16.6 Issues with Virtual Preschool Engineering 303 of primitive musical instruments. Variations like this could be helpful but aren’t necessary for the world to serve its essential purpose. Note that one does not have true fluid dynamics in BlocksNBeadsWorld, but, it seems that the latter is not necessary to encompass the phenomena covered in cognitive developmental tests or preschool tasks. The tests and tasks that are done with fluids can instead be done with masses of beads. For example, consider the conservation of volume task shown in Figures 16.1 and 16.2 below: it’s easy enough to envision this being done with beads rather than milk. Even a few hundred beads is enough to be psychologically perceived as a mass rather than a set of discrete units, and to be manipulated and analyzed as such. And the simplification of not requiring fluid mechanics in one’s virtual world is immense. Next, one can implement equations via which the adhesion coefficients of a bead are deter- mined in part by the adhesion coefficients of nearby beads, or beads that are nearby in certain directions (with direction calculated in local spherical coordinates). This will allow for complex cracking and bending behaviors — not identical to those in the real world, but with similar qual- itative characteristics. For example, without this feature one could create paperlike substances that could be cut with scissors — but with this feature, one could go further and create woodlike substances that would crack when nails were hammered into them in certain ways, and so forth. Further refinements are certainly possible also. One could add multidimensional adhesion coefficients, allowing more complex sorts of substances. One could allow beads to vibrate at various frequencies, which would lead to all sorts of complex wave patterns in bead compounds. Etc. In each case, the question to be asked is: what important cognitive abilities are dramatically more easily learnable in the presence of the new