1. Developmental Robotics
2. Understanding Intelligence
3. Playground experiment:https://www.youtube.com/watch?v=uAoNzHjzzys
4. Video of passive dynamic walker robot of Tad McGeer:https://www.youtube.com/watch?v=WOPED7I5Lac
5. Video of a replication of passive dynamic walker:https://www.youtube.com/watch?v=rhu2xNIpgDE