Searching for great reverse inference papers #1: Physicians down-regulate their pain empathy response: An event-related brain potential study

OK, so I am starting the search for great reverse-inference paper. This is an attempt to compile a list of examples of how an empirical neuroimaging paper can directly inform psychological theory. In the future, this list will be helpful in compiling a syllabus for a course.

I asked people for recommendations, and the first one I received was "anything by Jean Decety". And so, I went through the long publication history and chose one paper that I especially like.

I think the title of the paper does not seem super exciting, and does not disclose the meaningful piece of knowledge that the authors supply. 
Here's the story, in brief. 

Seeing other people in pain will cause us to cringe, to experience an "emphatic pain response".

The magnitude of this response is clearly more than a factor of the objective reality, it is also determined by subjective decisions concerning how to process and appraise the event.

It is not news that people are able to control their emotions. However, it is unclear when do these subjective interpretation processes kick in.

One possibility is that even if you are a sort of person who has learned to interpret events in a way that down-regulates negative emotions, you initially experience negative affect, and then gather your resources to shut these feelings down.

A second possibility is that being an expert in emotion regulation means that your immediate, initial interpretation of the world is more benign.

The paper by Decety et al. relied on previous work that showed that neural markers for emphatic pain responses are decreased in physicians (Cheng et al., 2007). This make sense, because If you are a doctor, you should really learn to cope with sights of blood, guts and people in pain.

The work by Cheng showed that physicians are indeed less affected by images of pain. However, the question remained whether physicians feel the pain and then cope with it, or weather they simply manage to avoid the pain.

So Decety et al. performed a simple experiment. Participants (physicians vs. controls) saw neutral stimuli and pain stimuli (a hand being pricked with a needle), and their ERP responses were recorded.

For control participants, a negative ERP component stemming from the frontal cortex differentiated between the painful and non-painful stimuli as early as 110 millseconds after stimulus delivery. However, this differentiation was not observed in physicians.

This suggests that the differences in subjective interpretation processes between physicians and non-physicians arise at the earliest stages of information processing. Supposedly, their daily experience of coping with pain causes them to literally see a different world than do non-physicians.

There is still much more to learn about the exact factor that gives rise to this differential response in physicians and non-physicians: The study doesn't aim to tell us whether this is something that happens as a result of habituation and exposure, or whether people who decide to study medicine are a-priori less affected by images of others in pain. We also don't know whether physicians are less responsive because they process something else that non-physicians (e.g., focus on some technical aspect of the stimulus such as needle type), or because they simply don't process the pain.

The methodological take away is that we can often find some pattern that correlates with a mental process (e.g., an ERP component that tracks with pain perception). If you have a reasonable basis to assume that this pattern is indeed the correlate of the mental process that you're interested in, then it's disappearance under certain conditions (e.g., for physicians) definitely tells us something. EEG methodology has the added advantage of letting us know how a process unfolds over time, which is something that can really enrich psychological theory.

Decety, J., Yang, C. Y., & Cheng, Y. W. (2010). Physicians down-regulate their pain empathy response: An event-related brain potential study. Neuroimage, 50(4), 1676-1682. doi: 10.1016/j.neuroimage.2010.01.025