Other International Definitions
Optimism bias relates to the perception of personal invulnerability, representing the underestimation of the likelihood of experiencing negative events It represents a defensive distortion that can undermine preventive actions.  Optimism bias can therefore be considered a form of indirect denial of risk. It is a concept that is frequently cited in research on risk and is an individual factor influencing Risk Perception.  
- Weinstein, N. (1984). Why it won’t happen to me: Perceptions of risk factors and susceptibility. Health Psychology, 3, 431-457.
- Weinstein, N.D. & Klein, W.M. (1996). Unrealistic optimism: present and future. Journal of Social and Clinical Psychology, 15, 1-8.
- Schwarzer R. (1994). Optimism, vulnerability, and self-beliefs as health related cognitions: a systematic overview. Psychology and Health, 9, 161-180.
- Lopes, L. L. (1995). Algebra and process in the modelling of risky choice. In J. Busemeyer & R. Hastie & D. L. Medin (Eds.), Decision making from a cognitive perspective. San Diego CA: Academic Press.
- McKenna, F. P. (1993). It Won’t Happen to Me: Unrealistic Optimism or Illusion of Control. British Journal of Psychology, 84, pp 39–50.