<P> People with acrophobia can experience a panic attack in high places and become too agitated to get themselves down safely . Approximately 2--5% of the general population has acrophobia, with twice as many women affected as men . The term is from the Greek: ἄκρον, ákron, meaning "peak, summit, edge" and φόβος, phóbos, "fear". </P> <P> Traditionally, acrophobia has been attributed, like other phobias, to conditioning or a traumatic experience . Recent studies have cast doubt on this explanation; a fear of falling, along with a fear of loud noises, is one of the most commonly suggested inborn or "non-associative" fears . The newer non-association theory is that a fear of heights is an evolved adaptation to a world where falls posed a significant danger . The degree of fear varies and the term phobia is reserved for those at the extreme end of the spectrum . Researchers have argued that a fear of heights is an instinct found in many mammals, including domestic animals and humans . Experiments using visual cliffs have shown human infants and toddlers, as well as other animals of various ages, to be reluctant in venturing onto a glass floor with a view of a few meters of apparent fall - space below it . While an innate cautiousness around heights is helpful for survival, an extreme fear can interfere with the activities of everyday life, such as standing on a ladder or chair, or even walking up a flight of stairs . </P> <P> A possible contributing factor is a dysfunction in maintaining balance . In this case the anxiety is both well founded and secondary . The human balance system integrates proprioceptive, vestibular and nearby visual cues to reckon position and motion . As height increases, visual cues recede and balance becomes poorer even in normal people . However, most people respond by shifting to more reliance on the proprioceptive and vestibular branches of the equilibrium system . </P> <P> An acrophobic, however, continues to over-rely on visual signals whether because of inadequate vestibular function or incorrect strategy . Locomotion at a high elevation requires more than normal visual processing . The visual cortex becomes overloaded resulting in confusion . Some proponents of the alternative view of acrophobia warn that it may be ill - advised to encourage acrophobics to expose themselves to height without first resolving the vestibular issues . Research is underway at several clinics . </P>

Where does a fear of heights come from