What happens if you block someone from smiling?

Effects of Blocking Smiles

No observable effects were noted regarding surprise and sadness when blocking someone from smiling. However, the inability to mimic expressions in both the upper and lower parts of the face led to a decreased ability to recognize fear. Additionally, two separate studies indicated that inhibiting mimicry specifically in the lower face hampered the capacity to differentiate between genuine and fake smiles [56,57] (refer also to [51]).