This advertisement from Cadbury uses the 'Scarcity' principle as a persuasion technique. The advert uses the phrase ‘creme egg season 1st Jan-4th of April’ to highlight that creme eggs are available for a limited period and ‘here today, goo tomorrow’ to suggest that they will be gone soon. According to the reactance theory whenever free choice is limited we feel the need to retain our freedom, which makes us want the limited item significantly more (Brehm & Brehm, 1981).
Evidence for the influence of the scarcity principle has been demonstrated by Brehm & Weintraub (1977). They found that toddlers who had the opportunity to play with an easy to access and hard to access toy showed a preference for the hard to access toy. In fact, they touched the hard to access toy three times faster than toddlers who had easy access to both toys.
Brehm, S. S., & Weintraub, M. (1977). Physical barriers and psychological reactance. Two-year-olds’ responses to threats to freedom. Journal of Personality and Social Psychology, 35, 830–836.
Brehm, S. S., & Brehm, J. W. Psychological Reactance: A theory of Freedom and Cnotrol, New York: Academic Press, 1981.