Kismet: A Robot for Social Interactions with Humans

[picture of Kismet

An Exploration into Altricial Robotics

Kismet is an autonomous robot designed for social interactions with humans and is part of the larger Cog Project. In general, social robotics has concentrated on groups of robots performing behaviors such as flocking, foraging or dispersion, or on paired robot-robot interactions such as imitation. This project focuses not on robot-robot interactions, but rather on the construction of robots that engage in meaningful social exchanges with humans. By doing so, it is possible to have a socially sophisticated human assist the robot in acquiring more sophisticated communication skills and helping it learn the meaning these acts have for others. Our approach is inspired by the way infants learn to communicate with adults. Specifically, the mode of social interaction is that of a caretaker-infant dyad where a human acts as the caretaker for the robot.

An infant's emotions and drives play an important role in generating meaningful interactions with the caretaker. These interactions constitute learning episodes for new communication behaviors. In particular, the infant is strongly biased to learn communication skills that result in having the caretaker satisfy the infant's drives. The infant's emotional responses provide important cues which the caretaker uses to assess how to satiate the infant's drives, and how to carefully regulate the complexity of the interaction. The former is critical for the infant to learn how its actions influence the caretaker, and the later is critical for establishing and maintaining a suitable learning environment for the infant.

  • The Importance of Regulating Social Interactions

    An infant's motivations are vital to regulating social interactions with his mother. Soon after birth, an infant is able to display a wide variety of facial expressions, and responds to events in the world with expressive cues that his mother can read, interpret, and act upon. She interprets them as indicators of his internal state (how he feels and why), and modifies her actions to promote his well being. For example, when he appears content she tends to maintain the current level of interaction, but when he appears disinterested she intensifies or changes the interaction to try to re-engage him. In this manner, the infant can regulate the intensity of interaction with his mother by displaying appropriate emotive cues. The mother instinctively reads her infant's expressive signals and modifies her actions in an effort to maintain a level of interaction suitable for him.

    For Kismat, an important function for its motivational system is not only to establish appropriate interactions with the caretaker, but to also to regulate their intensity so that Kismet is neither over-whelmed nor under-stimulated by them. When designed properly, the intensity of Kismet's expressions provide appropriate cues for the caretaker to increase the intensity of the interaction, tone it down, or maintain it at the current level. By doing so, both parties can modify their own behavior and the behavior of the other to maintain the intensity of interaction that Kismet requires to behave adeptly.

  • En Route to Learning in a Social Context

    The use of emotional expressions and gestures facilitates and biases learning during social exchanges. Parents take an active role in shaping and guiding how and what infants learn by means of scaffolding. As the word implies, the parent provides a supportive framework for the infant by manipulating the infant's interactions with the environment to foster novel abilities. Commonly, scaffolding involves reducing distractions, marking the task's critical attributes, reducing the number of degrees of freedom in the target task, providing ongoing reinforcement through expressive displays of face and voice, and enabling the subject to experience the end or outcome of a sequence of activity before the infant is cognitively or physically able of seeking and attaining it for himself. The emotive cues the parent receives during social exchanges serve as feedback so the parent can adjust the nature and intensity of the structured learning episode to maintain a suitable learning environment where the infant is neither bored nor over-whelmed.

    In addition, during early interactions with his mother, an infant's motivations and emotional displays are critical in establishing the foundational context for learning episodes from which he can learn shared meanings of communicative acts. During early face-to-face exchanges with his mother, an infant displays a wide assortment of emotive cues such as coos, smiles, waves, and kicks. At such an early age, the infant's basic needs, emotions, and emotive expressions are among the few things his mother thinks they share in common. Consequently, she imparts a consistent meaning to her infant's expressive gestures and expressions, interpreting them as meaningful responses to her mothering and as indications of his internal state. Curiously, some experiments performed by developmental psychologists argue that the mother actually supplies most if not all the meaning to the exchange when the infant is so young. The infant does not know the significance his expressive acts have for his mother, nor how to use them to evoke specific responses from her. However, because the mother assumes her infant shares the same meanings for emotive acts, her consistency allows the infant to discover what sorts of activities on his part will get specific responses from her. Routine sequences of a predictable nature can be built up which serve as the basis of learning episodes. Furthermore, it provides a context of mutual expectations.

    For example, early cries of an infant elicit various care-giving responses from his mother depending upon how she initially interprets these cries and how the infant responds to her mothering acts. Over time, the infant and mother converge on specific meanings for different kinds of cries. Gradually the infant uses subtly different cries (i.e., cries of distress, cries for attention, cries of pain, cries of fear) to elicit different responses from his mother. The mother reinforces the shared meaning of the cries by responding in consistent ways to the subtle variations. Evidence of this phenomena exists where mother-infant pairs develop communication protocols different from those of other mother-infant pairs.

    An ongoing research goal is to implement these ideas so that Kismet is biased to learn how its actions influence the caretaker in order to satisfy its own drives. Toward this end, Kismet is endowed with a motivational system that works to maintain its drives within homeostatic bounds and motivates the robot to learn behaviors that satiate them. Further, Kismet can display a set of emotive expressions that are easily interpreted by a naive observer as analogues of the types of emotive expressions that human infants display. This allows the caretaker to observe Kismet's emotive expressions and interpret them as communicative acts. She assumes the robot is trying to tell her which of its needs must be tended to, and she acts accordingly. This establishes the requisite routine interactions for the robot to learn how its emotive acts influence the behavior of the caretaker, which ultimately serves to satiate the robot's own drives.

    The Robotic Platform

    [Kismet: May 1997] [Kismet: Sept 1997] [Kismet: Feb 1997] [Kismet: March 1998]

    To explore these ideas, Kismet was adapted from an existing active vision platform commonly used in the Cog Shop. The figure above shows various stages of development of Kismet. The original head is shown above at the far left (circa May 1997), and the current state of the robot is shown at the far right (circa March 1998). The appearance and degrees of freedom of the robot continues to evolve.

    Similar to other active vision systems, there are three degrees of freedom; each eye has an independent vertical axis of rotation (pan) and the eyes share a joint horizontal axis of rotation (tilt). Each eyeball has a color CCD camera embedded within it having a 5.6 mm focal length. Although this limits the field of view, most social interactions require a high acuity central area to capture the details of face-to-face interaction. However, infants have poor visual acuity which restricts their visual attention to about two feet away -- typically the distance to their mother's face when the infant is being held (for example, at one month the infant has a visual acuity between 20/400 to 20/600). This choice of camera is a balance between the need for high resolution and the need for a wide low-acuity field of view.

    [Kismet's facial expressions]

    Over time, the basic active vision platform has been embellished with facial features so that Kismet is capable of a wide range of emotive facial expressions (as shown in the figure above). Currently, these facial features include eyebrows (each with two degrees-of-freedom: lift and arch), ears (each with two degrees-of-freedom: lift and rotate), eyelids (each with one degree of freedom: open/close), and a mouth (with one degree of freedom: open/close). The robot is able to show expressions analogous to anger, fatigue, fear, disgust, excitement, happiness, interest, sadness, and surprise (shown in the figure below) which are easily interpreted by an untrained human observer.

    Planned extensions to kismet's sensor and motor systems include stereo microphones for auditory input as well as a synthesized articulatory model for vocalized outputs.

    Computational Hardware

    Kismet's active vision platform is attached to a parallel network of digital signal processors (Texas Instruments TMS320C40), as shown in the figure above. The DSP network serves as the sensory processing engine and implements the bulk of the robot's perception and attention systems. Each node in the network contains one processor with the option for more specialized hardware for capturing images, performing convolution quickly, or displaying images to a VGA display. Nodes may be connected with arbitrary bi-directional hardware connections, and distant nodes may communicate through virtual connections. Each camera is attached to its own frame grabber, which can transmit captured images to connected nodes.

    [Kismet's computational hardware]

    A pair of Motorola 68332-based microcontrollers are also connected to Kismet. One controller implements the motor system for driving the robot's facial motors. The second controller implements the motivational system (emotions and drives) and the behavior system. This node receives pre-processed perceptual information from the DSP network through a dual-ported RAM, and converts this information into a behavior-specific percept which is then fed into the rest of the behavior engine.

    The Software System

    [Behavior engine architecture]

    A framework for Kismet's behavior engine is shown to the right. The organization and operation of this framework is heavily influenced by concepts from psychology, ethology, and developmental psychology, as well as the applications of these fields to robotics as outlined in "Alternative Essenceses of Intelligence". The system architecture consists of five subsystems: the perception system, the motivation system, the attention system, the behavior system, and the motor system, an elaborated version from that presented in previous work, "A Motivational System for Regulating Human-Robot Interaction". The perception system extracts salient features from the world, the motivation system maintains internal state in the form of ``drives'' and ``emotions'', the attention system determines saliency based upon perception and motivation, the behavior system implements various types of behaviors as conceptualized by the theories of Tinbergen and Lorenz, and the motor system realizes these behaviors as facial expressions and other motor skills.

    Early Experiments in Regulating Social Interaction

    A series of experiments were performed with Kismet using a specific implementation of the behavior engine framework. The total system consists of three drives: fatigue, social, and stimulation; three consummatory behaviors: sleep, socialize, and play; two visually-based percepts: ``face'' and ``non-face''; five emotions: anger, disgust, fear, happiness, sadness; two expressive states: tiredness and interest, and their corresponding facial expressions.

    A more detailed schematic for the ``social'' circuit is shown below. The ``fatigue'' circuit and the ``stimulation'' circuit follow a similar structure. See "Infant-like Social Interactions Between a Robot and a Human Caretaker" for an in depth presentation.

    [social drive circuit]

    Each experiment involved a human interacting with Kismet either through direct face-to-face interaction, by waving a hand at the robot, or using a toy to play with the robot. Two toys were used: a small plush black and white cow and an orange plastic slinky. The perceptual system classifies these interactions into two classes: ``face stimuli'' and ``non-face stimuli''. The face detection routine classifies both the human face and the face of the plush cow as face stimuli, while the waving hand and the slinky are classified as non-face stimuli. Additionally, the motion generated by the object gives a rating of the stimulus intensity. The robot's facial expressions reflect its ongoing motivational state (i.e. it's mood) and provides the human with visual cues as to how to modify the interaction to keep the robot's drives within homeostatic ranges.

    In general, as long as all the robot's drives remain within their homeostatic ranges, the robot displays ``interest''. This cues the human that the interaction is of appropriate intensity. If the human engages the robot in face-to-face contact while its drives are within their homeostatic regime, the robot displays ``happiness''. However, once any drive leaves its homeostatic range, the robot's ``interest'' and/or ``happiness'' wane(s) as it grows increasingly distressed. As this occurs, the robot's expression reflects its distressed state. This visual cue tells the human that all is not well with the robot, whether the human should switch the type of stimulus, and whether the intensity of interaction should be intensified, diminished or maintained at its current level.

    For all of the experiments, data was recorded on-line in real-time during interactions between a human and the robot. The data plots below show the activation levels of the appropriate emotions, drives, behaviors, and percepts. Emotions are always plotted together with activation levels ranging from 0 to 2000. Percepts, behaviors, and drives are often plotted together. Percepts and behaviors have activation levels that also range from 0 to 2000, with higher values indicating stronger stimuli or higher potentiation respectively. Drives have activations ranging from -2000 (the over-whelmed extreme) to 2000 (the under-whelmed extreme).

  • Results from Regulating the Intensity of Face-to-Face Interaction

    [face-to-face interaction experiments]

    This plot shows how Kismet's internal state responds to varying intensities of face-to-face contact. Before the run begins, the robot is not shown any faces so that the social drive lies in the lonely regime and the robot displays an expression of ``sadness''. At t=10 the experimenter makes face-to-face contact with the robot. From 10 >= t >= 58 the face stimulus is within the desired intensity range. This corresponds to small head motions, much like those made when engaging a person in conversation. As a result, the social drive moves to the homeostatic regime, and a look of ``interest'' and ``happiness'' appear on the robot's face. From 60 >= t >= 90 the experimenter begins to sway back and forth in front of the robot. This corresponds to a face stimulus of over-whelming intensity, which forces the social drive into the asocial regime. As the drive intensifies toward a value of -1800, first a look of ``disgust'' appears on the robot's face, which grows in intensity and is eventually blended with ``anger''. From 90 >= t >= 115 the experimenter turns her face away so that it is not detected by the robot. This allows the drive to recover back to the homeostatic regime and a look of ``interest'' returns to the robot's face. From 115 >= t >= 135 the experimenter re-engages the robot in face-to-face interaction of acceptable intensity and the robot, and the robot responds with an expression of ``happiness''. From 135 >= t >= 170 the experimenter turns away from the robot, which causes the drive to return to the lonely regime and redisplay ``sadness''. For t >= 170 the experimenter re-engages the robot in face-to-face contact, which leaves the robot in an ``interested'' and ``happy'' state at the conclusion of the run.

    The results from the rest of the aforementioned experiments can be found in "Infant-like Social Interactions Between a Robot and a Human Caretaker". A sampling of video clips from similar experiments is available in the next section.

    Kismet video clips

    All of the video clips are recorded at a resolution of 320 by 240. The video clips are available in two formats (as Quicktime movies and as MPEG's), and at two frame rates (30 frames per second and 15 frames per second). We suggest that you start by viewing the 15 frames per second clips, since they are smaller and quicker to download.

    All video clips are Copyright, 1997, by the Cog Shop, MIT Artificial Intelligence Laboratory, Massachusetts Institute of Technology. These clips may not be distributed, published, or rebroadcast without prior written consent.

    Footage from a Variety of Social Interaction Experiments

    Here is some 1998 footage showing Kismet engaged in social interaction with Cynthia Breazeal(Ferrell). Kismet is attending to the motion of her face or to the motion of other stimuli, and providing emotive cues to regulate the intensity of interaction.

  • Face-to-face Interaction

    This clip shows how Kismet responds when engaged in face-to-face contact with Cynthia. Kismet becomes more asocial (as shown by a disgusted expression) when Cynthia moves too much and over-stimulates Kismet. However, Kismet responds positively to an appropriate amount of stimulation.

  • Title: Face-to-face Interaction
  • Authors: Breazeal(Ferrell), Scassellati
  • Length: approximately 18 seconds
  • Quicktime (15fps) -- (3.7 Meg)
  • Quicktime (30 fps) -- (7.5Meg)
  • MPEG (15 fps) --(2.6 Meg)
  • MPEG (30fps) -- (5.1 Meg)
  • Interaction with a Slinky

    This clip shows how Kismet responds to varying amounts of slinky motion. Kismet becomes more distressed (shown by an expression of fear) when Cynthia moves the slinky too vigorously, causing Kismet to be over-stimulated. However, Kismet likes small slinky motions.

  • Title: Interaction with a Slinky
  • Authors: Breazeal(Ferrell), Scassellati
  • Length: approximately 18 seconds
  • Quicktime (15fps) -- (3.7 Meg)
  • Quicktime (30 fps) -- (7.5Meg)
  • MPEG (15 fps) --(2.6 Meg)
  • MPEG (30fps) -- (5.1 Meg)
  • Over-stimulation with a Stuffed Toy

    This clip shows how Kismet responds after being over-stimulated for an extended period of time. Because Cynthia refuses to engage Kismet at a suitable level of intensity and continues to wave the stuffed toy vigorously in front of Kismet's face, Kismet must terminate the interaction so it can restore itself to a state of homeostatic balance. To do so, Kismet shuts its eyes and goes to sleep. As it sleeps, all of its drives are restored to the balanced regieme. Once this occurs, Kismet awakens and is ready to resume interaction.

  • Title: Extended Over-stimulation Response
  • Authors: Breazeal(Ferrell), Scassellati
  • Length: approximately 18 seconds
  • Quicktime (15fps) -- (3.7 Meg)
  • Quicktime (30 fps) -- (7.5Meg)
  • MPEG (15 fps) --(2.6 Meg)
  • MPEG (30fps) -- (5.1 Meg)

  • Related Publications

    Support for this research was provided by a MURI grant under the Office of Naval Research contract N00014--95--1--0600. Early designs and implementations of the motivational system took place during a visiting appointment at the Santa Fe Institute.