“…Physiological measures: Use of instruments that provide information on physiological functions in order to gain greater awareness of internal states of a user. The processes can include brainwaves (Hinterberger, 2011 ; Choo and May, 2014 ; Prpa et al, 2015 , 2016 ; Amores et al, 2016 ; Kosunen et al, 2016 ; Du Plessis, 2017 ; Gu and Frasson, 2017 ), skin temperature and conductance (Shaw et al, 2007 ; Hinterberger, 2011 ; Gromala et al, 2015 ; Bernal and Maes, 2017 ; Du Plessis, 2017 ), respiration (Davies and Harrison, 1996 ; Shaw et al, 2007 ; Hinterberger, 2011 ; Vidyarthi, 2012 ; Bal, 2013 ; Kitson et al, 2014 ; Prpa et al, 2015 , 2016 , 2017 ; Roo et al, 2016 ; van Rooij et al, 2016 ; Du Plessis, 2017 ; Patibanda et al, 2017 ), and heart rate and heart rate variability (Shaw et al, 2007 ; Hinterberger, 2011 ; Muñoz et al, 2016 ; Roo et al, 2016 ; Bernal and Maes, 2017 ; Chittaro et al, 2017 ).…”