# Social Responses to Virtual Humans: The Effect of Human-Like Characteristics
## 1 Introduction
### How Humans Respond Socially to Virtual Humans  
Three early theories attempted to understand the social response to virtual humans. [PERSON] and [PERSON] (2016) claimed that the social response was due to the novelty of the situation and would disappear once the person became knowledgeable about the interaction and technology. More elaborate models include the aforementioned computer-as-social-actors by [PERSON] and his colleagues (1999, 2000, 2001) and the threshold model of social influence by [PERSON] et al. (2017) (for a complete review see (2018)). The essence of [PERSON] claim is that people unconsciously respond socially to computers, which was supported with ample empirical data of participants' categorical denial that they did not think there were programmers behind computers.  
[PERSON] et al. (2017), in their Threshold Model of Social Influence, claim that a social response is a function of two factors: perception of agency and behavior realism. Agency is high when the human knows that the virtual human is a representation of a human being; that is, in a form of an avatar. Conversely, the agency is low when the human knows that the virtual human is a representation of a computer program. Both are on continuous dimensions, from low behavioral realism and low agency (agent) to high behavioral realism and high agency (avatar). When the two factors are crossed and the threshold is met, social responses are evoked. This means that when the agency is high, behavioral realism does not necessarily have to be high to elicit social responses and vice versa.  
[PERSON], [PERSON], [PERSON] and [PERSON] (2018) took the agent-avatar paradigm further and varied the participant's belief (avatar versus agent) and varied the dynamic listening behavior (realism) of the virtual human on a self-disclosure task. They found that higher behavior realism, which was manipulated as providing or not providing feedback after the disclosure, affected the evaluation of the virtual human whereas the belief did not. This finding may deny the effect of agency (agent versus avatar) in [PERSON]'s theory but supports [PERSON] speculation that the more computers present human-like characteristics, the more likely they will elicit social behavior (2018) (p. 97). Similar findings were reported with robots (2018).  
[PERSON] et al. (2018) claimed that the reason studies had inconsistent results is because social responses are moderated with the level of immersion (desktop vs. fully immersive), dependent variable type (subjective vs. objective), task type (competitive vs. cooperative vs. neutral), and the control of the representation (human vs. computer).  
Indeed, the presence and strength of social response seem to be contingent on the nature of task and how it was measured. Given that there are so many applications and tasks a virtual human can do, it may be difficult to find a main effect on the strength of social responses applicable to all domains. One way to approach the problem is to focus on the mere presence of a virtual human and the additive effect of the human-like characteristics and simultaneously minimize the interaction with the virtual human. This may sacrifice the ecological validity of the findings, but would provide clarity in understanding the cognitive mechanics of social responses and provide a useful research framework for future investigation with more complex interactions and tasks.