Physicians sometimes tap patients’ knees with a small rubber mallet. Their name for the quick, automatic kicking of the leg that results is the patellar reflex, an involuntary and instantaneous response. A physiology textbook published just after the Civil War said: “Striking the tendon below the patella gives rise to a sudden extension of the leg.” The good news is that our legs don’t stay stuck out there like that. They retreat on their own, with no help from us.
What Are Knee-Jerk Reactions?
The rest of us call this immediate and unthinking reaction to an external stimulus a knee-jerk reaction
It’s what’s going on when we shiver with the cold, snatch our hands back when we accidentally touch something very hot, or our knee jerks involuntarily when tapped in the right place.
The elevated patellar reflex test is not a test of the knee
The automatic reflex is controlled by nerves in the spinal cord and is a key indicator of the health of our central nervous system. It’s called a deep-tendon reflex, one of our body’s uncontrolled responses.
The knee-jerk reaction is instantaneous, automatic, reflexive, and can’t be stopped
One of the reasons our leg kicks out so quickly is that our nervous system takes a shortcut. Instead of the signal going from the knee to the smart part of our brain and awaiting instructions, it goes straight from the knee to our dark inner recesses and back again–instantly. The part of the spine the signal goes to is what is commonly called our lizard brain.*
Lizard brains*
Lizards and other lower-order animals have very simple brains that were designed back in dinosaur days to deal with primitive urges. Humans have primitive drives, too. We all know our survival instinct calls for fight or flight when we’re in life-threatening situations. Our other primal needs are for:
- Oxygen
- Water
- Food
- Sleep
- Shelter
Reactions and responses are synonyms—for the most part
Reactions are triggered by our lizard brains. Reactions are emotional. As S.K. Ball, the Arkansas Philosopher, used to say immediately before flying into a fit of fury, “I ain’t got but one nerve left and you done got on it.” Reactions are instant and instinctive, made without any consideration of long-term outcomes. Because reactions are spontaneous, they often produce unintended consequences, those things we didn’t take the time to anticipate.
Responses are initiated by our prefrontal cortex, a much more complex and intricate area of our brains. Responses are rational ways of using our intelligence to consider long-term consequences for ourselves and others. Some people call the prefrontal cortex our personality center because it manages our memory, speech, thoughts, emotions, and decision-making. When we learn to do more responding and more reacting, we make better decisions.
When the context is social, the knee-jerk reaction is emotional
Yes, a knee-jerk reaction happens without thinking, but it’s more than just not thinking. It’s also reacting in a predictable way without hesitation. It’s what bears do when you poke them with sharp sticks.
Psychology Today says our lizard brains are “a complex group of brain structures responsible for the formation of memories and emotions related to survival such as anxiety, fear, and anger that originally switched on at breakneck speed to help our ancestors survive attacks from other tribes or wild animals.” Whew. The short version is “Our lizard brains are programmed for survival.”
Our lizard brains pump adrenaline into our systems
Our hearts pound, taking over from our rational selves, like the time in college housing when we investigated the source of the terrified screams we had just heard and involuntarily jumped back when we lifted the toilet lid and found a large dead rat floating in the bowl. It had come up from the sewer through bends in the pipes designed to prevent such things from happening and trapped itself under a lid it couldn’t push up to escape from the slippery-sided ceramic toilet bowl filled with water. Acme Rat Control’s Mike Sherman told us it had exhausted itself trying to escape and finally drowned when its strength was gone.
Voluntary, involuntary, and reflex actions**
- Voluntary actions are generated internally, not by external stimuli. They involve conscious thought, which takes a bit of time.
- Involuntary actions are those that happen without our brain getting involved. Breathing is involuntary. We do not force ourselves to inhale or exhale. It takes care of itself with no intervention from us. Snatching our hand back when we get burned is another involuntary action.
- Reflex actions are initiated by the spinal cord. They are involuntary and they are carried out immediately. So kindly Old Doc Martin isn’t testing our knees, he’s checking the overall health of our nervous systems.
Knee-jerk reactions are emotional responses to things that happen outside ourselves
Adults with knee-jerk reactions are responding blindly and instantly instead of thinking about alternative courses of action before responding. Knee-jerk actions are closely related to el toro’s reaction when el matador taunts him with his capa roja.
Those who make knee-jerk reactions make worse decisions than those who don’t
What may have been the right decision once does not automatically mean it will be again. Know this: the only ones who never change their opinions are either foolish or dead. Abraham Lincoln, speaking of coming into possession of new facts, said “As our case is new, so we must think anew and act anew.”
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* As is nearly always the case, there are those who disagree with what’s commonly held to be true. It used to be said that the first human brains were only lizard brains, and as we evolved, we added bits and pieces that performed higher and higher functions. BBC Science Focus says this lizard brain thing is a lot of hooey. But that’s for people who study the evolution of brains. Our interest is in understanding how our knee-jerk responses cause us to make bad decisions.
** Regular readers readily recognize how reactions and responses are related to Daniel Kahneman’s System 1 and System 2 Thinking.
Bonus
The equivalent of our Gila monster/iguana/skink/anole brain sits at the bottom of Abraham Maslow’s Hierarchy of Needs. He was interested in how we develop socially, but he knew we first had to take care of our physiological needs. Many years after Abe built his pyramid, he added an even higher state than self–actualization, calling it self-transcendence.
“Transcendence refers to the very highest levels of human consciousness, behaving and relating to significant others, to human beings in general, to other species, to nature, and to the cosmos. – Abraham Maslow
