Monday, September 26, 2011

Not the new truth serum.

Magnetic Pulses to the Brain Make it Impossible to Lie: Study

Zapping the brain with magnets makes it IMPOSSIBLE to lie, claim scientists

Holy crap! Hold on to your civil liberties...get your tin foil hat.... Something really exciting must be going on in neuroscience.


So it turns out that these articles refer to the following study:

Here, participants were shown red and blue circles and asked to name the color of the circle. At will, the participant could choose to lie or tell the truth about the color of the circle. However, while they were performing this task, repeated transcranial magnetic stimulation (rTMS) was applied to one of four brain areas (right or left dorsolateral prefrontal cortex (DLPFC), or right or left parietal cortex (PC)). TMS produces a transient magnetic field that produces electrical activity in the brain. As it is causing the brain to have different firing behavior, TMS allows researchers to gain insight into how certain brain areas cause behavior. Previously, the dorsolateral prefrontal cortex has been implicated in generated lies. Here, the authors sought to assess whether this area has a causal role in deciding whether or not to tell a lie. Here, the parietal cortex served as a control area as it is not generally implicated in the generation of lies.

So, is TMS to DLPFC the new truth serum? Here, I've re-plotted their results:

When TMS was applied to the left DFPFC (compared with the left PC), participants were less likely to choose to tell the truth whereas they were slightly more likely to be truthful when stimulation was applied to the right DLPFC. As you can see from the graph, the effect, although significant, is pretty tiny. The stimulation changes your propensity to lie or truth-tell about 5% in either direction. This cannot be farther from the "impossible to lie" headlines.

Interesting? Yes. Useful for law enforcement? Probably not.

Karton I, & Bachmann T (2011). Effect of prefrontal transcranial magnetic stimulation on spontaneous truth-telling. Behavioural brain research, 225 (1), 209-14 PMID: 21807030

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