Many studies suggest that tangibles and digital tabletops have potential to support collaborative interaction. However, previous findings show that users often work in parallel with such systems. One design strategy that may encourage collaboration rather than parallel use involves creating a system that responds to co-dependent access points in which more than one action is required to create a successful system response. To better understand how co-dependent access points support collaboration, we designed a comparative study with 12 young adults using the same application with a co-dependent and an independent access point design. We collected and analyzed categories of both verbal and behavioural data in the two conditions. Our results show support for the co-dependent strategy and suggest ways that the co-dependent design can be used to support flexible collaboration on tangible tabletops for young adults.