Berman, R., The Psychology of Tickling And Why It Makes Us Laugh. 2016: Big Think.
286
Stafford, T., Why all babies love peekaboo. 2014, BBC_Future.
287
Vrticka, P., J. M. Black, and A. L. Reiss, The neural basis of humour processing. Nat Rev Neurosci, 2013. 14 (12): p. 860–868.
288
Messinger, D.S., A. Fogel, and K. L. Dickson, All smiles are positive, but some smiles are more positive than others. Dev Psychol, 2001. 37 (5): p. 642–53.
