Trusting Humans and Avatars: A Brain Imaging Study Based on Evolution Theory

Avatars, as virtual humans possessing realistic faces, are increasingly used for social and economic interaction on the Internet. Research has already determined that avatar-based communication may increase perceived interpersonal trust in anonymous online environments. Despite this trust-inducing potential of avatars, however, we hypothesize that in trust situations, people will perceive human faces differently than they will perceive avatar faces. this prediction is based on evolution theory, because throughout human history the majority of interaction among people has taken place in face-to-face settings. therefore, unlike perception of an avatar face, perception of a human face and the related trustworthiness discrimination abilities must be part of the genetic makeup of humans. Against this background, we conducted a functional magnetic resonance imaging experiment based on a multiround trust game to gain insight into the differences and similarities of interactions between humans versus human interaction with avatars. Our results indicate that (1) people are better able to predict the trustworthiness of humans than the trustworthiness of avatars; (2) decision making about whether or not to trust another actor activates the medial frontal cortex significantly more during interaction with humans, if compared to interaction with avatars; this brain area is of paramount importance for the prediction of other individuals’ thoughts and intentions (mentalizing), a notably important ability in trust situations; and (3) the trustworthiness learning rate is similar, whether interacting with humans or avatars. thus, the major implication of this study is that although interaction on the Internet may have benefits, the lack of real human faces in communication may serve to reduce these benefits, in turn leading to reduced levels of collaboration effectiveness.  agent, avatar, brain, cognitive neuroscience, evolutionary psychology, evolution theory, functional magnetic resonance imaging (fMRI), medial frontal cortex (MFC), mentalizing, NeuroIS, theory-of-mind (tOM). deteRMining who Can be tRusted and who Cannot has been crucial since the days of ancient civilizations. From the time of the emergence of early hominids such as Australopithecus afarensis, some 3.5 million years ago, until the recent past, trust in A BRAIN IMAgINg StuDy BASED ON EVOlutION thEORy 85 individuals who turned out not to be trustworthy could result in loss, or even death [21, 68]. thus, it is critical for humans to possess distinctive trustworthiness prediction abilities. Attention to another person’s face in a trust situation is of particular importance because the human face has been shown to allow one individual to predict another’s emotional state, intention, and behavior (e.g., [33, 57]). this predictive function has demonstrated application to trustworthiness [116, 121, 122]. thus, all other things being equal, the inability to see another person’s face creates more difficulty for predicting the other individual’s trustworthiness than there would be in a situation in which facial information is available. Biological anthropologists (e.g., [14, 20]) report that face-to-face interaction has been the main communication medium for more than 99 percent of human history (i.e., since the emergence of the first hominids). It follows, then, that application of Darwin’s theory of evolution [23] would suggest that the human trait of processing facial information, and the related prediction abilities, must be part of the genetic makeup of humans—a notion that is widely supported in the scientific literature . As direct support for these statements, scientific evidence shows that newborns react to human faces in the first hours of life [48]. Clearly, such behavior signifies that the ability to perceive individual faces is innate, and not learned. the intrinsic human preference toward face-to-face interaction suggests that individuals would not be predisposed to communicate through electronic methods (e.g., e-mail or text-based Internet chat). Evidence based on empirical research supports this view (see, e.g., the works reviewed in [59, 61]). the theoretical arguments underlying this idea, as well as the implications, are summarized under the media naturalness proposition [59], which Kock later refers to as the media naturalness hypothesis [60] and the media naturalness theory [61]. In essence, this theoretical framework defines the mismatch that exists between the characteristics of face-to-face interaction (which is the benchmark, due to its 100 percent naturalness) and the characteristics of other forms of communication (e.g., e-mail) as independent variables, whereas cognitive effort, communication ambiguity, and physiological arousal are defined as dependent variables. the degree of naturalness of a communication medium can be evaluated based on the degree to which it incorporates the characteristics of face-to-face interaction [59, 61]. the primary conditions for assessing the level of naturalness include (1) two communicating people share the same context, and they are able to see and hear each other, (2) individuals can quickly (i.e., in real time) exchange communicative stimuli, (3) the situation provides the ability to both convey and observe facial expressions, (4) to convey and observe body language, and (5) to convey and listen to speech. the 86 RIEDl, MOhR, KENNINg, DAVIS, AND hEEKEREN theory predicts that a decrease in the degree of naturalness (i.e., a higher degree of mismatch) results in three major effects regarding a communications process: (1) increased cognitive effort, (2) increased ambiguity, and (3) decreased physiological arousal (in terms of excitement). Importantly, a low degree of naturalness can negatively affect satisfaction, performance, and productivity in a number of collaborative tasks (e.g., customer support of an online service firm), although in computer-mediated environments humans also have the ability to compensate for lower degrees in naturalness—an ability known as compensatory adaptation (e.g., ). to date, both conceptual and empirical articles have investigated the relationship between face-to-face interaction and a number of communications media (see, e.g., research reviewed in [59, 61]). these investigations include e-mail, text-based Internet chat, as well as audioand videoconferencing. Despite the insights generated by the extensive number of articles investigating these more traditional communications media, our study adds significantly to the extant literature through our focus on the medium of avatars, which has gained considerable momentum in use over the past few years, but has not been explored in this regard in the literature. In human–computer interaction, the term avatar is used “as a label for digital representations of humans in online or virtual environments” [6, p. 64]. typically, avatars are virtual humans that possess realistic faces [29], a fact that is confirmed in several studies published in the IS literature (e.g., [25, 86, 112]). Among the many applications for avatars, both in practical function and as entertainment (e.g., virtual conferences [7], e-learning [34], shopping in virtual malls [73], instant messaging [43], and product innovation [66]), such characters are increasingly used for interactions among humans on the Internet [7, 82]. Against this background, avatars are a ubiquitous phenomenon in today’s computerized world, and are important in both private and organizational contexts (e.g., Second life, World of Warcraft). Because attention to a realistic portrayal of a human face is of particular importance for trust perceptions [117], it has been theorized that the use of avatars may positively affect trust perceptions in computer-mediated interactions, thereby mitigating uncertainty perceptions that are afforded by the anonymity of the Internet. In fact, previous research  found that avatar-based communication increases perceived interpersonal trust, relative to the more traditional communications media such as text chat, although an avatar’s face does not need to resemble a computer user’s real face because it can be chosen freely [87]. Importantly, technologies exist that capture a user’s facial expressions via a camera in order to transmit them in real time to the avatar’s face (e.g., [120]). thus, actual facial expressions are transmitted into the virtual world, blurring the boundaries between the real world and cyberspace. Despite the potential for avatars to induce trust through facial expression, however, evolution theory would suggest that a human face is perceived differently when compared to an avatar face [21, 23, 90, 121], and this is expected to hold true even in a static context (i.e., presentation of pictures of human or avatar faces rather than animations) (e.g., [77, 85, 116, 122]). For human faces, studies indicate that a judgment of reliable trustworthiness can be formed after an exposure time of 100 milliseconds (ms) [121], and because such times are not sufficient for saccadic eye movements, A BRAIN IMAgINg StuDy BASED ON EVOlutION thEORy 87 trustworthiness judgments are usually “single glance” impressions [116]. the automatic quality of processing trust judgments suggests that information-processing traits are hardwired (e.g., [59]),