Pupillometric signs of brain activation vary with level of cognitive processing

Science  17 Mar 1978:
Vol. 199, Issue 4334, pp. 1216-1218
DOI: 10.1126/science.628837


The idea that hierarchically higher brain processes require greater amounts of central nervous system vigilance or activation for their execution was tested in two experiments measuring pupillary dilation during the decision interval of a hierarchically structured letter-matching task. Larger dilations indicative of increased activation were observed for letter pairs requiring higher levels of processing.