Table 2.

A summary of the annotation schema categories used.

Category	Description
Title	The title of the research paper or article
Year	Publication Year
Scenario	A description of the human-robot scenario used in the article
Application	What is the main application domain presented in the article
Robot	Type of robot(s) presented in the article
Role	The main role of the robot/agent with in the scenario presented
Definition	The definition of “engagement” presented in the context of the article
Affect	Is there an affective component to the engagement definition
Participants' type	Are the participants of the study children, adults or both
Number of participants	Indicates the number of participants included in any study (or studies) presented in the article
Lab study	Did the article include a study that is conducted in a laboratory settings
Sensors used perception/how?	What sensors are used to measure engagement (if any)
Perception	Is sensory information used for training an ML model?
Research objectives	What are the aims (purpose), research questions and/or hypotheses presented in the article
Engagement type	Is the article focusing on the perception, generation or simulation of engagement
Study attributes	What are the main evaluated attributes presented in the article
Scenario tag	In what context is the interaction taking place?
Finding/s	The main finding presented in the article
Mode	Was the operating mode of the robotic agent automated or based on a Wizard-Of-Oz approach?
Language	What language was the study conducted in?
Country	Where was the study conducted?
Perception	How is participant perception measured?
measurements	Questionnaires/video analysis/observation
Mode of use	Was the technical setting conducted in real-time, simulated or crowd sourced
Type of paper	What is the main type of the article presented (e.g., Technology, User evaluations etc.)