Jealousy can either be suspicious or reactive, and it is often reinforced as a series of particularly strong emotions and constructed as a universal human experience. Psychologists have proposed several models to study the processes underlying jealousy and have identified factors that result in jealousy. Sociologists have demonstrated that cultural beliefs and values play an important role in determining what triggers jealousy and what constitutes socially acceptable expressions of jealousy. Biologists have identified factors that may unconsciously influence the expression of jealousy.