The Haptic Creature
Emotional expression is the external display of internal affective state. The ability to communicate emotion plays an important role in social contexts by adding significance to the interaction and allowing for prediction of subsequent behavior.
Affect display in humans manifests primarily through facial, vocal, or gestural behaviors. While the study of affect display has focused mainly on vision and audition, the modality of touch has received significantly less attention.
This dearth of research at first appears counterintuitive given the unique role touch has among the other senses. For example, the skin is the largest organ in the human body; the first sense organ to form; and plays a major role in early development. In addition, unlike vision and audition, touch is proximal: it requires close or direct, physical contact to sense.
When viewed through the lens of social interaction, however, inherent difficulties of this domain become more apparent. Studies in interpersonal touch have shown various confounding factors such as gender, familiarity, social status, and culture. These sorts of studies also have been found to cause significant levels of participant discomfort.
Nonetheless, studies have found that many characteristics of social touch have emotional meaning. Furthermore, recent studies have demonstrated that humans are capable of communicating discrete emotions through touch.
Emotional expression research in socially interactive robotics has closely paralleled counterparts in psychology and sociology and, consequently, has had a similar focus on visual and auditory behaviors. The study of affect display in social human-robot interaction has been primarily on facial expressions and, to a lesser degree, on prosody of speech.
My thesis is hereby motivated by the importance of emotional expression in social human-robot interaction; however, my investigation is centered on affect display through the lesser-explored modality of touch.
As we introduce this unique sense to socially interactive robotics, however, we risk the aforementioned difficulties when studying social touch. Therefore, I have chosen to draw from models of interaction not between humans but between human and animal, whereby the robot assumes the role of animal. Furthermore, this has the added advantage of leveraging the rich patterns of non-verbal touch communication that already exist between human and animal and the long history of bonds between humans and companion animals.