Theories of love can refer to several psychological and sociological theories: * Attachment theory * Color wheel theory of love (based on the 1973 book The Colors of Love by John Lee) * Compassionate vs. passionate love theory (based on research by Elaine Hatfield) * Filter theory * Reward theory of attraction * Rubin's scale of liking and love (based on research by Zick Rubin) * Triangular theory of love * Vulnerability and care theory of love