A hiccup, medically known as singultus, is a sudden, involuntary spasm of the diaphragm, the large muscle below the lungs that controls breathing. This spasm causes a sharp, unplanned intake of breath, which is immediately cut short by the rapid closing of the vocal cords. The characteristic “hic” sound is produced when the air strikes the suddenly closed glottis, the opening between the vocal cords.
The Definitive Answer on Contagion
Hiccups are not contagious in the medical sense. They are not caused by viruses, bacteria, or any other transmissible infectious agent that can pass between individuals, unlike a common cold or the flu. Hiccups are an internal, neurological event resulting from an irritated reflex arc within the body. This physiological mechanism is entirely self-contained and does not involve external transmission, meaning you cannot “catch” hiccups from someone else who is experiencing them.
The Physiological Mechanism of Hiccups
Hiccups occur because of an involuntary reflex arc involving several key nerves and muscles. The diaphragm, the primary muscle of respiration, contracts suddenly and erratically. This unexpected contraction pulls air into the lungs.
The reflex arc is triggered by irritation along the pathways of the vagus and phrenic nerves. The vagus nerve extends from the brainstem to the abdomen, and the phrenic nerve controls the diaphragm’s movement. Irritation along these pathways causes the diaphragm’s spasm.
Following the spasm, the air rushing into the lungs causes the glottis to snap shut. This abrupt closure of the vocal cords stops the inhalation and creates the audible “hic” sound.
Why People Believe Hiccups Are Contagious
The misconception that hiccups are contagious persists because of psychological and social factors. When a person observes someone else hiccuping, it can trigger a subconscious focus on their own breathing and bodily functions. This heightened awareness can lead to an actual hiccup, which feels like a form of mimicry.
This phenomenon aligns with the concept of suggestion, where the act of hearing or seeing the behavior primes the observer to potentially experience it themselves. The brain also contains mirror neurons, which fire both when a person performs an action and when they observe the same action in others. While mirror neurons play a role in contagious actions like yawning and laughter, the resulting hiccup is a coincidence of an internal reflex being triggered by external observation, not a true contagion.