In everyday speech, freezing is often confused with tonic immobility, but they are not the same — tonic immobility is more extreme. Collapsed immobility, another extreme response, involves a sudden drop in heart rate and blood pressure, resulting in limp muscles, unlike the rigid muscles in tonic immobility. Victims typically faint or collapse and take time to recover due to a lack of oxygen in the brain. Hopper once dealt with a case where a man attempted to force a victim to perform oral sex, but she was unable to keep her head up. “She mentioned that her neck muscles were completely limp and her head moved around uncontrollably,” he explained. Victims might describe the experience as feeling dizzy, faint, or sleepy. Some describe it as “blacking out,” which can cause improperly trained investigators to assume the victim consumed excessive alcohol.
Freezing usually occurs early in an attack, while extreme responses tend to occur later, although they can happen in any order. Shifts between these behaviors can happen within milliseconds. Additionally, some individuals threatened with rape may make decisions, such as complying, because they believe it will help them avoid death or severe physical harm. Others may choose to fight or flee, while some may not experience a trauma response at all. However, all these responses can markedly affect a person’s consciousness and memory.
Neuroscientists often discuss the brain in terms of circuitries, which are networks of connected areas responsible for specific functions. The defense circuitry is extensively studied and operates similarly in all mammals: when a threat is detected, the defense circuitry can rapidly overwhelm brain functioning, greatly impacting thinking, behavior, and memory. It takes approximately three seconds for the defense circuitry to flood the prefrontal cortex with stress chemicals, significantly impairing it. As a result, our ability to reason diminishes, our language centers are affected, our attention shifts, and our memory encoding is altered.
Amy Arnsten, a neuroscientist at Yale University, is a prominent researcher on how stress impairs the prefrontal cortex. In a study conducted last year, her team discovered that exposure to even mild but uncontrollable stress quickly impairs the prefrontal cortex in both humans and animals. “Under stress, your brain disconnects from its more recently developed circuits and reinforces many of the primitive circuits, allowing unconscious reflexes that have been present for centuries to kick in,” she explained during our phone conversation.
Arnsten shared an experience from years ago, when she was walking through the woods in Vermont and a bear fell from a tree. Without thinking, she froze. The bear looked at her but didn’t see her. “It’s purely reflexive,” she noted. “Most animals perceive movement rather than detail, so freezing — particularly if escape is impossible — has been advantageous for survival throughout history.” However, freezing and tonic immobility evolved as defense mechanisms against animal predators, not human ones. Human predators do not always lose interest if their victim appears lifeless.