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The effects of electrodermal lability and stimulus significance on the amplitude of the skin conductance response (SCR) component of the orienting response (OR) to stimulus change were examined. Subjects were pre-selected in terms of the frequency of nonspecific responses (NSRs) displayed during a period of no stimulation. In Experiment 1 (N=56), high and low NSR male subjects received 12 presentations of a 5-sec, 1000 Hz tone followed by a test trial on which tone frequency was 500 Hz. Half of the subjects in each NSR group were required to perform a reaction time (RT) response to stimulus offset. Although high NSR groups and RT groups displayed larger test-trial responses than low NSR and no-RT groups respectively, stimulus change alone was sufficient to produce an increase in SCR amplitude. In Experiment 2 (N=40), high and low NSR male subjects received 12 visually-presented female names, and on trial 13, half the subjects in each NSR group received their own name, while the other half received a neutral male name. High NSR groups and own-name groups displayed larger test-trial responses than low NSR groups and neutral-name groups respectively. However, stimulus change alone was sufficient to produce an increase in SCR amplitude in the high NSR group. The results are interpreted as indicating that stimulus change alone is sufficient to produce an increase in OR amplitude, and that the relationship between stimulus change and stimulus significance is additive rather than multiplicative. [ABSTRACT FROM AUTHOR]