Transcription
Hey there psychology students, and welcome back to the Mr. Sin channel. Today, we are going to be reviewing unit one, topic six, sensation. Now, this is the last topic review video of the unit. But fear not, I also made one unit review video that covers everything in the unit. Plus, it also comes with a study guide answer key and, of course, a bunch of practice quizzes. I also made a full practice unit exam with an all-new digital exam simulator in the Exam Slayer. And the best part is, once you finish that unit exam, it'll break down the questions for you, showing exactly which topics you missed, which ones you got down, and which ones you need a little bit more time with. Plus, it'll also give you explanations on all of the different questions, explaining why each answer is either right or wrong. But more on that later.
Before we wrap up this unit, we need to review the different concepts of sensation. So, take out your guided notes and follow along because, well, we got a lot to talk about. Now, sensation is the process of detecting information from the environment. And this is different from perception, which involves interpreting and organizing that information. But we're not going to be talking about perception now. We'll talk about that in unit two.
Sensation begins with a stimulus, which is something like a sound or smell that is strong enough to cross a threshold to get noticed by your sensory organs, such as your eyes, ears, nose, or skin. Once the sensory organ detects a stimulus, the body transduces the stimulus into a neural signal, converting the stimulus into an electrical message that your brain can understand. This conversion process is called sensory transduction. But for sensory transduction to happen, the stimulus has to be strong enough to cross the absolute threshold. The absolute threshold is defined as the smallest amount of a stimulus that a person can detect at least 50% of the time.
Speaking of detecting sensation, we also need to talk about sensory adaptation, the just noticeable difference, and Weber's law. Sensory adaptation occurs when you are exposed to a constant, unchanging stimulus over a period of time, and your sensory receptors become less responsive to it. For example, if you light a candle in a room, at first you can smell it, but as the day goes on, eventually you can no longer smell the candle. But if someone else comes into the room, they will smell the candle right away.
Now, don't confuse sensory adaptation with habituation, which is when you are repeatedly exposed to a stimulus and start to have a reduced response to the stimulus. For example, the first time someone uses a drug, they may experience a strong effect, but with repeated use, they will start to need more and more of the drug to get the same effect. And this is actually an example of tolerance, which is related to habituation in terms of decreased responsiveness. Remember, with habituation, you are learning from a repeated stimulus, which then results in a decrease in your responsiveness to the stimulus. And with sensory adaptation, you are getting used to an unchanging stimulus.
Up next, we have the just noticeable difference, also known as the difference threshold. This is the smallest difference between two stimuli that a person can detect at least 50% of the time. For instance, if you were holding a 5 lb weight and someone adds a paper clip on top of your weight, well, you probably would not notice. But if someone adds another pound to the weight, you probably would feel it.
When trying to understand the just noticeable difference, we can actually look at the Weber-Fechner law, which is the idea that for us to notice a difference between two stimuli, the two stimuli must differ by a constant percent, not a constant amount. For example, if you were holding 5 lbs and we added one pound to the weight, you would probably notice. But if you were holding 50 lbs and I added another pound, well, you probably wouldn't notice. And that's because the percentage difference is what matters, not the absolute amount.
Now, whenever we experience something in life, our senses take in a variety of information. When our sight, hearing, taste, touch, and smell work together, it is known as sensory interaction. Our senses don't operate in isolation. They constantly influence each other to help us understand and respond to the world around us. For instance, have you ever tried to eat Skittles without actually smelling them? You should actually try it. The next time you eat Skittles, plug your nose. What you will find is that each color of the Skittles, well, they all taste the same. But if you eat Skittles while smelling them, you will start to experience different flavors for the different Skittles. That's because your brain uses information both from your gustatory system and the olfactory system to interpret flavor. This is sensory interaction when one sense influences another to help your brain form a complete perception.
Now, even though it's rare, some individuals may experience synesthesia, which is a neurological condition where one sense is experienced through another. For example, a person with synesthesia might see colors when they hear music or taste flavors when they read words in a book. Essentially, one sense is automatically triggered by another, creating a cross-sensory experience.
All right, so we've been talking about sensation and detecting stimuli for a while now, but now we are going to talk about the different senses, starting out with sight. Now, to save us some time, I'm not going to break down each part of the eye. Instead, I'm only going to review the specific structures and functions that are specifically listed in the CED. But if you need an overview video of the different parts of the eye, you can check out the exclusive review video inside my ultimate review packet.
Our visual system allows us to take in and interpret visual information. When we look at a visual stimulus, we can see that light enters the eye and is focused onto the retina, a thin, light-sensitive layer located at the back of the eye. The retina contains specialized cells known as rods and cones that capture the light from the environment. Rods are what allow you to see in dim light. They do not provide any color information or fine details. While cones, on the other hand, are what allow you to see those finer details and allow for clear vision and help you see color. Rods and cones are located in the retina at the back of the eye. Rods are found mostly in the peripheral areas of the retina, while cones are densely packed in the central part called the fovea.
Once light is detected by the rods and cones, it is transduced and converted into a neural signal that is sent to the brain through the optic nerve. The brain then processes this information, forming a mental image of what we're seeing. This is critical for recognizing faces, navigating environments, and making quick decisions.
Now, having said all that, the retina though also does have a blind spot, which is located where the optic nerve exits the eye. Here, there are no photoreceptor cells to detect light, resulting in a spot of the retina that actually can't capture any visual information. But you normally do not notice this because your brain fills in the missing information from the other eye and surrounding area, which honestly just goes to show how amazing the brain is.
Okay. So when light enters your eye, it needs to be focused onto the retina. This is what allows you to clearly see. The job of focusing the light is done by the lens, and it's a process called accommodation. This is when the lens actually changes shape to help focus light depending on how far away the object is. If the object is close, then the lens gets thicker. And if it's farther away, the lens gets thinner.
Now, if the lens does not focus the light correctly, it can cause myopia or hyperopia. If when the lens focuses on the light in front of the retina and the distant objects look blurry, it's known as myopia, better known as nearsightedness. But if when the lens focuses on the light behind the retina, close objects end up looking blurry, and this is known as hyperopia, better known as farsightedness. Just remember that nearsightedness happens when the lens focuses the image in front of the retina, while farsightedness occurs when the lens focuses the image behind the retina.
All right, so that's enough talk about the eye and the retina. Now we need to explore two color theories by reviewing the trichromatic theory and opponent-process theory. The trichromatic theory explains how cones in the retina detect color. According to this theory, we see different colors by combining signals from different cones. Remember, cones are what allow individuals to detect color. People have three types of cones. Each are sensitive to different wavelengths of light. Blue cones interpret short wavelengths. Green cones interpret medium wavelengths, and red cones interpret long wavelengths. Remember, short wavelength means high frequency and cooler colors, while long wavelength means low frequency and warmer colors. And the greater the amplitude, the brighter the colors will be, while the smaller the amplitude, the duller the colors will appear. So, the trichromatic theory states that we see different colors by combining signals from these three types of cones. For example, activating red and green cones makes us perceive yellow.
Now, on the other hand, the opponent-process theory focuses on explaining how color is processed after the cones. According to this theory, once the cones detect color, that information is passed to ganglion cells. These cells are wired in a way that some neurons are excited by certain colors and inhibited by others. Color is processed in three opposing pairs: red-green, blue-yellow, and white-black. Since colors are paired, you never see a reddish-green or a yellowish-blue. The brain can only register one color from each pair at a time.
The opponent-process theory also explains the phenomenon known as afterimages. This happens when you stare at an image for a prolonged period of time. As you look at the image, the ganglion cells responding to certain colors become fatigued. Then, when you look at a neutral background, the fatigued cells do not respond as strongly, while the opposing cells become more active, creating an afterimage in complementary colors.
Now, since we are talking about colors, we also have to talk about color vision deficiency. Color vision problems typically occur when one or more types of cone cells or the ganglion cells that process color signals don't function correctly. There are two types of color blindness that you want to be familiar with. The first is dichromatism, which occurs when someone is missing one type of cone, resulting in the individual to become confused between certain colors. The most common type is red-green color blindness, where an individual has difficulty distinguishing between different red and green hues. The second is monochromatism, which happens when all cone cells are either missing or not working properly, resulting in the individual to see everything in different shades of one color, usually black, white, and gray. Since the individual lacks the ability to perceive any color at all.
All right. Now, to wrap up this sense, we are going to quickly review two vision-related disorders that can occur if the occipital lobes are damaged. The first is prosopagnosia, also known as face blindness. A person with prosopagnosia can see faces but cannot recognize who they belong to, even people they know like family members or close friends. They can still see and describe facial features but cannot identify whose face they are looking at. And the last disorder we have is blindsight, which happens when there is damage to the primary visual cortex in the occipital lobe. Individuals with blindsight appear to be blind in part of their visual field, as they cannot consciously see or respond to visual stimuli in the area. However, they still can respond to certain stimuli without conscious awareness. For example, a person with blindsight might not see a ball coming at them, but they might duck or move out of the way anyway. And this is because their brain still receives some visual information without conscious awareness.
All right. Now, I know that was a lot. So, to help make sure that you truly understand the different parts of vision, I created a practice quiz for you to use to check your understanding. The quiz is in the ultimate review packet and comes with an in-depth explanation to show you why each answer is either right or wrong and explain why that is to help make sure that you truly master this information.
Now, up next is our auditory sensory system. We can see that sound is created by the movement of air molecules. This movement creates vibrations which vary by frequency. This refers to how fast the wave vibrates and determines the pitch, how low or high a sound is. Shorter wavelengths have higher frequency and create higher pitch sounds, while longer wavelengths have a lower frequency, which create lower pitch sounds.
Now, you also need to be familiar with amplitude, which refers to the height of the wave and determines the loudness or intensity of a sound. This is measured from the wave's peak or trough to the equilibrium line.
Now, to better understand how we hear different tones, we can look at a couple different theories that help explain pitch perception. The first theory is place theory, which suggests that different pitches stimulate different places on the basilar membrane in the cochlea. This theory helps explain our ability to hear high-pitch sounds. The next theory is the frequency theory, which suggests that the auditory nerve's impulses correspond directly to the frequency of the sound wave. Essentially, the rate at which the neurons fire matches the frequency of the sound wave, which helps explain our perception of low-pitch sounds. For instance, a sound wave with a frequency of 100 hertz would cause the auditory nerve to fire at 100 times per second. Lastly, the volley theory suggests that groups of neurons take turns firing in rapid succession to match the frequency of sound, which helps explain mid-range frequencies. All of these theories help explain how we recognize music, understand speech, and even detect emotional tone in someone's voice.
All right, so those are the theories that you want to be familiar with. Now, when it comes to sound, you also need to understand sound localization. This is the ability to identify the position and changes in the position of sound sources. This is a complex process that involves the auditory system and several auditory cues to determine the direction and distance of sounds. Say a sound comes from your right side. This will result in the sound reaching your right ear slightly before your left ear. Your brain notices this small difference and uses that to locate the direction of the sound. Now, generally, the sound will be the loudest in the ear that it reaches first, since your head blocks some of the sound from reaching the other side. This creates a volume difference, which your brain will also use to locate the source of the sound. Lastly, we can see that the shape of your head and outer ears help your brain actually figure out if the sound is coming from above, below, in front, or behind you. Sound localization helps us understand where sounds in our environment are coming from and helps us complete our daily tasks and communicate effectively.
All right. Now, before we wrap up our auditory system, we need to talk about two types of hearing loss that you want to be familiar with. The first is conduction deafness, which occurs when there is damage to the outer ear or middle ear, preventing sound from being properly sent to the inner ear. The second type is sensorineural deafness, which occurs when there is damage to the inner ear or the auditory nerve. This is often caused by aging, exposure to loud sounds, or genetic factors. If individuals are experiencing hearing loss, they can get a cochlear implant, which is a device that converts sounds into electrical signals. These signals then stimulate the auditory nerve and allow for the signals to be sent to the brain. Or an individual could also get a hearing aid, which amplifies sound to allow an individual to hear different sounds around them.
Now, before we move on to our chemical sensory system, I want to remind you if you need more help with the auditory system, I created a practice quiz with explanations for each question as well, and also made a short breakdown video going over the different parts and functions of the ear. You can find all those resources inside my ultimate review packet.
Okay, so our chemical senses include our smell, which is also known as olfaction, and also taste, which is also known as gustation. These senses work by detecting chemical molecules in the air or food, and they can have a pretty big impact on our emotions, memories, and even behaviors.
Starting with smell, we can see that when you smell odor molecules, they enter your nose and bind to the olfactory receptor cells located in the nasal cavity. Once this happens, the receptors then transduce the chemical signal into an electrical signal, which is sent to the olfactory bulb in the brain. After that, the signal is sent to different parts of the brain like the amygdala and hippocampus, which explains why smell can trigger strong emotions or memory.
Now, when it comes to smell, I do want to mention pheromones. These are chemical signals released by an individual that affect the behavior or physiology of other individuals. Pheromones are detected by the olfactory system and play a significant role in communication within the same species.
All right, so that's olfaction. But remember, our chemical senses also include gustation, which is the sense of taste. When talking about taste, we can see that there are six basic tastes that your tongue can detect. There's sweet, sour, salty, bitter, umami, and oleogustus. Sweet often signals energy-rich foods. Sour can warn us of spoiled foods. Salty helps regulate our electrolytes. Bitter warns us about potential toxins or harmful food. Umami is linked to savory, protein-rich foods. And lastly, oleogustus is connected to fats and oils. We can taste these six tastes thanks to our papillae, more commonly referred to as taste buds. These small structures are located on our tongue, and they are what contain receptor cells that transduce chemical signals into neural signals, which allow for information to be sent to the brain where they are interpreted as taste.
Now, the number and sensitivity of these taste receptors often varies between people, which ends up actually creating different categories of tasters. The first one is supertasters. These are people who have a higher than average number of these taste receptors, allowing them to experience tastes more intensely. Then there are medium tasters. These are individuals with an average number of taste receptors who have a more balanced sensitivity to different tastes. And lastly, there are non-tasters, who are individuals that have fewer taste receptors, making them less sensitive to certain tastes. These individuals may not detect bitter flavors as strongly and might prefer foods with stronger flavors.
One thing to remember when it comes to taste and smell is these two chemical senses interact closely to create the full sensation of flavor. Taste buds detect the basic tastes, while the olfactory receptors identify the aromas released from the food. Together, these inputs are processed by the brain to produce the different flavors that we experience. Now, if you do need more help with taste or smell, remember to check out the practice quizzes and the other resources inside the ultimate review packet for more help and practice.
All right, up next we have our touch sensory system. Remember, our sense of touch is part of the somatosensory system. This is what allows us to detect things such as pressure, temperature, pain, and texture. Whenever we touch something, the receptor cells in the skin detect the physical stimuli such as heat, cold, vibration, or pressure.
Now, there are a variety of receptor cells that are involved with touch, but I'm only going to highlight our warm and cold receptors in this video. If you want more information on the others and a breakdown of the different layers of the skin, check out the exclusive video in the Ultimate Review packet.
When we touch something warm, it's our warm receptors in the skin that respond to the increase in temperature. And when we touch something cold, it's our cold receptors that respond, which honestly makes sense. But when we encounter something extremely hot, it can actually activate both the warm and cold receptors simultaneously. When the warm and cold receptors both activate, it sends mixed signals to the brain, which the brain then interprets as hot. This may seem odd, but it's because extreme heat actually overstimulates cold receptors in addition to the warm ones. The brain receives conflicting inputs, which then interprets it as a sensation of hot or even burning. This unusual overlap is one of the reasons why intense cold and extreme heat can sometimes feel oddly similar at first.
Remember, our sense of touch is part of the somatosensory system. This is what allows us to detect things such as pressure, temperature, pain, and texture. So, we can see that once the stimuli is detected, it is transduced. Remember, this is the process of converting the stimuli into electrical messages. Once complete, the message is sent through the nervous system to the brain where it is processed in the somatosensory cortex located in the parietal lobe.
Okay, so we've now covered how sensation of touch occurs. But now we are going to shift our focus over to the sensation of pain. Remember, pain is more than just a physical feeling. It's processed by the body and the mind. Receptors such as nociceptors, which are located in the dermis, are what help detect harmful stimuli such as extreme temperatures, damage, or chemical irritants.
One theory that looks at pain is the gate control theory, which seeks to provide insight into how the body processes pain. The gate control theory suggests that the spinal cord contains a neurological gate that can either block pain signals or allow them to pass through to the brain. This gate is influenced by the activity of different types of nerve fibers. Large diameter fibers, A-beta fibers, typically carry non-painful stimuli such as touch or pressure. Their activity can close the gate, reducing the perception of pain. On the other hand, though, small diameter fibers, A-delta and C fibers, carry pain signals. Their activity can actually open the gate, allowing pain signals to reach the brain. And we can see an individual's psychological state, attention, and other sensory inputs also influence the gate's activity. For instance, if an individual is distracted, it might reduce the pain perception by closing the gate. But when the individual becomes focused on the pain, the gate will open up and cause more pain.
Now, the last thing you need to remember when it comes to pain for AP psychology is phantom limb sensation, which happens when someone has lost a limb but still feels pain or sensations in the missing body part. This can occur due to the brain's neural map of the body, which may still include the missing limb. Even though the limb is gone, the brain and the spinal cord can still send or interpret signals as if the limb were still there, again highlighting that pain isn't just physical but also mental, being shaped by the brain.
Okay. Okay. I know this video has been really long, but we made it to our last two concepts. Now we have to talk about the vestibular sense and kinesthesis. The vestibular sense helps maintain balance and spatial orientation. Essentially, this is what allows you to stand upright. This sense is made possible by structures in the inner ear, specifically the semicircular canals and the vestibular sacs. These structures detect changes in head movement, tilt, and acceleration by sensing how fluid moves inside them. When your head moves, the fluid shifts, bending tiny hair cells that send messages to the brain. This information is sent to the brainstem and cerebellum, where it helps coordinate balance, posture, and even eye movements. This is why when you spin around and stop, you feel dizzy. Your vestibular system is still detecting movement because the fluid in your inner ear is still in motion.
On the other hand, kinesthesis is your sense of your body's position and movement. This is your ability to know where your limbs are even without looking. This sense comes from receptors in your muscles, tendons, and joints, which send constant feedback to your brain about how your body is moving and where it is in space. Kinesthesis is what allows you to walk, run, or type on a keyboard without needing to watch your hands.
So, we can see that our bodies are pretty complex, and even though our individual senses are quite amazing, it's when they come together and interact with one another where we truly experience the world around us. All right, that's it for this massive video. Now you know the drill. Go take the different practice quizzes, watch the exclusive review videos in the ultimate review packet just to make sure that you have mastered all of this content. And of course, don't forget to also check out the Exam Slayer to take a full practice exam for unit one of AP psychology using the digital exam simulator and watch the unit summary video for a complete unit review. As always, I'm Mr. Sin. Thank you so much for watching, and until next time, I'll see you.