Moral sense is difficult to study because there is no agreed upon definition of it. Some definitions exclude non-human animals from having a moral sense by requiring explicit rules, religion, or human-specific methods for applying sanctions and punishment. This entry leaves such definitions up to the reader, and instead focuses on relating the human moral sense to similar behaviors in other animals.
Many animals possess a sense that some set of actions are acceptable or expected ("right"), that others are unacceptable ("wrong"), and that these implicit rules of action apply to other individuals, often based on social status. These sets of "right" and "wrong" actions persist over long periods of time. The flexibility of these rules is not well-studied outside of humans, but these rules tend to be related to group cohesion (see social contract theory). These actions are intimately tied with emotional responses in all animals, including humans. Many studies of this sense assume that these behaviors improve group cohesion and, and so relate this to other social behaviors thought to be beneficial to group cohesion (such as reciprocity, cooperation, peacefulness, having social standards and methods for sanctioning) and keep it separate from social behaviors thought to be more arbitrary and less clearly beneficial (such as empathy and fairness).
In humans, moral sense is elaborated in many ways. These rules can be abstracted away from action and involve intention or thought. The rules show some flexibility across groups, such that some groups include rules for actions or ideas that other groups have no rules for; the flexibility of inclusion/exclusion is used as a basis for in-group and out-group relations. There is also flexibility in the sanctions applied to in-group members who fail to follow the rules and in how to interact with out-group members. Nearly all human societies incorporate uniquely human capacities into codifying a shared morality, producing laws that require its inhabitants to act morally for fear of punishment (including punishment carried out by a third-party), censure or acquiring a bad reputation.
Another dichotomy introduced by authors is between momentary decision-making in a behavioral context and deliberative decision-making across a long period of time. Evidence of a non-human moral sense seems to fit the momentary, contextual aspect of moral sense, while humans seem to make both types of judgments. In the human case, feedback from deliberative decision-making can be used as a learning signal to create a level of consistency between the two faculties of judgment. These two faculties operate at different time-scales, seem to rely on different cognitive abilities and some different neurobiological structures, and therefore seem to be dissociable. This suggests that the human moral sense is not a unitary concept, and that some equivocation occurs in most discussions where these two aspects are not presented as distinct.
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Braintrust: What Neuroscience Tells Us about Morality, , Princeton, N.J., p.273, (2011)
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Only humans have morality, not animals, , (2011)
Wild Justice: The Moral Lives of Animals, , p.204, (2010)
Animals can tell right from wrong, , (2009)