According to Cialdini's principles of influence, what psychological trigger underlies the 'scarcity' principle?

According to Robert Cialdini's principles of influence, the primary psychological trigger underlying the 'scarcity' principle is 'loss aversion,' combined with the 'reactance theory.' Loss aversion, as a cognitive bias, suggests that the pain of losing something is psychologically more powerful than the pleasure of gaining something of equal value. Scarcity exploits this by implying that an item or opportunity is limited, thus creating a fear of missing out. People are motivated to take action to avoid the potential loss of not obtaining the scarce item. Reactance theory explains how individuals react to perceived threats to their freedom. When people feel their freedom to choose is being limited (e.g., by a product being scarce), they experience psychological reactance, a motivational state aimed at restoring their freedom. This often manifests as a stronger desire for the limited item. For example, a limited-time offer triggers both loss aversion (the fear of missing the deal) and reactance (the desire to restore freedom of choice before the offer expires). Therefore, scarcity works by creating a sense of urgency and a desire to secure something before it becomes unavailable, tapping into these deep-seated psychological tendencies.