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differed from the present study in that subjects were not

given differential cues to predict whether the noxious

stimulus would occur or not.

 Additionally, individual differences in heart rate

 responding during fear conditioning have been observed

 (Hare, 1972; Hodes, Cook, and Lang, 1985). While most

 individuals responded to fear anticipation with

 predominantly heart rate acceleration, some individuals have

 been found to respond to anticipation of a feared stimulus

 with heart rate deceleration. As a consequence, it may be

 that a larger sample size is needed for a significant heart

 rate acceleration to be observed statistically.

 Skin conductance

 The predictions that SCR would be greater during shock

compared to the shock control trials were supported.

Consistent with previous literature, skin conductance

responses were greater during the threat of shock compared

to safe trials (Bankart & Elliot, 1974; Bowers, 1971a,

1971b). As expected, SCR also habituated during the shock

conditions, such that SCR during block 1 was significantly

greater than during blocks 2, 3, and 4.

Facial electromyography

 Corrugator EMG was expected to be greater during shock

compared to the no-shock condition, whereas zygomatic E-'.G

was expected to show a either a decrease or smaller increase

during the shock compared to the no-shock trials. Other