International Journal of Synthetic Emotions, 3(1), 1-17, January-June 2012 1 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Keywords: Emotion, Emotional State, Gtrace, Perceived Effect, Tracing Emotion INTRODUCTION A decade ago, our group used research on human emotion to argue that continuous representations were a natural tool for affective computing (Cowie et al., 2001). The idea has worn well, and there is growing interest in the problem of using signs in various modalities to construct a ‘trace’ that describes how a target person’s emotional state appears to be rising and falling from moment to moment. However, problems at the human end have been perhaps unexpectedly obstinate. Progress depends on databases that provide traces reflecting human judgments, so that machines can use them as models. Acquir- ing suitable traces poses problems which are both substantial and interesting. The aim of this paper is to provide an overview of the issues involved in acquiring traces from human raters, and the techniques available to solve them. Among those is a new system for acquiring traces, Gtrace, designed to capitalise on the lessons described here. Some of the issues are well known in psychology, and are dealt with in sources such as Rosenthal (2005). Others are specific to the particular technique, and have not been dealt with in a systematic way before. Tracing Emotion: An Overview Roddy Cowie, Queen’s University Belfast, UK Gary McKeown, Queen’s University Belfast, UK Ellen Douglas-Cowie, Queen’s University Belfast, UK ABSTRACT Computational research with continuous representations depends on obtaining continuous representations from human labellers. The main method used for that purpose is tracing. Tracing raises a range of chal- lenging issues, both psychological and statistical. Naive assumptions about these issues are easy to make, and can lead to inappropriate requirements and uses. The natural function of traces is to capture perceived affect, and as such they belong in long traditions of research on both perception and emotion. Experiments on several types of material provide information about their characteristics, particularly the ratings on which people tend to agree. Disagreement is not necessarily a problem in the technique. It may correctly show that people’s impressions of emotion diverge more than commonly thought. A new system, Gtrace, is designed to let rating studies capitalise on a decade of experience and address the research questions that are opened up by the data now available. DOI: 10.4018/jse.2012010101