex like we were done with visual cortex, but smell is very interesting. All of our senses, except for smell, bypass through the thalamus, right? But smell doesn't. It bypasses the thalamus and goes straight to what we call our limbic system. Oh, I got a great video on that. I hope you watch it. Our limbic system, right? This is our center of emotions and memories and drives because smell is very evolutionary. This used to be one of our most dominant senses. So, smell is also going to communicate not just, of course, with the cortex, but to communicate with structures like the hippocampus. Use a different marker for that. The hippocampus, right? This is going to help us detect what a smell is. Like, hmm, have I smelled this before? This is part of explicit memories. And a really important structure called the amygdala. Amygdala. And this helps trigger fear and strong emotions, which sits right next to the hippocampus as well, right? Because if you're smelling things like fire, you're smelling rotting food, your evolutionary brain is like, danger, danger, danger. I need to run away. So, it's important to know that we don't just interact with our olfactory cortex. We're also interacting with our limbic system, okay? Limbic system. All right. So, what about our last sense? Hearing, right? How do we go from detecting sound waves to our organ of corti to reach in the brain to be perceived? Well, let's write this in together. First, we have the cochlea, right? This is the snail-like structure that we talked about before. There's my cochlea. And the cochlea is filled with all this fluid, right? And within the cochlea, you know, this fluid, is a structure called the organ. Organ of what? Organ of corti, right? And if I kind of drew it, there's kind of like three different chambers within an organ of corti. And with one of them, there's all this cilia. Have we heard the word cilia before? I know we have, right? Cilia is on our olfactory receptor neurons. The cilia is going to start moving in the wind, so to speak, when the fluid starts moving. This is going to cause what? Transduction and action potentials. We want that fluid to move, the basilar membrane to move, and then the cilia is going to cause an action potential. So where's that information going to go to? Well, after hearing, it's going to go up via the auditory nerve, right? Just like our optic nerve, right? We have auditory nerve, optic eye, auditory ear, and it's eventually going to make big structure right here, right? The thalamus, like we talked about before. The thalamus, it's going to synapse with the thalamus. And finally, synapse and make its way to where? To the auditory, what? The auditory cortex, okay? Auditory cortex, right? It's not done yet, but this is our kind of final destination, right? So with all of our senses, we want to think about what energy are we taking in, where are we receiving that information that's going to cause a change, and then the action potentials as we travel from one neuron to the next in order to be processed, okay? This is what we mean by sensation, taking in data, making sense of it, right? We could also call this process bottom-up processing. You might have heard that expression, taking information from the bottom up, and then until it reaches the brain. All right, so now we kind of move to our last stage. Remember, I talked about this as a process, not definitions, what we call perception. We've sensed the world, we've taken raw data, what is interpretation? Well, your brain has to understand what energy it's detecting, right? What are these signals that my nervous system is taking in? This is what we mean by perception. We're trying to make sense of, organize, and interpret all this information, right? So here's, for example, once information reaches the visual cortex, it's going to synapse and talk to other structures of the brain, right? What might it talk to? We talked about this structure, the hippocampus, right? This is memory, it's like, have I seen this before, right? Oh, I've seen a stoplight before. Yes, this happens instantaneously, but you have to think about it in that way, okay? So I've seen this before, I know what it is, I'm going to interpret the signal as, I'm going to interpret it as a green, green equals go, you know, like red equals stop, yellow equals, what does it mean? Pause, something like that, right? So we're interpreting and making sense of whatever it is we're saying. This is what we mean by perception. So instead of bottom up, we're talking about top down processing. All right, what about for smell? Now, even though your nose is picking up odor molecules, it doesn't know what it's actually picking up. It's not until it connects to the hippocampus and other regions, your brain's like, oh, those are french fries. Mmm, very hungry, right? Oh, those are McDonald's french fries. They're delicious. I know that's right. You ever smell something like, oh, I know what that is. Immediately, you know it's french fries, right? And then for hearing, we've reached the auditory cortex. And then once again, we're going to kind of communicate to other parts of the brain, like the hippocampus. What am I actually hearing, right? It's not just sound waves and energy, but it's, oh, oh, I'm in the car with my wife. It's Taylor Swift, right? I must be driving with my wife, right? She likes Taylor Swift. So I'm actually knowing what I'm actually listening to, not just sound waves and energy, right? So this is what we mean by sensation perception. Let's do a nice little end recap. We detect a stimulus in the form of an energy, light wave, odor molecule, sound waves. Part of our organs has to receive this information, right? Some sort of receptor that causes a chain reaction, retina in the eye, olfactory receptor neurons in the nose, cochlea slash organocorti in the ear. And then we have to have transduction. We have to turn this energy into some sort of message your brain understands, an action potential. Think about the process, the flow as we go from one part to the next. And then finally, we have to make sense of this information, which we call perception. Have I seen this before? Do I know what it is? Ah, this is perception. All right, guys, thanks for watching. I really hope you learned something. Don't forget to like the video, subscribe, write something in the comments below. I'll see you next time.