The startle response, the almost instantaneous protective action following a sudden loud noise or other stimulus, is present in many animals. It has evolutionary value in that it enables escape from unanticipated dangers such as the sudden appearance of a predator. In humans, its purpose seems to be to make us look slightly silly when a car backfires.
Like other reflexes, the startle response is involuntary. To minimise response time it follows an abbreviated neural pathway emanating from the brainstem. Sometimes, neurological abnormalities disrupt this pathway leading to some bizarre outcomes.
Hyperekplexia is characterised by an exaggerated startle reflex resulting in a paralysing stiffening of the body. Sufferers are sometimes injured from falls. Fainting goat syndrome is an unrelated disorder but with similar outcomes.
The Jumping Frenchmen of Maine refers to another abnormal response to the startle reflex. Instead of paralysis, sufferers become highly suggestible. First noticed in lumber camps in northern Maine in the late nineteenth century, there remains some doubt as to whether it has neurological or psychological causes. For a few seconds after being startled, sufferers will obey commands to jump, throw objects or strike someone. Alternatively, they may involuntarily copy someone’s speech (echolalia) or actions (echopraxia).
Similar conditions occur in Indonesia and Malaysia (where it is called latah), northern Japan and other parts of Asia. Sufferers of latah fall into a trance-like state when startled and may display echolalia and echopraxia or may strike out or kick at those around them. An episode can last for as long as thirty minutes. Latah and related conditions are considered culture-bound syndromes as they are only observed in particular cultural settings.