TMS and Moral Judgements
As it’s been pointed out that I’m not exactly Orac I suppose I can post some shorter things. I’ve been neglecting this blog for the past month or so – apparently this graduate school thing is pretty hard.
So, on to the nifty stuff. A recent article in PNAS describes a study which used transcranial magnetic stimulation (TMS) to bias people’s moral choices during a theory of mind scenario, which is pretty cool.
TMS is a technique that sounds a bit sketchy at first but is becoming well established. Magnetic stuff is pretty prone to quackery but in this case there is solid science to back up using magnetic coils to stimulate or flatten neural activity directly below the coil. This is pretty awesome because cognitive and other neuroscientific studies of the brain tend to be very correlational, and do not usually establish causation. With TMS, you can directly affect firing in the brain without any sort of invasive technique, almost (but not quite) as though you can create temporary lesions. This direct manipulation allows you to establish more robustly causal effects.
Essentially, the study was interested to see if TMS suppression of the right temporoparietal junction (RTJ), a brain region involved in Theory of Mind, would change participants’ attitudes to a moral situation. Theory of Mind involves how we attribute mental states and beliefs to others – how we escape solipsism, essentially. Participants were asked to rate how morally blameworthy Grace was in the situations below – a total of 48 such scenarios were examined.
Now, while I take strong issue with some of their statistics (remember my bit about multiple comparisons? They made that mistake) their results are intriguing. What they found was that in situations where the subject had intended harm but failed to cause it (ie lower-left), TMS-induced depression of the RTJ caused participants to view this action as less morally blameworthy than when they received no TMS or TMS to a slightly different region.
What does this mean? Essentially, it shows a section of the brain influences how we judge the actions of others based on their motives and the outcomes of their actions. Perhaps if the region is excited, people would perceive certain belief/outcome combinations as more morally blameworthy, or perhaps the RTJ influence only the negative/neutral belief/outcome pair, and other regions are involved in processing different situations.
Either way it demonstrates a neural basis for human moral judgements, something I’m quite pleased to see. And if anyone’s interested, I can send them some more info on the study.
Haha…funny to see you cover this one. When I read it first, it sounded…sketchy (“We made people bad with magnets!”). I was mostly sketched out about how they defined ‘morality’ vs ‘immorality’ in the study, though you explain it well. Still sounds more like empathy than morality. But I guess that’s how we gauge morality.
Well, I suppose you could think of Theory of Mind as being concerned with empathy, but the study really does look at peoples’ intentions and actions and the good/bad judgments we make about those. It’s pretty well how we make moral judgments, in a non-religious kind of way.
TMS sounded really sketchy to me, but I read up a little and checked with a neurologist whose blog I read (since he runs Science-based Medicine he’s pretty good for that).
And because you can use it to induce changes in neural activity you can establish better causal relationships, which is awesome.
Did this study use rTMS/TBS? I participated in a study that was worked with paired pulse TMS and placebos. Having your muscles involuntarily twitch by stimulating the motor cortex was entertaining.
That sounds really cool. So far as I can tell they only used TMS, because the inhibition was caused only right during the testing. Doesn’t rTMS cause longer-term changes?
If the inhibition was online, then it was probably single pulse TMS which was administered in a time sensitive fashion right as the subject responds. Sorry for not taking the time to look at the paper myself!
If I recall correctly, rTMS involves high frequency trains of magnetic pulses which are administered offline. The subject would then run through the tests with and without the prior rTMS stimulation and a comparison would be made. The frequency of rTMS determines whether there is an inhibition or excitation of the cortex, and it has been suggested that it models LTP and LTD.
If you like I can send you a copy. I knew rTMS was used to model LTP and LTD; LTD still weirds me out a little, because I know it’s caused by low-frequency firing but it’s strange to think that _drops_ synaptic connectivity.