Experiments carried out on the ligand-binding curve of isolated human hemoglobin subunits yield a hyperbolic shape. What does this indicate about the behavior of hemoglobin molecules which show a sigmoidal ligand binding curve?

Experiments carried out on the ligand-binding curve of isolated human hemoglobin subunits yield a hyperbolic shape. What does this indicate about the behavior of hemoglobin molecules which show a sigmoidal ligand binding curve