“My-side bias” makes it difficult for us to see the logic in arguments we disagree with

By Christian Jarrett

In what feels like an increasingly polarised world, trying to convince the “other side” to see things differently often feels futile. Psychology has done a great job outlining some of the reasons why, including showing that, regardless of political leanings, most people are highly motivated to protect their existing views.

However a problem with some of this research is that it is very difficult to concoct opposing real-life arguments of equal validity, so as to make a fair comparison of people’s treatment of arguments they agree and disagree with.

To get around this problem, an elegant new paper in the Journal of Cognitive Psychology has tested people’s ability to assess the logic of formal arguments (syllogisms) structured in the exact same way, but that featured wording that either confirmed or contradicted their existing views on abortion. The results provide a striking demonstration of how our powers of reasoning are corrupted by our prior attitudes.

Vladimíra Čavojová at the Slovak Academy of Sciences and her colleagues recruited 387 participants in Slovakia and Poland, mostly university students. The researchers first assessed the students’ views on abortion (a highly topical and contentious issue in both countries), then they presented them with 36 syllogisms – these are formal logical arguments that come in the form of three statements (see examples, below).

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The participants’ challenge was to determine whether the third statement of each syllogism followed logically from the first two, always assuming that those initial two premises were true. This was a test of pure logical reasoning – to succeed at the task, one only needs to assess the logic, putting aside one’s prior knowledge or beliefs (to reinforce that this was a test of logic, the participants were instructed to always treat the first two premises of each syllogism as true).

Crucially, while some of the syllogisms were neutral, others featured a final statement germane to the abortion debate, either on the side of pro-life or pro-choice (but remember this was irrelevant to the logical consistency of the syllogisms).

Čavojová and her team found that the participants’ existing attitudes to abortion interfered with their powers of logical reasoning – the size of this effect was modest but statistically significant.

Mainly the participants had trouble accepting as logical those valid syllogisms that contradicted their existing beliefs, and similarly they found it difficult to reject as illogical those invalid syllogisms that conformed with their beliefs. This seemed to be particularly the case for participants with more pro-life attitudes. What’s more, this “my-side bias” was actually greater among participants with prior experience or training in logic (the researchers aren’t sure why, but perhaps prior training in logic gave participants even greater confidence to accept syllogisms that supported their current views – whatever the reason, it shows again what a challenge it is for people to think objectively).

“Our results show why debates about controversial issues often seem so futile,” the researchers said. “Our values can blind us to acknowledging the same logic in our opponent’s arguments if the values underlying these arguments offend our own.”

This is just the latest study that illustrates the difficulty we have in assessing evidence and arguments objectively. Related research that we’ve covered recently has also shown that: our brains treat opinions we agree with as facts; that many of us over-estimate our knowledge; how we’re biased to see our own theories as accurate; and that when the facts appear to contradict our beliefs, well then we turn to unfalsifiable arguments. These findings and others show that thinking objectively does not come easily to most people.

My point is valid, yours is not: myside bias in reasoning about abortion

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest

20 thoughts on ““My-side bias” makes it difficult for us to see the logic in arguments we disagree with”

  1. //“Our results show why debates about controversial issues often seem so futile,” the researchers said. “Our values can blind us to acknowledging the same logic in our opponent’s arguments if the values underlying these arguments offend our own.”//

    To be honest I think that my opponents simply lack any logic rather than me being unable to see it.

  2. Thank you for the great article! Has there been any similar study that tries to find a solution to this problem? As in, how to diminish this my-side bias?

    Thanks again!

    1. Hi Justin – I’ve been developing a programmatic solution for this issue, a platform that can sift through choices and behaviours in a consensus process that can edit out ‘my side’ bias. From my POV, some of this phenomenon is environmental and given a set of choices and an environment that is more conducive to “rational consensus”, some will readjust. We live in a time where consensus building is probably one of the more critical issues we need to focus on – I too am happy to see more research come out about this.


  3. Um. No. It’s because people have lost all respect for other’s opinions. That sort of climate creates dissonance.

  4. I’ve been developing a platform for online consensus building for quite some time, specifically the past four years I’ve been highly engaged with online consensus building in toxic social groups. It is awesome to see more research come out about this. Speaking from direct experience only, I’ve been somewhat shocked at the degree this phenomenon occurs regardless of what ideological side of the fence the person happens to be. http://wikipediawehaveaproblem.com/2018/09/internet-drama-a-consensual-field-study-into-online-consensus-building/

    1. I’d be interested to know whether there were other correlations, age, IQ, gender?

  5. This is fascinating. I’m finding it hard to read some of these logically, without my brain interrupting, giving it’s opinion, as to whether or not I agree, morally, with the sentence.
    It’s like the logic side of my brain is trying to figure out if the last one follows from the others, but the emotional side is butting in saying “hey, I agree with that one, but not the other one”!

  6. I don’t get this. Accuracy for both valid and invalid syllogisms was practically the same for the “neutral” example and the “controversial” ones. It looks to me as though this study is proving the exact opposite of what the article claims.

      1. But we don’t know what the participants existing attitudes to abortion were, do we? The only details we have are that the researchers chose a “a highly topical and contentious issue” subject around which to construct some of the syllogisms. But we don’t know that the participants thing abortion is “a highly topical and contentious issue”. Just that it is a “a highly topical and contentious issue” in those countries.

        There are two types of syllogism in this “study”:

        1. Neutral ones presumably to act as control.
        2. The “controversial” ones to test for bias.

        But they lead to very different syllogisms. Some of the ones round abortion are so poorly written as to be barely intelligible at all. So it’s not really surprising that some of the participants got those “wrong”.

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