Abstract: In this paper we examine to what extent the lengths of the links in an animated articulated-figure can be changed without the viewer being aware of the change. This is investigated in terms of a framework that emphasizes the role of attention in visual perception. We conducted a set of five experiments to establish bounds for the sensitivity to changes in length as a function of several parameters and the amount of attention available. We found that while length changes of 3% can be perceived when the relevant links are given full attention, changes of over 20% can go unnoticed when attention is not focused in this way. These results provide general guidelines for algorithms that produce or process character motion data and also bring to light some of the potential gains that stand to be achieved with attention-based algorithms.