คำอธิบายSketch of a loose string paradigm apparatus.png
English: Fig 1. from scientific article titled Partner Choice in Raven (Corvus corax) Cooperation, by Kenji Asakawa-Haas, Martina Schiestl, Thomas Bugnyar, Jorg J. M. Massen
The small board could move along the tracks if the strings were simultaneously pulled. If only one subject pulled or if both subjects pulled asynchronously, the string was pulled through the ringbolts without affecting the small board.