Experimental manipulation of a unique cue in Pavlovian SCR conditioning with humans.

We report two experiments on positive and negative patterning in human skin conductance response (SCR) conditioning with a manipulable unique cue. In experiment 1 flashing red lights, arrayed horizontally, were used as elements and apparent movement was used as additional (unique) cue when the elements were presented in compound. Positive and negative patternings were both acquired readily, and positive patterning transferred to new stimuli (green lights, vertically arrayed). The unique cue did not influence these outcomes. Experiment 2 examined only positive patterning, using a more conventional unique cue, a visual frame that surrounded the letter stimuli on compound trials but not on element trials. The unique cue again facilitated neither acquisition nor transfer. These results do not support either the unique cue extension of the Rescorla-Wagner theory or configural theories. Human participants seem to utilize 'size' or 'number' or some other abstract feature in preference to available concrete stimuli.