Humans are Well Tuned to Detecting Agents Among Non-agents: Examining the Sensitivity of Human Perception to Behavioral Characteristics of Intentional Systems

Abstract

For efficient social interactions, humans have developed means to predict and understand others' behavior often with reference to intentions and desires. To infer others' intentions, however, one must assume that the other is an agent with a mind and mental states. With two experiments, this study examined if the human perceptual system is sensitive to detecting human agents, based on only subtle behavioral cues. Participants observed robots, which performed pointing gestures interchangeably to the left or right with one of their two arms. Onset times of the pointing movements could have been pre-programmed, human-controlled (Experiment 1), or modeled after a human behavior (Experiment 2). The task was to determine if the observed behavior was controlled by a human or by a computer program, without any information about what parameters of behavior this judgment should be based on. Results showed that participants were able to detect human behavior above chance in both experiments. Moreover, participants were asked to discriminate a letter (F/T) presented on the left or the right side of a screen. The letter could have been either validly cued by the robot (location that the robot pointed to coincided with the location of the letter) or invalidly cued (the robot pointed to the opposite location than the letter was presented). In this cueing task, target discrimination was better for the valid versus invalid conditions in Experiment 1 where a human face was presented centrally on a screen throughout the experiment. This effect was not significant in Experiment 2 where participants were exposed only to a robotic face. In sum, present results show that the human perceptual system is sensitive to subtleties of human behavior. Attending to where others attend, however, is modulated not only by adopting the Intentional Stance but also by the way participants interpret the observed stimuli.