Human reflexes are controlled by the Autonomic Nervous System (ANS) – the lizard brain. It governs the involuntary actions of the body. When a stimulus occurs, a reflex response follows. For example, the body sweats when it is overheated, the pupils constrict in bright light, food processes through the digestive system, and the heart rate regulates all without a command. The startle reflex is also controlled by the ANS.
Humans are born with many reflexes. These are known as innate or inborn reflexes. Acquired reflexes evolve throughout life. However, the development of acquired reflexes actually begins at birth.[i] This process is called classical conditioning, or Pavlovian conditioning. Ivan Pavlov conducted early research on digestion and salivation using dogs in 1901, and discovered that dogs produced saliva before they ever got meat. He then designed an experiment to see if he could cause the dogs to produce saliva when he rang a bell.[ii]
In the experiment, the dogs received meat, which caused salivation, while a bell was rung at the same time. He repeated the pattern of bell-meat-saliva, bell-meat-saliva. Then, bell-no-meat, and they still produced the saliva. What happened was there was a pairing of the bell and producing saliva because of the meat. After repeated pairings, the lizard brain learned that after the bell, its job was to produce saliva – and it did! The stimulus (the bell) and the response (producing saliva) locked together because the lizard brain observed what was happening over and over, so it decided to automatically fire off the reflex because of the stimulus. For years scientists thought it was the association of the bell and the meat that caused the reflex to develop, but recent research has shown that it was the association of the bell and salivation.[iii]
Developing a reflex is a time sensitive process. To pick up this conditioned reflex response or acquired muscle reflex in humans, the critical timing is about half a second.[iv] For example, if a bell sound (stimulus) is followed by a poke half a second later, and this pairing is repeated, a flinch response may begin to occur after the bell alone, even in the absence of the poke. While the reflex can develop if the second stimulus occurs within two seconds, a half-second delay produces the strongest conditioned muscle reflex.
Typically, conditioned reflexes diminish when reinforcement stops. In the bell–meat–saliva example, if meat is no longer provided, salivation in response to the bell eventually ceases. Misophonia reflexes, however, do not extinguish in this way. This suggests that something about the trigger experience continues to strengthen the conditioned reflex. When a misophonia trigger occurs (such as a crunching sound), a reflex response follows. An accompanying emotional reaction intensifies the muscle response beyond the initial reflex. The ANS then associates the trigger with this heightened muscle tension, reinforcing the reflex. As a result, the misophonia reflex strengthens over time rather than diminishing.
[i] Goubet, Strasbauch, & Chesney, 2007; Rattaz, Goubet, & Bullinger, 2005
[ii] Pavlov, 2003
[iii] Donahoe & Vegas, 2004
[iv] Furedy & Riley, 1987