Crash Course Psychology #6 is where I learn about Homunculus.
For context, Crash Course inspired me to learn the basics of psychology, so I’ve made it my mission to watch the entire Crash Course Psychology playlist and paraphrase each episode in my own words. This journey wouldn’t have been possible without the Crash Course team, so many thanks to them! To showcase what I learnt, here is my personal paraphrase of episode 6:
Homunculus
In psychology, this refers to a particular sensory map of the human body, depicting the proportions in which how much we sense with them. Big hands because we touch the world primarily with hands, big mouth because of all the sensory receptors in our tongues and lips, etc. However, it’s important to note that the depiction isn’t a perfect representation of brain functions. Rather, it’s a general conceptual tool to help us better understand the relationship between our brains and our senses.
Hearing
Sounds moves in waves. These waves vibrate through a medium, like air. Of course different from the waves of electromagnetic radiation or light, but similarities include that the waves also can vary in shape. Short waves have high frequency and pitch, while long waves have a low frequency and pitch. Wave amplitude (height) determine their loudness, typically measured using decibles.
Like how our eyes can transform light into neural messages, the same is done with sound waves with our ears! And since we have 2 of them, this helps gives us directional stereophonic hearing, which is that 3D type of hearing we couldn’t experience with just 1 ear.
The hearing journey starts with sound waves entering through the outer ear. Then it gets funnelled through the ear canal into the middle ear where they cause your eardrum to vibrate. From here, the sound vibrations are amplified by our ossicle bones which comprise of the stirrup, the hammer, and the anvil. Doing so helps those very vibrations to travel to the inner ear. This is where those vibrations bump into our cochlea, causing the surrounding liquids to move, bending some of our tiny cochlear hair cells. This motion triggers neighbouring nerve cells, much like how it does with our eyes, to transform the input into electrical impulses. Except instead of light energy that our eyes got, this time its physical energy that our ears got.
Those electrical impulses travel up our auditory nerves into our auditory cortex, where the brain perceives the sounds we sensed.
Tasting
Our taste buds have taste receptor cells that read food molecules and report back to the brain. Our tongues can detect 5 distinct tastes; sweet, salty, sour, bitter, and umami. These tastes are not restricted to certain regions of our tongue.
Sensory Interaction
One sense can influence the other. For example, removing your sense of smell when biting into cold bacon makes you experience a mouthful of salt instead of bacon. It’s important for this to be moderated, as a severe case of this malfunctioning can cause unusual experiences. An example of that would be…
Synesthesia
The production of a sense impression relating to one sense or part of the body by stimulation of another sense or part of the body. In easier words, a rare neurological condition where 2 or more senses get wrapped together. This is involuntary and is experienced without planning in a durable and consistent way. It’s important to note that Synesthesia has no perfectly agreed upon definition, it has multiple valid definitions worth looking into. Either way, we don’t know why this happens, and there are multiple theories as to why;
- Theory 1: The rogue development of new neural connections may override normal boundaries that typically separate the senses
- Theory 2: All babies are born with Synesthesia and experience mixed signals until the brain matures and creates separate sense channels
- Theory 3: Neurotransmitters associated with one function turn up in a different part of the brain
All proving how we still haven’t fully understood the brain just yet.
Smelling
Unlike our sight and hearing that detect waves, our smell and taste are chemical senses. We identify smells because airborne molecules from that source travel up our noses and reach our receptor cells. They then send information to our brain’s olfactory bulb, and then travels to our primary smell cortex and parts of the limbic system responsible for emotion and memory.
Unlike our 5 (sweet, salty, sour, bitter, umami) different taste receptors or our 2 (rods & cones) types of retinal receptors, we don’t have specific smell receptors. Instead, our odour receptors come in different combinations that when distinct combinations get activated, we identify the smells we get. However, it’s important to note that how we feel about a smell, and our perception of it, is often tangled up in our experiences with that scent. Our brains are great at storing and recognising old scents by their associations. Our sense circuitry connecting to our brain’s limbic system partly explains this. It’s right next to our Amygdala (involved in memory consolidation and emotion), & our Hippocampus (central to learning and memory). This explains why scents can strongly evoke feelings and memories.
Touching
Touch is extremely important, especially in our early developmental years. Arguably, the most ‘important’ sense. The lack of it can lead to higher risk of emotional, behavioural, and social problems growing up.
Our sense of touch is a combination of 4 distinct skin sensations; Pressure, Warmth, Cold, Pain. Other skin sensations (wetness, itching, etc) are just variations of these basic 4 sensations. What’s more, different parts of your body feel different amounts of sensitivity to each of these 4 sensations.
Our sense of touch works together with sensors in our bones, joints, and tendons to provide our personal kinesthesis: the way our body senses its own movement and positioning. We use our kinesthetic sense whenever we make physical movement. This sense allows us to detect changes in the position of our body without relying on our other senses, which is why we can still know how to move around even with our eyes, nose, and ears closed.
The partner sense to our kinesthesis sense is our vestibular sense; which monitors our head’s position and our balance. Earlier we described the cochlea in our inner ear. We have our pretzel shaped semicircular canals next to that. We also have fluid-filled vestibular sacs connecting those two. Working together, they help us maintain equilibrium for our head’s position and balance.
Danniel’s thoughts on Crash Course Psychology #6
- There is an interesting parallel. In this episode, the other 4 senses were lumped together where as sight was covered in depth in the previous episode. At the same time, this episode made known that the sense of touch was potentially the most important sense. Yet, why was there a more in depth look at sight over touch? Potentially, it’s not as straightforward as the amount of screen time equating to level of significance. Maybe sight is more complicated and required more explaining, thus resulting in more screen time? I wonder what the nuanced situation was that led to this outcome? Perhaps it had nothing to do with the content, maybe it had something to do the team behind the scenes. Answers I may never find.
Enjoyed this learning of Psychology? Test your knowledge against these quick custom Kahoot! quizzes I’ve made based on the episode above: This is the easy mode and this is the hard mode for Crash Course Psychology #6.
Also, do check out what else Psychology related I’ve learnt from my Psychology blog!
Credits for Crash Course Psychology #6
Original Content & Media by Crash Course
Content Consumed and Paraphrased by Danniel Iskandar
Paraphrase Proofread by
Paraphrase Reviewed by