With all that in mind, Haidt identified five foundational moral impulses. As succinctly defined by Northwestern University's McAdams, they are:

• Harm/care. It is wrong to hurt people; it is good to relieve suffering.

• Fairness/reciprocity. Justice and fairness are good; people have certain rights that need to be upheld in social interactions.

• In-group loyalty. People should be true to their group and be wary of threats from the outside. Allegiance, loyalty and patriotism are virtues; betrayal is bad.

• Authority/respect. People should respect social hierarchy; social order is necessary for human life.

• Purity/sanctity. The body and certain aspects of life are sacred. Cleanliness and health, as well as their derivatives of chastity and piety, are all good. Pollution, contamination and the associated character traits of lust and greed are all bad.

Haidt's research reveals that liberals feel strongly about the first two dimensions -- preventing harm and ensuring fairness -- but often feel little, or even feel negatively, about the other three. Conservatives, on the other hand, are drawn to loyalty, authority and purity, which liberals tend to think of as backward or outdated. People on the right acknowledge the importance of harm prevention and fairness but not with quite the same energy or passion as those on the left.