There is a prevailing notion that the emotional life of children with ASD is dominated by negative emotions. Such a negative affectivity bias may have a profound effect on attention, learning, and social interactions. Yet, research has focused primarily how children with ASD discriminate and understand the emotions of others or strategies they use to regulate their own emotions, rather than on how they react emotionally to the world around them. Thus, little is known about the intensity, valence, and congruency of emotions in response to real-world events in children with ASD, particularly during the early stages of the disorder. Understanding emotional expressivity and their links with attention and physiology will improve our grasp of the inner lives of toddlers with ASD and inform clinical practice and theory by identifying affective factors shaping their developmental trajectories. The multidisciplinary panel of junior and senior researchers will present never-published data from an ongoing large, prospective study of attentional, physiological, and emotional processes underlying early affective development in ASD. The results reveal complex and surprising emotional profiles of toddlers with ASD and show feasibility and reliability of the behavioral, attentional, and physiological measures for studying the emotional lives of toddlers with social disabilities.