Friday, November 07, 2008


Nelson Muntz is a bully on The Simpsons who delights in causing (and observing) the pain of others. He was a participant1 in a study reported in the popular press today:
Bullies may get kick out of seeing others in pain

by Julie Steenhuysen, Fri Nov 7

CHICAGO (Reuters) – Brain scans of teens with a history of aggressive bullying behavior suggest that they may actually get pleasure out of seeing someone else in pain...

While this may come as little surprise to those who have been victimized by bullies, it is not what the researchers expected, Benjamin Lahey of the University of Chicago, who worked on the study, said in a telephone interview.

"The reason we were surprised is the prevailing view is these kids are cold and unemotional in their aggression," said Lahey, whose study appears in the journal Biological Psychology.

"This is looking like maybe they care very much," said Lahey, who worked on the study with Jean Decety, also of the University of Chicago.

The researchers compared eight boys ages 16 to 18 with aggressive conduct disorder2 to a group of eight adolescent boys with no unusual signs of aggression.

. . .

They showed both groups video clips of someone inflicting pain on another person and tracked brain activity with ... fMRI.

In the aggressive teens, areas of the brain linked with feeling rewarded -- the amygdala and ventral striatum -- became very active when they observed pain being inflicted on others.

But they showed little activity in an area of the brain involved in self-regulation -- the medial prefrontal cortex and the temporoparietal junction3 -- as was seen in the control group.

"It is entirely possible their brains are lighting in the way they are because they experience seeing pain in others as exciting and fun and pleasurable," Lahey said.

"We need to test that hypothesis more, but that is what it looks like," he said...
What the actual study (Decety et al., 2008) looked like was this:

Fig. 1 top (from Decety et al., 2008). Controls and participants with CD observed dynamic visual stimuli that depict painful situations caused by accident (a) compared with not painful situations (b).

Each animation displayed one or two persons whose right hands or right feet were visible but not their faces (see Fig. 1). ... These 96 stimuli belonged to four categories (24 each) of pain and involved person types, including:

1. Only one person is in a painful situation caused by accident, e.g., a person dropping a heavy bowl on her hand (PCA, pain caused by accident).

2. Only one person is involved in a non-painful situation, e.g., opening a door (NPS, no pain situation).

3. One person is in a painful situation caused by another, e.g., stepping purposely on someone's toe (PCO, pain caused by other).

4. One person is in a painful situation at first but this pain is alleviated by the other, e.g., helping another get his or her hand out of a door (APO, alleviated pain by other).

The 8 boys in the smallish CD group were among the "worst offenders" in a larger group of 127 adolescents with ADHD (all enrolled in a longitudinal study). Over the course of 9 years, they displayed a mean of 7.5 aggressive symptoms (including starting fights; bullying using a weapon; theft with confrontation of the victim; physical cruelty to people; cruelty to animals; and forced sex). The 8 control boys, of course, did not have CD and were much less likely to have ADHD (always a confound because of co-morbidity).
Parents completed a rating scale that quantified three "socioemotional dispositions":
  • Prosociality is defined by sympathetic concern for others, helping and sharing, respect for social rules, and guilt over misdeeds.
  • Daring is defined by the descriptors of daring, brave, and adventurous, and by enjoyment of risky and loud activities and rough games and sports. It is ... a robust predictor of future criminal offending and is similar to the construct of sensation seeking.
  • Children rated high on negative emotionality are easily and intensely upset by frustrations, threats, and losses.
There was also a sadism measure, which consisted of these items:
  • enjoys bothering or hurting other children
  • thinks it's funny when other children are upset
  • likes to scare other children
  • thinks it would be fun to watch two dogs fight
During the fMRI scanning session the participants viewed the four different stimulus types in separate blocks of trials. No response was required. One of the major findings is illustrated below.

Fig. 1 bottom (from Decety et al., 2008). Selective activation of the ACC, aMCC and PAG overlaid onto a sagittal MRI section of the MNI brain [for the contrast pain caused by accident vs. non-painful situations.] Activation of areas that belong to the pain matrix (including the anterior insula and somatosensory cortex, not shown here) was stronger in the adolescents with CD. Note that the amygdala and ventral striatum were also strongly activated in the CD group.

OK, so the kids with CD apparently found watching the Hah-Ha! stimuli to be more "rewarding" than did the control kids (based on greater responses in the amygdala4 and ventral striatum). HOWEVER, the CD kids also showed greater "empathy for pain." This is based on the authors' past interpretation of what greater activity in the pain matrix signifies.5 Pain ratings for each of the stimuli were obtained after scanning, and these scores did not differ between the control and CD boys.

So what does it all mean? Taken together with results from the pain caused by others condition [not discussed here] the authors conclude:
Overall, our results suggest a complex relation between the neural correlates of empathy and CD. The functional MRI data seem to indicate that adolescents with CD are at least as responsive to the pain of others as the adolescents without CD. The fact that activation of the posterior insula, somatosensory cortex, and PAG were involved in the observation of others in painful situations supports such an interpretation.

However, when observing pain intentionally caused by another there was no activation in adolescents with CD, in the neural regions that contribute to self-regulation and metacognition (including moral reasoning), such as the DLPFC, PCC, TPJ, dorsal and medial ACC and lateral OFC. This pattern stands in contrast with that of the control group and a previous study with typically developing children.
And, of course, further studies with larger groups are needed.


1 A fictional cartoon character did not really participate in a research study, but the actual participants were older boys who fit a similar profile (broadly speaking).

2 Once again, I will leave the aggressive attack on the diagnosis of conduct disorder to Daniel Lende of Neuroanthropology.

3 Is the temporoparietal junction (TPJ) actually involved in self-regulation (rather than theory of mind)?

4 Because we just know the greater amygdala activity in the CD group is a reflection of reward and positive emotions, rather than fear and negative emotions.

5 For a discussion of empathy for another's pain in relation to alexithymia -- the inability to describe one's own feelings -- I Can't Feel Anything... is a good overview.


J DECETY, K MICHALSKA, Y AKITSUKI, B LAHEY (2008). Atypical empathic responses in adolescents with aggressive conduct disorder: A functional MRI investigation Biological Psychology DOI: 10.1016/j.biopsycho.2008.09.004

Because youth with aggressive conduct disorder (CD) often inflict pain on others, it is important to determine if they exhibit atypical empathic responses to viewing others in pain. In this initial functional magnetic resonance imaging (fMRI) study, eight adolescents with aggressive CD and eight matched controls with no CD symptoms were scanned while watching animated visual stimuli depicting other people experiencing pain or not experiencing pain. Furthermore, these situations involved either an individual whose pain was caused by accident or an individual whose pain was inflicted on purpose by another person. After scanning, participants rated how painful the situations were. In both groups the perception of others in pain was associated with activation of the pain matrix, including the ACC, insula, somatosensory cortex, supplementary motor area and periaqueductal gray. The pain matrix was activated to a significantly greater extent in participants with CD, who also showed significantly greater amygdala, striatal, and temporal pole activation. When watching situations in which pain was intentionally inflicted, control youth exhibited signal increase in the medial prefrontal cortex, lateral orbitofrontal cortex, and right temporo-parietal junction, whereas youth with CD only exhibited activation in the insula and precentral gyrus. Furthermore, connectivity analyses demonstrated that youth with CD exhibited less amygdala/prefrontal coupling when watching pain inflicted by another than did control youth. These preliminary findings suggest that youth with aggressive CD exhibit an atypical pattern of neural response to viewing others in pain that should be explored in further studies.

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At November 10, 2008 5:47 AM, Anonymous Anonymous said...

While the reverse inference from striatum activation -> pleasure is suspect in the first place, in this study it is laughable, because the claimed "ventral striatum" aka "pleasure center" activation is nowhere near the ventral striatum (z coordinate listed = 10!); if anything, it is in the dorsal thalamus, subcortical white matter, or perhaps the very dorsal caudate tail. Once again, lots of media, no real finding.

At November 11, 2008 4:52 PM, Blogger The Neurocritic said...

Hmm, you have a point there. Converting the MNI into Talairach coordinates then using the Talairach Daemon, one gets Putamen, Lateral Ventricle [Caudate Body], and Caudate Body as the most likely locations for the three striatal activations reported in Tables 2 and 3.

At November 12, 2008 2:48 PM, Blogger Neuroskeptic said...

Bah, I was going to write about this. You're too fast. So I had to make do with writing about the media coverage and common misconceptions of neuroscience.

Well spotted, elliott. Its crazy how often that kind of thing happens - what were the peer reviewers doing?


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