“…Regarding the dialog system underlying the process of conversation, almost half of automated CAs ( n = 12) employed natural language processing and machine learning to carry on an interaction 8 , 9 , 12 , 27 , 30 , 31 , 34 , 38 , 39 , 41 , 43 , 45 . Predefined dialog or interactions assembled, and matched to the user input in a dynamic manner was used in 10 studies 10 , 11 , 26 , 28 , 29 , 32 , 33 , 35 , 40 , 44 , while 3 used a mixed dialog system 36 , 37 , 42 . These agents communicated through text ( n = 13) 10 , 12 , 26 , 28 – 30 , 32 , 35 , 37 , 40 , 42 – 44 , speech ( n = 2) 8 , 38 , and non-verbal cues ( n = 4) 9 , 34 , 41 , 45 , while multiple modalities communication was employed by 5 studies 11 , 31 , 33 , 36 , 39 .…”