Tingling palms and knocking knees: Why do we fear heights?

Kennywood – Pittsburgh’s premier amusement park – has filled my childhood with magical memories. Riding the stunning carousel horses around-and-around to the accompaniment of big band music. The scent of Potato Patch fries and funnel cake wafting through air. But what is the one memory I’ll never forget? The 251-foot Pitfall scaring the living daylights out of me.

The Pitfall at Kennywood Park

The Pitfall at Kennywood Park. Photo credit: Scott Jones

The Pitfall, now a retired ride, would leisurely take you 251 feet up into the sky and pause at the top so you could take in the view. With nothing more than a subtle *click* the brakes release and in a brief terrifying moment riders scream as they plummet towards earth.

One year during my 7th grade Kennywood school picnic, in a heroic effort I convinced some nervous friends that going on the Pitfall was the best idea ever. A few were crying actual tears in protest but ultimately we decided to ride. You’re only in 7th grade once, right?

We got in line and when our turn arrived a park employee locked us down in our seats, legs dangling below us. I had built the Pitfall up so much in my mind and I was confident about our decision to ride until we made it halfway up the ascent.

Halfway up. That’s where the whole idea turned sour. Turns out I have acrophobia – I’m deathly afraid of heights!

 Just looking at this picture makes my hands start to tingle!

The neurobiology of fear

Where does fear originate in our brain? Scientists believe that the brain region known as the amygdala plays an important role in triggering fear. Greek for ‘almond’, describing it’s shape, the amygdala sits in the medial temporal lobe of the brain.

The amygdala highlighted in orange.

The amygdala highlighted in orange.

A fear stimulus, such as heights, activates a cascade of events in the brain. The sensory cortex acknowledges something as frightening and signals the amygdala. In turn, the amygdala notifies the hypothalamus and the brainstem and you feel fear.

In humans, a very rare hereditary illness, Urbach-Wiethe disease, can cause bilateral symmetrical loss of all the cells in the amygdala. Without the amygdala the fear signaling cascade is broken and individuals are unable to experience fear. One famous patient, a 44-year-old woman known only as SM, exemplifies this fearlessness.

One night while walking home past a park, SM was grabbed by a man who put a knife to her throat, and exclaimed, “I’m going to cut you!”. Without feeling afraid she replied, “If you’re going to kill me, you’re gonna have to go through my God’s angels first.” Ballsy and effective. He responded by releasing her and she calmly walked back home. Extraordinarily, the following night she walked past the very same park again!

SMBrainScanMRI brain scan of SM compared to a healthy control subject.
The regions circled in red represent the amygdala and in SM is void of tissue.

Like others with Urbach-Wiethe disease, SM has characteristic bilateral amygdala lesions. SM’s IQ, memory, and language are normal. Although she experiences a wide range of other emotions, in her adult life there has never been an instance in which she has felt fear.  She appears to understand the concept of fear, having personally felt it once as a child, when she was cornered by a friend’s Doberman Pinscher. This incidence was presumably prior to loss of her amygdala. As an adult SM is able to recognize fear from body language and prosody of an individual’s voice, but interestingly she is unable to discern fear in static facial expressions.

In a study by Feinstein et al., SM was asked to participate in a number of frightening tasks. She was shown terrifying horror films, asked to hold large snakes and spiders, and taken to a haunted house. She never once showed signs of fear and when prompted described her experiences as feeling overwhelmingly “curious”.

SMFear(A) SM holding a snake,
(B) A spider SM tried to touch,
(C) Waverly Hills Sanatorium Haunted House SM toured

Self-described levels of fear following carbon dioxide inhalation.

Self-described levels of fear following carbon dioxide inhalation.

In a new study Feinstein and colleagues tried a different approach to induce fear and panic in SM and two other subjects with Urbach-Wiethe disease by exposing them to carbondioxide (CO2). Breathing in CO2 creates the sensation of suffocation and upon inhalation the subjects described feelings of being “overwhelmed by the panic and fear of dying”. It worked! SM felt fear for the first time in her adult life. But how?

The brainstem controls basic bodily functions such as breathing and heart rate. SM’s sensation of fear suggests that ultimately the brainstem, the endpoint for the fear cascade, holds the key to the conscious experience of fear. Specific threats, such as CO2, may bypass the circuit and impact the brainstem directly, eliciting fear without receiving a signal that has been processed through higher brain regions and the amygdala.

While scientists have not yet performed a field experiment with SM riding a Kennywood-escque Pitfall, Daniel Tranel, a professor of neurology and psychology at the University of Iowa, has been studying SM for years and tells NPR that SM reports being unafraid of heights. So unless she is sucking in CO2 on the ride, a simple roller coaster used as a fear stimulus that would be processed through the amygdala rather than directly impacting the brainstem, is unlikely to faze her.

Do we have an innate fear of heights?

Barring that you have an intact amygdala, are we programmed to fear heights from birth? Several studies have addressed this issue using a visual cliff.

Visual Cliff

A visual cliff is a trick-of-the-eye testing apparatus where an opaque patterned surface is connected to a transparent glass surface. Below the transparent side is a lower level that has the same pattern as the opaque surface. The visual cliff creates the illusion that you could fall over the edge.

Researchers noticed that if an infant was able to crawl and move on their own accord then they were also more wary of the “cliff”. However, if the child was “prelocomotor”, or younger than crawling age, they did not fear the edge. This is likely because as a baby learns to move around they also become aware of distances, depth perception, and begin coordinating their visual system with movement through their environment.

This experiment has been reproduced in a number of animal species including kittens that also utilize visual cues in movement. The visual cliff did not deter animals, such as rats, which predominately rely on tactile cues by whisking surfaces with their whiskers rather than vision to navigate their environment.

Thus it would seem as though fear of heights is a learned response to experiences, such as falling or near falling incidences, rather than something we are born with.

So what happened with the Pitfall after I realized that being more than 15 feet up in the air was too high for me? Well I survived. I actually rode the ride several more times since, rationalizing that the ride was engineered well and I was probably statistically safe.  If you ever get the chance to ride something like the Pitfall, try placing a dime on your knee to watch it levitate in front of you as you drop.  It might just keep your mind off of the heights.

Feinstein J.S., Adolphs R., Damasio A. & Tranel D. (2010). The human amygdala and the induction and experience of fear., Current biology : CB, PMID:

Feinstein J.S., Buzza C., Hurlemann R., Follmer R.L., Dahdaleh N.S., Coryell W.H., Welsh M.J., Tranel D. & Wemmie J.A. (2013). Fear and panic in humans with bilateral amygdala damage., Nature neuroscience, PMID:

Campos J.J., Bertenthal B.I. & Kermoian R. (1992). EARLY EXPERIENCE AND EMOTIONAL DEVELOPMENT: The Emergence of Wariness of Heights, Psychological Science, 3 (1) 61-64. DOI:



  1. It is very interesting to see how fear works. the crazy part is that a lot of people seek out fear to get away from problems and stress in there life or even just a huge adrenaline rush. But there are those people that just absolutely can not stand it and will do everything in there power not to get in a situation that is related to fear. I am one of those people that loves to seek out things that scare the crap out of me so i can get a huge adrenaline rush! I have found that its super addictive and it is kind of like a drug. Even though fear is negative a lot of times it has a positive affect in the long run, its like it is calming.

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