Perhaps you’ve heard of the confirmation bias. This is our tendency to look for only confirming evidence of what we already believe.

The Lancet, a respected medical journal, reported in 1998 that a positive correlation had been found between autism and childhood vaccines. As a result, many parents stopped vaccinating their children, at great risk to their children and to other children in the herd.

Six years later, most of the scientists involved in the original research that led to this finding retracted their conclusion, and identified the lead author as having had a conflict of interest he had not disclosed.

The lead author, Andrew Wakefield, received more than $800,000 to conduct his research on behalf of lawyers representing parents of autistic children. Five major studies have since found no causal relationship between autism and vaccines.

As it turns out, people often hold on to a belief long after they know rationally that it is wrong. In fact, once we have been “convinced” of something, being presented with contradictory information often causes us to hold on to the incorrect belief even more firmly.

Andrew Wakefield has neither apologized nor admitted his study was flawed, and many parents continue to justify not vaccinating their children.

Despite having his license revoked by British medical authorities, Wakefield contends “I will not be deterred” and he maintains that vaccines cause autism.

In Mistakes Were Made (But Not By Me): Why We Justify Foolish Beliefs, Bad Decisions and Hurtful Acts, author Elliot Aronson shows how individuals employ self-justification, allowing them to express their true beliefs (whether it is a study result or a prejudice), while at the same time continuing to feel they are moral and good.

Bottom line: none of us is completely objective, above corruption or immune to prejudice. We have strong tendencies to protect ourselves, often causing us to distort our own memories to justify our views of almost anything we find important in our lives.

Check out Aronson’s book to test your own level of self-justification and confirmation bias.Mistakes