Contingent Negative Variation : An Electric Sign of Sensori-Motor Association and Expectancy in the Human Brain Walter, W. Grey ; Cooper, R. ; Aldridge, V. J. ; McCallum, W. C. ; Winter, A. L. Abstract Publication: Nature Pub Date: July 1964 DOI: 10.1038/203380a0 Bibcode: 1964Natur.203..380W