The Walt Disney Tigger is a very expressive character capable of using both verbal and nonverbal means of communication. His face has eyebrows that go up and down, and a huge mouth that can curl itself into the saddest frown or stretch into the happiest smile. Additionally, Disney's Tigger uses body language, the position of his ears and the hunch in his back to outwardly show when he is perked up happy or drooping down sad [Thomas, 1995]. Tiger's vocalizations also include non verbal cues of emotion. There is the happy ``worraworraworra'' growl when Tigger is in an especially good mood, and the sniveling *sigh* he makes when he is unhappy.
The Affective Tigger's expressive capability is presently limited to happy, neutral, and unhappy. While children have and can express many different emotions from very early on, the happy, neutral, and unhappy emotions are the most immediate, and can be directly coupled to good and bad. ``Young children are likely to rely on cognitively uncomplicated emotions such as happy and sad which are not only early elements of a child's emotional lexicon but can also be easily understood due to their reliance on a straightforward assessment of success of failure'' [Saarni and Harris, 1989]. When the child makes the Affective Tigger `unhappy', he exhibits that unhappiness in his ears and in his voice. As researchers we can observe the child's response to an unhappy Tigger immediately and directly. While moods often take a long time to develop, and persist for many minutes, the immediacy of the Affective Tigger's response to the child's behavior gives the child, and by extension the researchers, direct feedback.
Due to the vagueness of the Affective Tigger's behavior, the cause of his emotional states are left open to the user's interpretation. This is one of the biggest advantages to the toy, because it allows the child to use her imagination to invent stories surrounding why she has caused the Affective Tigger to be unhappy today, or especially happy. As the child becomes increasingly familiar with the Affective Tigger she will impart upon his behavior a semblance of a personality. She might call him `silly' or `easily upset', or refer to him with other categorizations that were not directly built-in.
Tigger's most expressive characteristic is his face. From the extra happy and bouncy Tigger to the sad humble de-bounced Tigger, what changes most dramatically is his posture. I capitalized on this preexisting personality trait by animating the large ears of the plush I was working with. This manner of expression is closely associated with cartoon characters in general, and Tigger in specific [Thomas, 1995]. In conjunction with other emotionally charged cues such as a drooping head, the act of bouncing, and other situational contexts and story lines, the motion of the Affective Tigger's ears provide a compelling visual sign of his emotional state. This is in addition to the Affective Tigger's vocal expressivity.
The ears have three positions for each of Tigger's three emotional displays: happy (see figure 2-1), neutral (see figure 3-3), and unhappy (see figure 2-3). There is a stiff wire attached to a small servo motor inside Tigger's head, such that as the wire rotates, the ears move through the three positions.
Two separate servo motors would permit the Affective Tigger to look
confused by putting one of his ears up while the other is down. The
addition of a confused state is a tangent to the three primary moods
of the Affective Tigger, and was determined to be unnecessary for this
study. The use of two servos introduced excessive power requirements,
space demands, too much extra noise, and was a major part of the cost
of the toy
. The Affective Tigger
would have become confused when the child bounces him in a happy
manner during a sad mood, or gave other mixed signals.
A string attached to the Affective Tigger's jaw is pulled in coordination with the movement of the ears by the servo motor. During unhappy moods, the Affective Tigger closes his mouth. The closed mouth augments the illusion of unhappiness, whereas the open mouth incurs a happy expression.
Sound in general, and voice in particular, is a very important piece of the interaction between young children and their toys [Erikson, 1977]. The Affective Tigger has four vocalizations (see section 3.2.2), two with happy overtones and two with unhappy ones. When exceptionally happy, the Affective Tigger says, ``a hoo hoo hoo hoooo, wheeee...''. When happy he says, ``that's what Tigger's like best!''. Making the Affective Tigger unhappy elicits a growl, and when very unhappy he will say, ``Stop that, kid, please, `S' `T' `O' `P' STOP!''
The second version of The Affective Tigger included an Airtronic servo motor, housed in a specially designed encasement within Tigger's body. Flexible push rods in Tigger's spine controlled the ear movements. A rubber ball in Tigger's head shielded the moving joints from impact and excessive fluff.
The controller is a HANDY board [Martin, 1998] running IC
(a subset of the C programming language designed specifically for the
6.270 robot contest at MIT). The processor is a Motorola HC11. Chris
Metcalfe provided the vocal Tigger imitations resident on a ISD 1020
voice record/playback chip.
