Monday, April 03, 2006

The Truthful Brain - Lying Easier Than the Truth?

Isn't this unexpected? When using fast event-related fMRI, the brain didn't have to work as hard to tell a lie. The test paradigm involved cards and a "bluff" - but test subjects were also told that they could keep $20 if they could fool the brain scanner.

fMRI scanners predicted liars with an accuracy of 78%. The results suggested that at least this sort of lying is a suppression of truth.

Lying is a normal developmental process, but it still doesn't fail to frustrate parents from time-to-time. Prosocial lying ("white lies") seems to start about the age o three, but self-protecting lies seem to really come into their own from ages 5 to 7.

One book we like on this subject is The First Honest Book About Lies*. At the bottom the cover in small print is, * You always have to read the asterisk. It talks about optical illusions, propaganda and advertising, white lies, and outright self-promoting lies. It's good for family discussions. After reading and reflecting on it, the kids have a more complex and realistic view of lying, and parents have told us they seem more thoughtful about developing their own standard of ethics.

Truth vs. Lie and fMRI
Lying: Encyclopedia of Children's Health
The Truth About Lying from


  1. 78% is not a brilliant result to be honest and what is more critical is sensitivity and specificity and given likely low base rates for lying then PPP and NPP will be the most important. If for example liars comprise 5% of the population and have a 1 in 5 false postive(from the result above) then you will pick up four honest people for every liar. Not a good outcome.

    Chris Allan
    Psychology and the Singularity

  2. Oh, that's true. And one wonders about the different types of lies that one can make. Those would certainly activate different areas.

    Because subjects were told to lie and bluff well, one could even argue that they were just remembering the task rather than choosing spontaneously to lie.