Paul Ekman (1999) argues that shame deserves to be labelled as one of fifteen basic emotions and that it and the other fourteen are “distinguishable one from another: amusement, anger, contempt, contentment, disgust, embarrassment, excitement, fear, guilt, pride in achievement, relief, sadness/distress, satisfaction, sensory pleasure, and shame.” His research did not uncover precisely what distinguishes these apart, except for universal expressions for Sadness, Surprise, Anger, Disgust, Fear, Happiness and Sadness. Nor did his work reveal universal signals of shame, though he argued eight years later that shame fits within the sadness family. This is likely to do with the universal trigger of sadness being loss of something of value. In the case of shame it may be loss of ‘face’.
Hacker (2017) develops this argument and posits that “shame is an emotion of concealment. It is prototypically a social emotion. The primitive roots of the emotion of shame lie in the loss of face felt to be incurred by being seen, by others—primarily, but not only, by members of one’s peer group—when one is in an indecorous condition that should be concealed from public eyes; or when one is engaged in an activity that reveals one’s failure to attain standards of competence that others demand of one or one demands of oneself; or when one fails to live up to standards of the honor code of one’s peer group and that one accepts oneself”.
He outlines the potential roots of shame with a useful schematic:
I would put forward a theoretical argument, yet to be determined by empirical research, that shame might be a blend of sadness and embarrassment. This may be the pathway to identifying universal expressions, which we already have for sadness.
Charles Darwin provided a starting point over one hundred and forty years ago when he suggested that the behavioral manifestations of shame are common to feeling embarrassed (and to feeling shy as well).
Hacker (2017) summarises this well by highlighting that a characteristic of embarrassment, shame and shyness “is blushing, which, according to Darwin, is a uniquely human non‐voluntary response. Remarkably, it is not only a non‐voluntary reaction, but the self‐conscious wish to restrain it actually exacerbates it. Such blushing is normally accompanied by a degree of emotional perturbation, a sense of discomfort, and a wish ‘to disappear’ or ‘to sink into the ground.’ The characteristic behavioral accompaniments are eye‐contact avoidance, either by deliberately averting one’s gaze (especially in the case of feeling shame or embarrassment), or by casting one’s eyes down (especially when feeling shy in company). In all three cases, one’s movements are prone to be awkward and nervous. One’s vocal reactions may involve stammering. Often hands will be put up to the face to conceal a blush or to cover the eyes. Such behavioral responses are the characteristic criteria for these three kinds of occurrent emotions, the differentiation of which depends upon additional behavioral criteria, upon the context and antecedent history of the episode, and upon the object and intention of the emotion.”
My bold emphasis added to suggest potential behavioural indicators of shame.
So, although reliable primary research that highlights universal indicators of shame does not seem to be available, the theoretical blend of sadness and shame might suggest that the behavioural indicators that may result from such research could include:
A good PhD here for someone?
 Kaufman, G., 1992. Shame: The power of caring(p. p8). Rochester, VT: Schenkman Books.
 Tomkins, S.S., 1984. Affect theory. Approaches to emotion, 163(163–195).
 Ekman, P., 1999. Basic emotions. Handbook of cognition and emotion, pp.45-60.
 Ekman, P., 2007. Emotions revealed: Recognizing faces and feelings to improve communication and emotional life. Macmillan.
 Hacker, P., 2017. Shame, Embarrassment, and Guilt. Midwest Studies In Philosophy, 41(1), pp.202-224.
 Darwin, C., 1872. 1965. The expression of the emotions in man and animals. London, UK: John Marry.