Optimistic bias is commonly defined as the mistaken belief
that one's chances of experiencing a negative event are lower
(or a positive event higher) than that of one's peers. The
bias was first demonstrated by Weinstein
(1980)
xClose
Weinstein, N. D. (1980). Unrealistic optimism about future
life events. Journal of Personality and Social Psychology,
39, 806-820. , who reported that a majority of
college students believed their chances of events such as
divorce and having a drinking problem to be lower than that
of other students, and their chances of events such as owning
their own home and living past 80 years of age to be higher
than that of other students. Because a majority of individuals
in a group cannot be above (or below) the mean unless the
distribution is highly skewed, these findings represented
a bias at the level of the group. Other terms representing
the same construct include "unrealistic optimism,"
"illusion of invulnerability," "illusion
of unique invulnerability," "optimism bias,"
and "personal fable." It is also possible
to be optimistically biased by being overconfident about the
objective chances of experiencing a positive event (or avoiding
a negative event), irrespective of how one's chances compare
with those of one's peers. As noted later, optimistic bias
has been more frequently defined using the comparative definition
above due to greater methodological ease.
Subsequent work has attempted to evaluate the prevalence
of this bias as well as its determinants and moderators. Optimistic
bias has been demonstrated across a wide variety of positive
and negative events, with most work focusing on health problems
such as lung cancer, HIV infection, and alcoholism (for reviews
see Helweg-Larsen
& Shepperd, 2001
xClose
Helweg-Larsen, M., & Shepperd, J. A. (2001). Do moderators
of the optimistic bias affect personal or target risk estimates?
A review of the literature. Personality and Social Psychology
Review, 51, 74-95. ; Hoorens,
1993
xClose
Hoorens, V., & Buunk, B. P. (1993). Social comparison of health
risks: Locus of control, person-positivity bias, and unrealistic
optimism. Journal of Applied Social Psychology, 23,
291-302. ; Klein
& Weinstein, 1997
xClose
Klein, W. M., & Weinstein, N. D. (1997). Social comparison
and unrealistic optimism about personal risk. In B. P. Buunk
and F. X. Gibbons (Eds.), Health, coping, and well-being:
Perspectives from social comparison theory (pp. 25-61).
Hillsdale, NJ: Lawrence Erlbaum. ). The bias appears
in a wide variety of disparate samples including adolescents
(Quadrel,
Fischhoff, & Davis, 1993
xClose
Quadrel, M. J., Fischhoff, B., & Davis, W. (1993). Adolescent
(in)vulnerability. American Psychologist, 48, 102-117.
), community residents of varying age and socioeconomic
status (Weinstein,
1987
xClose
Weinstein, N. D. (1987). Unrealistic optimism about susceptibility
to health problems: Conclusions from a community-wide sample.
Journal of Behavioral Medicine, 10, 481-500. ),
prostitutes (van
der Velde, van der Pligt, & Hooykaas, 1994
xClose
van der Velde, F. W., van der Pligt, J., & Hooykaas, C. (1994).
Perceiving AIDS-related risk: Accuracy as a function of differences
in actual risk. Health Psychology, 13, 25-33. ),
women marines (Gerrard,
Gibbons, & Warner, 1991)
xClose
Gerrard, M., Gibbons, F. X., & Warner, T. (1991). Effects
of reviewing risk-relevant behavior on perceived vulnerability
among women marines. Health Psychology, 10, 173-179.
, and smokers (Weinstein,
1998
xClose
Weinstein, N. D. (1998). Accuracy of smokers' risk perceptions.
Annals of Behavioral Medicine, 20, 135-140. ).
Optimistic biases are more likely to emerge for events that
are controllable (Klein
& Helweg-Larsen, 2002
xClose
Klein, C. T. F., & Helweg-Larsen, M. (2002). Perceived control
and the optimistic bias: A meta-analytic review. Psychology
and Health, 17, 437-446. ) and for which people
have stereotypes of the typical person who experiences the
event (Weinstein,
1980
xClose
Weinstein, N. D. (1980). Unrealistic optimism about future
life events. Journal of Personality and Social Psychology,
39, 806-820. ). In addition, the bias is more
likely to occur when people compare themselves with aggregated
comparison targets such as "the average person" than with
more individualized comparison targets such as a friend or
even a randomly chosen person (Alicke,
Klotz, Breitenbecher, Yurak, & Vredenburg, 1995
xClose
Alicke, M. D., Klotz, M. L., Breitenbecher, D. L., Yurak,
T. J., & Vredenburg, D. S. (1995). Personal contact, individuation,
and the better-than-average effect. Journal of Personality
and Social Psychology, 68, 804-825. ). People
also hold similarly self-serving beliefs about their risk-related
behaviors such as diet and alcohol consumption (Suls,
Wan, & Sanders, 1988
xClose
Suls, J., Wan, C. K., & Sanders, G. S. (1988). False consensus
and false uniqueness in estimating the prevalence of health-protective
behaviors. Journal of Applied Social Psychology, 18,
66-79. ).
What causes optimistic bias? Some of the optimistic
bias may be attributed to cognitive factors. When comparing
their risk to that of others, people are egocentric
in that they focus more on their own risk factors than on
those of the peers to whom they are comparing (Chambers
& Windschitl, 2004
xClose
Chambers, J. R., & Windschitl, P. D. (2004). Biases in social
comparative judgments: The role of nonmotivated factors in
above-average and comparative optimism effects. Psychological
Bulletin, 130, 813-838. ); indeed, reducing such
egocentrism seems to dampen the bias (Weinstein,
1983
xClose
Weinstein, N. D. (1983). Reducing unrealistic optimism about
illness susceptibility. Health Psychology, 2, 11-20.
), and this egocentrism may lead people to be unrealistically
pessimistic about rare positive events or common
negative events (e.g., Chambers,
Windschitl, & Suls, 2003
xClose
Chambers, J. R., & Windschitl, P. D. (2004). Biases in social
comparative judgments: The role of nonmotivated factors in
above-average and comparative optimism effects. Psychological
Bulletin, 130, 813-838. ; Kruger
& Burrus, 2004
xClose
Kruger, J., & Burrus, J. (2004). Egocentrism and focalism
in unrealistic optimism (and pessimism). Journal of Experimental
Social Psychology, 40, 332-340. ). People also
seem to focus on base-rate information rather
than individual risk factors when judging the risk of their
peers (Klar,
Medding, & Sarel, 1996
xClose
Klar, Y., Medding, A., & Sarel, D. (1996). Nonunique invulnerability:
Singular versus distributional probabilities and unrealistic
optimism in comparative risk judgments. Organizational
Behavior and Human Decision Processes, 67, 229-245. ),
and they may come to see any individual member of a group
as discrepant because they compare individuals to general
rather than local standards (Klar,
2002
xClose
Klar, Y. (2002). Way beyond compare: Nonselective superiority
and inferiority biases in judging randomly assigned group
members relative to their peers. Journal of Experimental
Social Psychology, 38, 331-351. ).
However, there are also reasons to believe that optimistic
biases derive from motivational causes such
as a need to protect self-esteem because people engage in
numerous strategies to protect these and related beliefs when
challenged (e.g., Boney-McCoy,
Gibbons, & Gerrard, 1999
xClose
Boney-McCoy, S., Gibbons, F. X., & Gerrard, M. (1999). Self-esteem,
compensatory self-enhancement, and the consideration of health
risk. Personality and Social Psychology Bulletin, 25,
954-965. ; Croyle,
Sun, & Louie, 1993
xClose
Croyle, R. T., Sun, Y., & Louie, D. H. (1993). Psychological
minimization of cholesterol test results: Moderators of appraisal
in college students and community residents. Health Psychology,
12, 503-507. ; Gerrard,
Gibbons, Benthin, & Hesling, 1996
xClose
Gerrard, M., Gibbons, F. X., Benthin, A. C., & Hessling, R.
M. (1996). A longitudinal study of the reciprocal nature of
risk behaviors and cognitions in adolescents: What you do
shapes what you think, and vice versa. Health Psychology,
15, 344-354. ; Klein
& Weinstein, 1997
xClose
Klein, W. M., & Weinstein, N. D. (1997). Social comparison
and unrealistic optimism about personal risk. In B. P. Buunk
and F. X. Gibbons (Eds.), Health, coping, and well-being:
Perspectives from social comparison theory (pp. 25-61).
Hillsdale, NJ: Lawrence Erlbaum. ; Kunda,
1987
xClose
Kunda, Z. (1987). Motivated inference: Self-serving generation
and evaluation of causal theories. Journal of Personality
and Social Psychology, 53, 636-647. ), making
optimistically biased judgments highly resistant to change
(Weinstein
& Klein, 1995
xClose
Weinstein, N. D., & Klein, W. M. (1995). Resistance of personal
risk perceptions to debiasing interventions. Health Psychology,
14, 132-140. ). Emotion also plays a role; for
example, people are more likely to be optimistically biased
when angry and less likely when fearful or sad (Lerner
& Keltner, 2001
xClose
Lerner, J. S., & Keltner, D. (2001). Fear, anger, and risk.
Journal of Personality and Social Psychology, 81,
146-159. ; Salovey
& Birnbaum, 1989
xClose
Salovey, P., & Birnbaum, D. (1989). Influence of mood on health-relevant
cognitions. Journal of Personality and Social Psychology,
57, 539-551. ).
Importance in health behavior models.
Perceived vulnerability is a key component of many health
behavior models including the Health Belief Model
(Janz
& Becker, 1984
xClose
Janz, N. K., & Becker, M. H. (1984). The health belief model:
A decade later. Health Education Quarterly, 11, 1-47.
), Protection Motivation Theory (Rogers,
1983
xClose
Rogers, R. W. (1983). Cognitive and physiological processes
in fear appeals and attitude change: A revised theory of protection
motivation. In J. T. Cacioppo & R. E. Petty (Eds.), Social
psychophysiology (pp. 153-176). New York: Guilford Press.
), the Precaution Adoption Process Model
(Weinstein,
1988
xClose
Weinstein, N. D. (1988). The precaution adoption process.
Health Psychology, 7, 355-386. ), and the
Prototype/Willingness Model (Gibbons,
Gerrard, & Lane, 2003
xClose
Gibbons, F. X., Gerrard, M., & Lane, D. J. (2003). A social
reaction model of adolescent health risk. In J. M. Suls &
K. Wallston (Eds.), Social psychological foundations of
health and illness (pp. 107-136). Oxford: Blackwell.
). Based on these models, if people underestimate their
risk of experiencing a negative health outcome, they will
be less likely to take precautions to prevent that outcome
from occurring. Thus, given that optimistic biases represent
an underestimation of risk, it may be argued that such biases
are maladaptive. However, a different line of research suggests
that positive illusions such as the optimistic bias may be
adaptive because they promote motivation and discourage placidity
(Armor
& Taylor, 1998
xClose
Armor, D. A., & Taylor, S. E. (1998). Situated optimism: Specific
outcome expectancies and self-regulation. Advances in
Experimental Social Psychology, 30, 309-379. ).
The notion that underestimations of risk may either hinder
or promote precautionary behavior may explain why risk perceptions
are often only moderately predictive of behavior (Gerrard,
Gibbons, & Bushman, 1996
xClose
Gerrard, M., Gibbons, F. X., & Bushman, B. J. (1996). Relation
between perceived vulnerability to HIV and precautionary sexual
behavior. Psychological Bulletin, 119, 390-409. ;
McCaul,
Branstetter, Schroeder, & Glasgow, 1996
xClose
McCaul, K.D., Branstetter, A. D., Schroeder, D. M., & Glasgow,
R. E. (1996). What is the relationship between breast cancer
risk and mammography screening? A meta-analytic review. Health
Psychology, 15, 423-429. ). It is likely that
optimistic biases have differential effects on health behavior
depending on many variables that have yet to be identified,
providing a fruitful area of future research.
|