Subtle expressivity for characters and robots
People, both consciously and unconsciously, use subtle expressions to indirectly communicate their emotions and intentions through variations of the gaze direction, voice tone and gesture speed. People also perceive changes in the internal states of others from subtle changes in their expressivities while interacting with them. Subtle expressivity plays the supporting part to the leading role of explicit expressivity, such as contents of speech or category of facial expressions. However, subtle expressivity plays an important role to give moderate effects or gently regulate the relationship among the participants through a continuous interaction. These subtle expressivities are little focused on the design of interactive media in the context of software products and computers. Only in the area of computer games in which pre-designed animated characters are used, the full potential of subtle expressivity is fully understood and used. Although the general interest of the human-computer interaction research community in life-likeness and personality as a goal of software design is growing for reducing cognitive load [1,2], we are far from having coherent understanding of what subtle expressivity actually is and how products and processes can address it. We might question whether designing for subtle expressivity will result in gentle emotional effects on people and whether the processes and topics involved differ in any significant way from designing for believability or personality.