Junpeng and co-workers have used our “tension trapping” strategy to follow the competition between symmetry-allowed disrotatory and symmetry-forbidden conrotatory ring closing starting on the dividing surface of the disrotatory pathway. The observe around 5% of symmetry-forbidden process, and the experimental findings are reproduced in molecular dynamics simulations. The paper has just been accepted for publication in J. Org. Chem. as part of a special issue in honor of the 50th anniversary of the Woodward-Hoffman rules.