Serotonin selectively influences moral judgment and behavior through effects on harm aversion

In my chapter INSIDE THE BRAIN I look at the picture that is beginning to emerge of the way gene variants, the environment (particularly of childhood upbringing), and neurotransmitters affects our moral behaviour. I also deal with the way in which the moral decisions we make depend on the input of basic emotional signals like fear and disgust which are massaged into moral decisions by higher order parts of the brain's neo-cortex, especially the ventro-medial pre-frontal cortex (VMPC). An international team of scientists, lead author Molly Crockett from Cambridge, has just reported on the role of serotonin in these processes by its activity in these crucial components of the "social brain" - the amygdala, insula and VMPC. The abstract below tells you what you need to know and this paper is open access in PNAS.

"Aversive emotional reactions to real or imagined social harms infuse moral judgment and motivate prosocial behavior. Here, we show that the neurotransmitter serotonin directly alters both moral judgment and behavior through increasing subjects’ aversion to personally harming others. We enhanced serotonin in healthy volunteers with citalopram (a selective serotonin reuptake inhibitor) and contrasted its effects with both a pharmacological control treatment and a placebo on tests of moral judgment and behavior. We measured the drugs' effects on moral judgment in a set of moral 'dilemmas' pitting utilitarian outcomes (e.g., saving five lives) against highly aversive harmful actions (e.g., killing an innocent person). Enhancing serotonin made subjects more likely to judge harmful actions as forbidden, but only in cases where harms were emotionally salient. This harm-avoidant bias after citalopram was also evident in behavior during the ultimatum game, in which subjects decide to accept or reject fair or unfair monetary offers from another player. Rejecting unfair offers enforces a fairness norm but also harms the other player financially. Enhancing serotonin made subjects less likely to reject unfair offers. Furthermore, the prosocial effects of citalopram varied as a function of trait empathy. Individuals high in trait empathy showed stronger effects of citalopram on moral judgment and behavior than individuals low in trait empathy. Together, these findings provide unique evidence that serotonin could promote prosocial behavior by enhancing harm aversion, a prosocial sentiment that directly affects both moral judgment and moral behavior."

Can Rhesus Macaques Pass The Mirror Test?

Some 40 or more years ago, American psychologist Gordon Gallup came up with a mirror test for self-awareness that could be applied across a whole range of species. In the classic versions of the experiment, primates, say, were anaethetised before a small dab of red dye was placed on their forehead. Measurements were then taken, on recovery, to compare their behaviour with their reflections in a mirror. A greater incidence of movements of hands to forehead to investigate the area around the spot suggested to researchers that the animals concerned had some concept of self-awareness - "Look that's me!" Higher primates like chimps could pass the test, as has one elephant to date. But, so far, no monkeys have ever demonstrated they can pass the mirror test. If the test really did test for self-awareness, any animal which passed it would have dissolved one major cognitive barrier between humans and the rest of the animal kingdom, however, the test has always been criticized because not all researchers are convinced that body awareness is the same as self-awareness. That there is a difference between examination of one's body and a deeper sense of knowledge of oneself as a psychological entity with inner mental states. This "The Scientist" piece comments on some recent work reported in PLoS 1 where rhesus monkeys are held to have passed the mirror test for the first time. Instead of having red blobs of paint on their heads, these monkeys had already been implanted with electronic terminals for experimentation. Would they react to the sight of the terminals in a mirror? Although they did indeed react as if to satisfy the test, the experiment has drawn criticism, including some from the originator of the original test - Gordon Gallup. Gallup says this experiment is un-interpretable because the monkeys could feel the implant as well as see it - whereas , in his test, this was controlled for because the only way the monkeys could be aware of the paint mark was by seeing it. SO, for the time being, for several reasons the question of whether or not monkeys have any self-awareness remains open.

Since PLoS is a free journal here is the url for the original paper - in case anyone wants to follow it up.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012865

Gene flaw causes small brain

In my chapter BRAIN-BUILDERS I detail the discovery of a number of genes that are implicated in causing microcephaly (small heads). Chief among them, are two genes that have an interesting evolutionary story to tell - Microcephalin and ASPM. Now the same team that did the spadework on those genes, Geoff Woods, now at Cambridge University, and Christopher Walsh at Harvard University Med. School, have identified another microcephaly gene - called WDR62. This gene, like the two mentioned above, is involved in the development of neurons. It will be interesting to see whether chimp-human comparison follows and whether any evidence points to recent positive selection for variants of WDR62.