Uncommon Sense

We and others often preface our remarks with "It's a no brainer" or "You don't have to be a rocket scientist" when attempting to underscore the obviousness of an opinion. That tendency is a variant of what Daniel Kahneman (2013) calls System 1 thinking - fast, automatic, sometimes unconscious thoughts.  System 1 thinking is not too distant from intuition.  All of this suggests that we mostly prefer not to think too deeply about things.  And, not thinking too deeply usually is sufficient for coping with routine, low-risk activities of daily life.  On the other hand, System 1-like thought can lead us into trouble when activities are non-routine and/or risky.

Duncan Watts (2011) shares the aforementioned concerns, although he refers to them as errors of "common sense."  He cites, for example, a 1940s study by sociologist Paul Lazarsfeld in which respondents were deceived to believe that most rural recruits adjusted better to the army than did urban ones.  Those thus told concluded post hoc that the result was obvious, mentioning, for instance, rural men's comfort with outdoors and weapons, among other things.  However, the study actually found the opposite - that urban men adjusted better than rural ones.  So, common sense failed the empirical test.

Please do not conclude that Watts endorsed learning from history as an antidote to relying on common sense.  Rather, he wrote, and I agree, that "lessons" from history often are no more applicable than is common sense.  Every event is unique, if only in its context.  You may have heard that generals spend their time trying to prevent the previous war and financial institutions, the previous financial crisis.  And neither succeed in preventing the ones that ultimately occur.

No significant issue that appears in your consciousness is a "no brainer."  You are conscious of the issue because it has the potential to affect your wellbeing.  Even something as routine and trivial as whether you should have a second slice of cake is worth your deliberate consideration.  If you are aware of an impending decision, your choice should follow after you think the issue through.  Thinking about your history of cake eating also is insufficient.  There have been times when your daily diet and/or exercise regimen impacted the second piece of cake decision in a positive direction and others in a negative direction, neither of which might apply currently.  Whether you had a second piece last week might be totally irrelevant presently.

Your current condition is what matters.  The more you mindlessly continue to persist in self-defeating behaviors due to your reliance on "common sense" opinion or your history, the more you reinforce those negative behaviors, and the harder it will be to make healthful choices in the future.  The relevance of common sense and your history should be weighed after, not before, you have thought through the presenting issue within its current context. 

References

 Kahneman, D.  (2013),  Thinking Fast and Slow. New York: Penguin.

Watts, D. (2011). Everything Is Obvious: How Common Sense Fails Us.  New York: Crown.