Matt Sikora doesn't look at the Rembrandts and Rodins at the Detroit Institute of Arts. His eyes are trained on the people looking at them.
Mr. Sikora watches where visitors stop, whether they talk or read, how much time they spend. He records his observations in a handheld computer, often viewing his subjects through the display cases or tiptoeing behind them to stay out of their line of sight. "Teenage daughter was with, but did not interact, sat on bench, then left," read his notes of one visit.