  What breathes life into an embodied agent or avatar? While body motions such
as facial expressions, speech and gestures have been well studied, relatively
little attention has been applied to subtle changes due to underlying
physiology. We argue that subtle pulse signals are important for creating more
lifelike and less disconcerting avatars. We propose a method for animating
blood flow patterns, based on a data-driven physiological model that can be
used to directly augment the appearance of synthetic avatars and
photo-realistic faces. While the changes are difficult for participants to
"see", they significantly more frequently select faces with blood flow as more
anthropomorphic and animated than faces without blood flow. Furthermore, by
manipulating the frequency of the heart rate in the underlying signal we can
change the perceived arousal of the character.
