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Only My Opinion Counts: Myside Bias, Part 2

Only My Opinion Counts: Myside Bias, Part 2A common error that occurs with everyday thinking is Myside Bias — the tendency for people to evaluate evidence, generate evidence, and test hypotheses in a manner biased toward their own opinions. Part 1 looked at the correlation between myside bias and intelligence. Part 2 examines other factors that may contribute to myside bias.

In a series of experiments, Stanovich and West (2008) examined the association between cognitive ability and two key critical thinking skills: avoidance of myside bias and avoidance of oneside bias (when people prefer one-sided arguments over arguments presenting multiple perspectives). 

In Experiment 1, natural myside bias was investigated in 15 different propositions. In Experiment 2, myside bias and one-sided bias was studied. In Experiment 3, associations between thinking dispositions, in addition to cognitive ability, and one-sided and myside bias were investigated.

In Experiment 1, the researchers concluded, there was “no evidence at all that myside bias effects are smaller for students of higher cognitive ability” (p. 140).

The main purpose of Experiment 2 was to investigate the association of cognitive abilities with myside and oneside bias. “The results… were quite clear-cut. SAT total scores displayed a nonsignificant 7.03 correlation with the degree of myside bias and a correlation of .09 with the degree of one-side bias (onebias1), which just missed significance on a two-tailed test but in any case was in the unexpected direction” (p. 147). It was also revealed that stronger beliefs usually imply heavier myside bias.

In Experiment 3 “the degree of myside bias was uncorrelated with SAT scores,” and “[t]he degree of one-side bias was uncorrelated with SAT scores” (p. 156). Myside bias was weakly correlated with thinking dispositions. Oneside bias showed no correlation with thinking dispositions.

The final two sentences or the research report read: “Our results thus indicate that intelligence — as defined by traditional psychometric indicators — turns out to be surprisingly independent of critical thinking tendencies. Cognitive ability measures such as the SAT thus miss entirely an important quality of good thinking” (p. 161). The good news is critical thinking abilities are malleable, and in fact, probably more malleable than intelligence.  Avoidance of oneside bias is another rational thinking skill that is not related to intelligence.   

Hybrid Reasoning Deficiency

Myside bias is derived from a focal bias and from contaminated mindware that causes us to look at the world from an egocentric perspective.  A focal bias occurs when one focuses on a mental model or frame already formed.  The mental model is taken as focal and all subsequent reasoning is based on this model rather than alternatives; the latter would be too computationally expensive (require too much thinking).  Egocentrism involves taking our thoughts and projecting them onto the minds of others. 


Several studies have shown no correlation between intelligence and myside bias.  Overconfidence effects leading to focal bias has been modestly associated with intelligence in a few studies.  In these studies, participants with higher intelligence have shown slightly lower overconfidence.  ”Again, though, these are statistically significant but modest associations — ones that leave plenty of room for the dissociation that defines dysrationalia in this domain (highly unwarranted overconfidence in an individual of high intelligence)” (Stanovich, 2009, p. 114). 

The strongest evidence for the lack of association between intelligence and myside bias comes from studies investigating what Stanovich and West term natural myside bias.  Natural myside bias is displayed when information is evaluated in a biased manner when no instructions or cues are given to avoid doing so (typical performance conditions). 

However, it is highly likely that individuals with higher intelligence would show less myside bias if they were told they should take multiple perspectives or to avoid biased thinking (optimal performance conditions). 

If you tell an intelligent person what the rational requirement is they are likely to do better than a less intelligent person.  But, concerning myside bias and many other rational thinking skills, when given no explicit cues (as in everyday judgment and decision making) of the rational requirement intelligent people do no better than less intelligent people.  It is also important to distinguish between within-group designs and between-group designs.  The former may provide cues to what the rational requirement is, whereas the latter does not contains cues.      

You can also read Part 1 of this essay about myside bias.


Stanovich, K., West, R. (2008).  On the failure of cognitive ability to predict myside and oneside thinking biases.  Thinking & Reasoning, 14 (2), 129 – 167

Stanovich, K. E. (2009). What intelligence tests miss: The psychology of rational thought. New Haven, CT: Yale University Press.

Only My Opinion Counts: Myside Bias, Part 2

Jamie Hale, M.S.

Jamie Hale, MS., is a researcher specializing in eating behavior, cognitive science (various aspects) and scientific reasoning. Jamie has written seven books and co-authored one. He is a member of the World Martial Arts Hall of Fame (recognition of my strength and conditioning work with martial artists), college instructor, learning / memory consultant and board member of Kentucky Council Against Health Fraud.

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APA Reference
Hale, J. (2018). Only My Opinion Counts: Myside Bias, Part 2. Psych Central. Retrieved on September 29, 2020, from
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Last updated: 8 Jul 2018 (Originally: 18 Sep 2011)
Last reviewed: By a member of our scientific advisory board on 8 Jul 2018
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