Table 2.
Characteristics of the conversational agents evaluated in the included studies.
| Author, Year | Type of Communication Technology; Type of Conversational Agent | AI Methods Used | Dialogue Management | Dialogue Initiative | Input | Output | Task-Oriented |
|---|---|---|---|---|---|---|---|
| Azzini et al., 2003 | Smartphone and web-based; spoken dialog system. | Speech recognition and spoken dialog system. | Finite-state | Mixed | Spoken | Spoken, written | Yes |
| Baptista et al., 2020 | Smartphone app; ECA. | Speech recognition, natural language processing. | Finite-state | System | Spoken, visual | Spoken, written, visual | Yes |
| Beaudry et al., 2019 | Text messaging platform; chatbot. | Machine learning, NLU, NLP, deep learning, speech recognition. | Finite-state | System | Written | Written | Yes |
| Bickmore et al., 2010 | Framework; ECA. | Speech recognition, synthetic voice. | Finite-state | System | Spoken, visual | Spoken, written, visual | Yes |
| Bickmore et al., 2010 | Home desktop software; animated agent and interaction dialogues. | Not reported. | Finite-state | System | Visual | Spoken, visual | Yes |
| Bott et al., 2019 | Platform; ECA. | Text-to-speech, NLU. | Frame-based | Mixed | Spoken, visual | Spoken, written, visual | Yes |
| Chaix et al., 2019 | Smartphone and web-based; chatbot. | Machine learning, NLP. | Finite-state | System | Written, visual | Written | Yes |
| Dworkin et al., 2018 | Smartphone app; Avatar-based embodied agent. | Not reported. | Finite-state | Mixed | Spoken, written, visual | Spoken, written, visual | Yes |
| Easton et al., 2019 | Web-based; avatar and chatbot. | NLP, speech recognition. | Frame-based | Mixed | Spoken, written | Spoken, written, visual | Yes |
| Greer et al., 2019 | Facebook messenger; chatbot. | Not reported. | Finite-state | System | Written | Written, visual | Yes |
| Hauser-Ulrich et al., 2019 | Smartphone app; chatbot. | Not reported. | Finite-state | System | Written | Written, visual | No |
| Inkster et al., 2018 | Smartphone app; chatbot. | Machine learning, unsupervised learning. | Finite-state | System | Written | Written, visual | Yes |
| Lobo et al., 2017 | Android app; chatbot. | Speech recognition, speech synthesis, spoken natural language, hidden Markov model, natural language Understanding, natural language dialogue system. |
Frame-based | Mixed | Spoken, written | Spoken, written | Yes |
| Neerincx et al., 2019 | Platform independent app, robot and avatar. | Machine learning, deep learning, speech recognition, speech synthesis. | Finite-state | System | Visual | Spoken, written, visual | Yes |
| Rehman et al., 2020 | Android app; chatbot. | NLU, speech recognition, text to speech synthesis, neural network algorithm, machine learning, natural language processing, deep learning, spoken dialog. | Frame-based | User | Spoken, written | Spoken, written | Yes |
| Stephens et al., 2019 | SMS text messaging; chatbot. | Not reported. | Frame-based | Mixed | Written | Written | Yes |
| O’Hara et al., 2008 | Personal Digital Assistants (PDAs). | Not reported. | Finite-state | System | Written | Written | Yes |
| Philip et al., 2017 | Home desktop software; Virtual human ECA. |
Speech recognition, synthetic voice. |
Finite-state | System | Spoken | Spoken | Yes |
| Piau et al., 2019 | Semi-automated smartphone messaging system; chatbot. |
Speech to text. | Finite-state | System | Written | Written | Yes |
| Puskar et al., 2011 | Home desktop software; Relational Agent. | NLU, facial recognition, speech dialogue system. |
Frame-based | System | Written | Written | Yes |
| Richards and Caldwell, 2018 | Website; Avatar and Empathic ECA a. | Speech to text. | Finite-state | System | Visual | Written; spoken | No |
| Ryu et al., 2020 | Smartphone app; chatbot. | Speech recognition. | Frame-based | System | Visual | Written | No |
| Schroeder et al., 2018 | Smartphone app; chatbot. | Not reported. | Finite-state | System | Visual | Written | Yes |
| Sebastian & Richards, 2017 | Platform independent app; ECA. | Not reported. | Finite-state | System | Visual | Written | Yes |
| Shamekhi & Bickmore, 2018 | Home desktop software; an animated agent with spoken dialogue and sensing. | Spoken dialog system. | Frame-based | System | Respiration sensor | Spoken | Yes |
| Tielman et al., 2017 | Home desktop software; an animated agent with spoken dialogue. | Spoken dialog system. | Finite-state | System | Visual | Spoken; written | Yes |
Abbreviations: app: application; ECA: Embodied Conversational Agent; a Empathic ECA: empathic agent that provides face-to-face conversation in an empathic and caring way, to act as a virtual doctor for the family to interact with.