Direction of human motor responses by men and women to aversive stimulation

The frequency of extensions and flexions of the arms of 12 men and 12 women (ages 20-30 years) responding to a neutral tone or to an electric shock wa s recorded. Subjects had to choose between pushing or pulling a lever upon receipt of an acoustic signal which was paired or unpaired with an electric shock. They were instructed to perform either long duration movements, all owing for on-line control of the execution, ol short duration movements wit h prior specification of amplitude. Regardless of duration of movements, th e aversive signal increased the frequency of extensions and intraindividual variability of choices of the men bur decreased the frequency of extension s and intraindividual variability of choices of the women. These findings s how that stimuli such as pain or fear automatically elicit patterns of term inal motor states corresponding to Eight or flight, initiating processes of preparation of spatially oriented movements which are automatic and sex-ty ped and impair the use of the terminal cues for simultaneous preprogrammed voluntary movements.