“…Psychophysiological approaches that have been productive in developmental research on children's responses to other types of stimuli (Fox, Schmidt, Henderson, & Marshall, 2007;Jones & Gagnon, 2007) may be especially appealing for their potential to unlock meaning in quantitative and qualitative differences in presentations of jealousy, and, more generally, toward illuminating an intrapersonal experience that is too multifaceted to be articulated by the young child. Thus, psychophysiological measures offer potential to shed light on the significance of affect expressions that are atypical, on affective displays that are lacking in expressivity, and possibly on discrete emotions, such as love, where affective experiences do not correspond in one-to-one fashion with any known facial expression (Aviezer et al, 2008;Barrett, Mesquita, Ochsner, & Gross, 2007;Camras et al, 2007;Camras & Shutter, under review;Eysenck, 1967;Field, 1996). Based on our observations of wide individual differences in the presentation of nascent jealousy, as well as the exquisite sensitivity and sheer intensity of what appears as raw passion in some infants, we would hazard to predict that efforts to unravel the socialization of jealousy and to comprehend conditions under which it goes awry will not be fully productive without deeper insight into the ''physiological fire'' that is jealousy's constitutional foundation.…”