“…Based on existing literature, there is a lack of consensus regarding the definitions of conversational agents, dialogue systems, embodied conversational agents, smart conversational interfaces, or chatbots 1 , 8 , 9 , 12 , 13 . Examples of conversational agents include (but are not limited to): chatbots, which have the ability to engage in “small talk” and casual conversation; embodied conversational agents, which involve a computer-generated character (eg avatar, virtual agent) simulating face-to-face conversation with verbal and nonverbal behavior; and smart conversational interfaces such as Apple Siri, Google Now, Microsoft Cortana, or Amazon Alexa 1 , 8 , 9 . For the purposes of this review, we considered the subset of conversational agents that use any unconstrained natural language input.…”