Confirmation Bias

“The kids are crazy today it must be a full moon.”    This and other similar notions are widely held.  For example, people working in Emergency Departments (ED) assume that spikes in ED admissions are linked to the phase of the moon.  Again, the thinking is that the full moon brings out the craziness in people’s behavior.  Similar links are firmly held about the relationship between the consumption of sugar and bad behavior in children.  They believe that when children eat sugar, it is like consuming an amphetamine – they get wild!

Such cause and effect notions are easily dismissed when you look closely at the laws of physics or the biological plausibility of the effects of sugar on behavior.  Further, if you actually look at the numbers of ED Admissions or behavior problems in schools and the phases of the moon or sugar consumption, there are no relationships. PERIOD! End of story!  Yet, these beliefs are firmly held despite the evidence; which is not necessarily widely available.  Why is it that we hold onto such notions?

The answer is Confirmation Bias.  We are inclined to take in, and accept as true, information that supports our belief systems and miss, ignore, or discount information that runs contrary to our beliefs.  For example, a full moon provides a significant visual reference to which memories can be linked.  And because there is a widely held mythical belief that full moons affect behavior, we also remember those confirmations more clearly.  We are less likely to remember similarly bad days that lack such a strikingly visual reference point and that do not support our beliefs.  As a result, we are less likely to use that data to challenge the myth.

This bias is not limited to full moons and sugar.  It transcends rational thought and is pervasive throughout the human race.  It shapes our religious and political beliefs, our parenting choices, our teaching strategies, and our romantic and social relationships.  It also plays a significant role in the development of stereotypes and the maintenance of prejudices.  These beliefs, good or bad, when challenged, tend to elicit emotional responses (this is a topic all its own).  Much has been written about these phenomena, pertaining to issues related to how and why this occurs.  There are other factors as well that play a role in this erroneous thought process (e.g., communal reinforcement, folklore, the media, attribution error, expectancy effect, and Spinoza’s Conjecture); however, my goal is to raise your awareness of this bias, because knowing that we are prone to it may help us avoid drawing mistaken conclusions. Bottom line – it may help us open and widen our minds to different ideas and maybe even challenge some long held mistaken beliefs.