Paralysis Common among Victims of Sexual Assault: 'Tonic Immobility' during Rape Is Thought to Have Evolved as a Survival Mechanism. (Involuntary Response)

Article excerpt

RENO, NEV. -- A large proportion of sexual assault victims experience an involuntary paralysis during the assault, according to several studies presented at the annual meeting of the Association for Advancement of Behavior Therapy.

The studies have important implications for the treatment of sexual assault victims in both the medical and legal arenas.

In one study, led by Brian P. Marx, Ph.D., of Temple University Philadelphia, and Jennifer M. Heidt, a graduate student, 88% of the victims of childhood sexual assault and 75% of the victims of adult sexual assault reported moderate or high levels of paralysis during the assault. The study included 89 women (45 undergraduates and 44 psychiatric inpatients) who reported experiencing sexual assault as a child and/or as an adult.

In another study, led by John P. Forsyth, Ph.D., of the University at Albany (N.Y.) and Tiffany K. Fuse, a graduate student, 66% of 147 sexual assault victims (all female undergraduates) reported some degree of paralysis during the assault.

The investigators, who are working together as part of one larger project led by Dr. Forsyth and Dr. Marx, compare rape-induced paralysis to a behavior widely studied in prey animals. Referred to as "tonic immobility," it is thought to have evolved as a survival mechanism.

"Predators are particularly sensitive to the actions of their prey," Ms. Heidt said in an interview. "Motionless prey represents dead prey. A predator is not going to be interested in dead prey."

The investigators used a 12-item dimensional subscale of the newly designed tonic immobility scale, a 44-item self-report questionnaire that they are working to validate. The scale assesses a number of aspects of the phenomenon, including feelings of paralysis, the inability to move, the inability to call out or scream, feeling cold, feelings of impending death, and feelings of detachment from oneself.

The study by Ms. …