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Literature Study GuidesGirl InterruptedVelocity Vs Viscosity Summary

Girl, Interrupted | Study Guide

Susanna Kaysen

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Girl, Interrupted | Velocity vs. Viscosity | Summary



Susanna classifies the effects of insanity into two categories: slow and fast. Either the patient's thought processes slow down to a crawl or they speed up to a race. Viscosity slows down time, dulls sensory perception, and even causes the patient's heart rate to slow down. Any decision seems overwhelming, and the patient stays still.

Velocity, on the other hand, speeds up thought processes. A single thought invites a cascade of other thoughts and questions that spiral out of control. Moving from one idea to the next in seemingly free association, the patient becomes overwhelmed by a myriad of sharp sensory perceptions, images, and memories that interfere with making even the simplest decision.

While a patient might suffer from one or the other of these two vastly different states, outside observers cannot tell the difference, as both personality types are unable to act. Whether afflicted with viscosity or velocity, the result is the same: the patient is mentally paralyzed. Repetitive thoughts are a symptom of both types of insanity. One negative thought will trigger a familiar series of other negative thoughts, like a flu that always cycles through the same series of symptoms. Susanna's depression subjects her to both velocity and viscosity, "overload" and "underload," and she cannot control which state she will experience at any given time.


Classification is one of the most important tools of science. When Susanna classifies her experience of madness into two groups: velocity and viscosity (scientific terms borrowed from physics), she makes her inner turmoil tangible. During viscosity, she feels stuck in slow motion, as if she is moving through molasses. During velocity, she feels as if her life is in fast-forward mode, her mind constantly pulled in many directions to which a single thought might lead. While classification is a first step to understanding a phenomenon, understanding her predicament does not help Susanna to conquer it. She cannot control whether velocity or viscosity hits her any more than she can control the succession of self-destructive thoughts that invade her mind. Despite her astute observations, she is a prisoner of her emotions; both states render her immobile.

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