Buzz
No matter your skin color, place of birth, wealth, age, health, or uniqueness, every person in the world shares a natural set of instinctive behaviors. These behaviors, including various reflexes, are present universally. Scientists are constantly exploring the purpose of these instincts, forming theories about their functions. While many remain unexplained, these reflexes are often considered part of human evolution. This article focuses on reflexes in adults, excluding the basic primitive reflexes found in infants.
Primitive reflexes are typically exhibited by infants but are absent in neurologically healthy adults. Some well-known examples are the Palmar grasp reflex, where babies instinctively curl their fingers around anything that touches their palms, and the swimming reflex, which causes an infant to paddle and kick when placed in water. Another is the rooting reflex, which helps infants turn their heads toward anything that brushes their cheek or mouth, aiding breastfeeding, up until the age of four months.
10. Post-Micturition Convulsion Syndrome
Post-micturition convulsion syndrome (pee shivers) is a phenomenon where individuals feel a shiver running down their spine after urinating. This sensation can trigger a brief muscle twitch, a type of myoclonus, which is the involuntary twitching of muscles. While muscle twitching is a normal occurrence, particularly when people are falling asleep, pee shivers remain a puzzling phenomenon that is not fully understood by the medical field. Though not every man experiences it, it is a common report among men worldwide, and only a small percentage of women have described similar occurrences.
Some researchers believe that pee shivers may be connected to the drop in blood pressure that occurs after urination. Others propose that it could be a response to the body losing a small amount of warm fluid. The most widely accepted theory ties the phenomenon to the parasympathetic nervous system, which controls functions during rest, such as urination, digestion, sexual arousal, and salivation. However, this theory does not fully explain why only a fraction of the population experiences this phenomenon. Comedian George Carlin humorously commented on this: “pee shivers date back to pre-civilization days when men hadn’t learned to do their own shaking.”
Interesting Fact: It’s important not to confuse pee shivers with micturition syncope, which refers to feeling faint after urination. People affected by micturition syncope experience symptoms such as pallor, nausea, sweating, and loss of consciousness. This condition accounts for 2.4 to 8.4 percent of adult fainting incidents. It often happens after someone has been asleep for a prolonged period. Some individuals report dizziness or a loss of balance while urinating at night, but they don’t lose consciousness.
9. Prisoner’s Cinema
The Prisoner's Cinema is a phenomenon commonly reported by individuals who have been kept in complete darkness for extended periods, particularly prisoners in solitary confinement. It's also been experienced by truck drivers, pilots, and deep meditators, and astronauts have encountered a similar effect in space. The visual experience involves flashes of light, often in various colors, emerging from the darkness. These lights are said to take on distinct shapes that are difficult to describe and may even take on human form. Scientists believe this phenomenon results from phosphenes and the psychological impact of prolonged darkness exposure.
Phosphenes are the visual sensations of light that appear without actual light entering the eye. In 1970, scientist Oster suggested in *Scientific American* that this phenomenon could explain some “ghost” sightings. Some researchers have also linked the lights to Neolithic cave paintings, suggesting a possible connection. Ancient Greek philosopher Pythagoras is said to have sought wisdom through visions in complete darkness, retreating into pitch-black caves for this purpose.
Interesting Fact: A similar occurrence, known as the Ganzfeld effect, has been reported for centuries. It happens when a person experiences hallucinations or a sudden loss of vision after staring at a uniform field of color, not just black. Arctic explorers, exposed to endless white snow, also experienced altered mental states and hallucinations. The Ganzfeld effect is thought to be caused by the brain amplifying neural noise in the absence of visual input, similar to the process of dreaming during sleep due to sensory deprivation.
8. Knismesis and Gargalesis
Tickling refers to the act of touching certain parts of the body to provoke involuntary twitching and laughter. The terms knismesis and gargalesis are used to describe two distinct types of tickling, both of which were defined by psychologists G. Stanley Hall and Arthur Allin in 1897. Knismesis is the lighter, more delicate type of tickling that doesn’t generally induce laughter in humans. It is often accompanied by a sensation of itching and requires only a small level of stimulation, such as a gentle touch or an electrical current. Knismesis can also be triggered by insects crawling on the skin, which often leads to scratching.
Gargalesis, on the other hand, is the type of tickling that results in laughter. It involves the application of repeated, high-pressure touch to sensitive areas of the body. While often associated with play and joy, gargalesis can be very unpleasant and even torturous if prolonged. Both humans and primates are susceptible to this type of tickling. It is believed that the differences in the two sensations are due to separate itch and touch sensors in the body. Interestingly, while people can trigger knismesis on themselves, they cannot induce gargalesis on their own, a phenomenon that remains puzzling.
Interesting Fact: Tonic immobility is a state of temporary paralysis observed in animals. Certain sharks, for example, can be induced into this paralyzed state for up to fifteen minutes. This is done by lightly rubbing the sides of the shark’s snout, essentially applying knismesis. In 1997, off the coast of California at the Farallon Islands, a female orca was observed using this technique to paralyze a great white shark. The orca kept the shark immobile for fifteen minutes, eventually causing it to suffocate. This marked the first documented instance of a predator species, other than humans, hunting a great white shark.
7. Blushing
Blushing is the involuntary reddening of a person's face, often triggered by embarrassment or emotional stress. It is frequently linked to romantic feelings or certain emotional moments across various cultures. While similar to blushing, flushing involves a more widespread reddening of the skin across the entire body. Blushing can occur in nearly any situation and typically lasts for one to two minutes. For some, intense blushing can lead to self-consciousness, making them uncomfortable in certain situations. Studies have shown that blushing is caused by an overactive sympathetic nervous system.
When blushing occurs, the sympathetic nervous system causes blood vessels to dilate, allowing blood to flood the skin and turn the face red. In some cases, the ears, neck, and upper chest may also redden. The reaction can also make the face feel warm to the person. Several theories have been proposed to explain blushing, with one study by Crozier in 2010 suggesting that blushing is a visible response linked to the body's basic fight-or-flight mechanism. Charles Darwin described blushing as 'the most peculiar and human of all expressions.'
Interesting Fact: Alcohol flush reaction is a condition where an individual’s face and body redden after drinking alcohol. This flushing occurs due to the build-up of acetaldehyde in the body. Acetaldehyde is produced when ethanol is oxidized and is believed to contribute to the symptoms of hangovers.
6. Refractory Period
In human sexuality, the refractory period refers to the phase of recovery following orgasm during which it is impossible to achieve another orgasm. During this time, most men cannot maintain or obtain an erection, and the penis may become hypersensitive, with stimulation often feeling painful or uncomfortable. This effect is associated with the hormones oxytocin and prolactin. The length of the refractory period varies across different species, ranging from a few minutes to several days. Unlike men, most women do not experience a refractory period immediately after orgasm, although some do report experiencing it. Research suggests that a 20-year-old may have a refractory period lasting around 15 minutes, while those in their 70s may take up to 20 hours.
Interesting Fact: After sexual intercourse, some people experience a feeling of sadness known as post-coital tristesse (PCT). This sensation is more common in men than women and was first described by philosopher Baruch Spinoza in 1677. Comedian Russell Brand explained it as feeling an overwhelming existential dread, saying: 'It’s like, Oh my God, what have I done? A sense of profound existential angst, a sense of loss, and a sense that somehow I’ve let my mum down.' Another phenomenon related to sexuality involves males having difficulty controlling their urination after intercourse, a topic addressed in the Jim Carrey film Me, Myself & Irene.
5. Cold Chills and Spine-Tingling
A cold chill is a tingling sensation accompanied by a feeling of cold, often accompanied by a shiver. Unlike regular body chills caused by temperature, menopause, anxiety, or illness, cold chills are triggered by strong emotions. They can happen when someone is deeply moved by music, a speech, a video, or a memory, and typically result in goosebumps. A similar feeling is spine-tingling, which occurs when a person is startled by an event or experiences intense emotion. This sensation may occur spontaneously or even moments before it happens, much like the urge to yawn or sneeze. Like cold chills, spine-tingling sensations can also cause goosebumps. Some individuals are able to trigger the spine-tingling feeling without being scared.
Interesting Fact: Goosebumps appear on a person’s skin when exposed to cold temperatures or in response to strong emotional triggers such as fear, nostalgia, pleasure, awe, admiration, or sexual arousal. They occur when the tiny muscles at the base of each hair contract, causing the hair to stand up. In animals with fur or hair, this erect posture traps air, creating an insulating layer. Goosebumps can also arise from anger or fear. In animals, the raised hairs make them appear larger, which serves to intimidate potential threats.
4. Emotional Contagion
Emotional contagion refers to the tendency of individuals to pick up on and experience the emotions of those around them. This phenomenon is closely related to mob psychology and can be connected to the bandwagon effect, a well-known form of groupthink. The bandwagon effect describes how people’s behaviors and beliefs spread in a manner similar to trends or fads—when more people believe in something, others tend to follow suit. Emotional contagion is especially evident in children: for instance, when a parent feels sad, their child will often notice and respond with crying.
Emotional contagion spans a wide array of emotions, including feelings of power, strategy, invincibility, and dominance. The ability to transfer emotions between people is inherent to human nature. This phenomenon is crucial to understanding some of the most significant forces in the world, such as religions, dictatorships, and the history of war. Unlike cognitive contagion, which is more deliberate, emotional contagion operates on a more automatic, subconscious level, relying mostly on non-verbal cues, although it has been shown to occur even over telecommunication.
Interesting Fact: Folie à deux is a psychiatric condition where one person's delusions are passed on to another individual. This syndrome was first described in 19th-century France. It shares similarities with Stockholm syndrome, a phenomenon where hostages begin to sympathize with their captors. One of the most infamous examples of folie à deux is the relationship between Adolf Hitler and the Nazi Party.
3. Mammalian Diving Reflex
The mammalian diving reflex enables humans to stay submerged underwater for longer durations. While this reflex is most pronounced in aquatic mammals, humans exhibit it as well. It is triggered specifically when cold water comes into contact with the face. Water temperatures above 21°C (70°F) do not elicit this reflex, nor does submerging body parts other than the face. Upon contact with cold water, the body’s heart rate slows by 10-25%, and blood circulation to the limbs is reduced to conserve oxygen. At greater depths, the body intentionally allows fluid to fill the lungs and chest cavity, protecting vital organs from the crushing effects of pressure.
The mammalian diving reflex significantly enhances survival chances during accidental immersion. It helps prevent drowning, even in unconscious individuals before entering the water. This reflex enables people to survive for longer in cold water, without oxygen, than on land or in warm water. Interestingly, the diving reflex diminishes as people age. Children are more capable of enduring extended periods in cold water. This reflex is particularly robust in aquatic mammals like seals, otters, and dolphins, who spend a lot of time submerged. However, it remains uncertain if the reflex is triggered in extreme cold weather outside of water.
Interesting Fact: The mammalian diving reflex has inspired some proponents of the aquatic ape hypothesis, which suggests that early human ancestors adapted to life in the water. This theory contrasts humans with other great apes and draws parallels between humans and aquatic mammals. It argues that various human traits support this hypothesis, including hair loss, hair placement, subcutaneous fat in infants, a lowered larynx, a specialized nose, voluntary breath control, the waxy coating on newborns, and the mammalian diving reflex.
2. Vestibulo-Ocular Reflex
Ever wondered how humans manage to turn their heads while keeping their vision focused? The vestibulo-ocular reflex (VOR) allows for this by stabilizing images on the retina. It achieves this by causing the eyes to move rapidly in the opposite direction of the head's movement. For instance, when the head moves to the right, the eyes shift to the left, and vice versa. The VOR is crucial because humans make constant small head movements. A person with a malfunctioning VOR may struggle with reading, as even slight head movements will blur the text.
The VOR functions even in complete darkness or with the eyes shut. It's one of the quickest reflexes in the human body, with the eyes lagging behind the head by less than 10 milliseconds. Doctors can test the VOR with the caloric reflex test, which involves injecting cold or warm water or air into the ear. This action triggers the VOR reflex automatically. A healthy cerebellum is essential for proper eye movement in the VOR. Damage to the cerebellum can lead to significant issues with visual comprehension.
Interesting Fact: Have you ever wondered why drinking and driving is so dangerous? Consuming ethanol (alcohol) can interfere with the vestibulo-ocular reflex (VOR), which severely impairs your vision. As your intoxication level rises, your ability to see clearly decreases, causing your vision to become more blurred.
1. Yawning
Yawning is an instinctive human response. It involves inhaling air, stretching the eardrums, and then exhaling forcefully. This action is often linked to fatigue, stress, lack of stimulation, or boredom. Yawning is one of the most puzzling functions in humans. It can be contagious, triggered by seeing or hearing someone else yawn, or even by talking to someone on the phone who's yawning. Numerous theories have been put forward to explain why animals yawn, but none have been conclusively proven. One theory suggests that yawning happens when the blood has too much carbon dioxide and needs more oxygen, but other studies show that yawning actually reduces oxygen intake.
Another theory suggests that yawning helps regulate brain temperature. It has been proposed that a yawn may affect blood pressure in the brain. This theory is supported by the observation that people often feel the urge to yawn when experiencing rapid changes in altitude. Another possible explanation for yawning is the instinct to stretch the muscles. Contagious yawning might serve as a method for a group of animals to stay alert, passing a reminder from one member to the next. Anecdotal evidence also suggests that yawning helps to heighten alertness.
Interesting Fact: Yawning might serve as a territorial display, a natural reflex designed to make the body appear larger by extending the arms and opening the mouth wide. When an animal yawns, humans instinctively notice the creature’s teeth and assess its potential for aggression or combat.
