non-newtonian liquid

Today my son and I tried SEED's science experiment "Viscosity: Is it Liquid or Solid?". It was ooey, gooey fun!  First we measured the water (1 cup) and added dye to it.  He wanted pink, so we turned it pink.  Then we measured the cornstarch (2 cups) and dumped it into the water. It looked like a normal mixture of powder and liquid. So far, so good.  But then I tried to stir it...