A fascinating article: The 4 Stages of Fear, Attacked-by-a-Mountain-Lion Edition
In the throes of intense fear, we suddenly find ourselves operating in a different and unexpected way. The psychological tools that we normally use to navigate the world—reasoning and planning before we act—get progressively shut down. In the grip of the brain’s subconscious fear centers, we behave in ways that to our rational mind seem nonsensical or worse. We might respond automatically, with preprogrammed motor routines, or simply melt down. We lose control.
In this unfamiliar realm, it can seem like we’re in the grip of utter chaos. But although the preconscious fear centers of the brain are not capable of deliberation and reason, they do have their own logic, a simplified suite of responses keyed to the nature of the threat at hand. There is a structure to panic.
When the danger is far away, or at least not immediately imminent, the instinct is to freeze. When danger is approaching, the impulse is to run away. When escape is impossible, the response is to fight back. And when struggling is futile, the animal will become immobilized in the grip of fright. Although it doesn’t slide quite as smoothly off the tongue, a more accurate description than “fight or flight” would be “fight, freeze, flight, or fright”—or, for short, “the four fs.”
The article is somewhat longish, detailing the woman's reaction and eventual escape from the mountain lion. Here's part of her first reaction:
Just then she heard a rustling and looked up. At the top of the bank, not 30 feet away, stood a mountain lion. Tawny against the brown leaves of the riverbank brush, the animal was almost perfectly camouflaged. It stared down at her, motionless.
She stood stock-still.
Yellowtail had entered the first instinctual fear-response state, the condition of freezing known as attentive immobility. Even before she was aware of danger, subconscious regions of her brain were assessing the threat. Cued to the presence of a novel stimulus, the brain deployed the orienting reflex, a cousin of the startle reflex. Within milliseconds Yellowtail’s heart rate and breathing slowed. A brain region called the superior colliculus turned her head and slewed her eyes so that the densest part of the retina, the fovea, formed a detailed image of the cat. The visual information then flowed via the thalamus to the visual cortex and the amygdala, the key brain center for evaluating threat. Her pattern-recognition system found a match in the flow of sensory information. It recognized a pair of eyes, then the outline of a feline head. In less than half a second, before her cortex even had time to complete the match and recognize what she was seeing, her emotional circuitry had already assessed the situation: It was bad. Subconsciously, her brain also determined that the threat was not immediately pressing, and so a region called the ventral column of the periaqueductal gray (PAG) triggered attentive immobility. This is generally considered the first stage of the fear response, because it tends to occur when the threat is far away or not yet aware of the subject’s presence. The goal is to keep it that way.