[MUSIC] Welcome back. Along with dopamine and oxytocin, your also produce a rush of serotonin when you have sex. But its actions seem even more complex than dopamine or oxytocin. It's very hard to pin down it's characteristics. You've got at least 12 types of serotonin receptors, different receptors on different serotonin receiving cells trigger different responses. So some variants of the serotonin receptors appear to be linked to the extremes of neural activity, seen in bipolar disorder or schizophrenia. Some are linked with aggression and the fight or flight response. When you do G world studies you get strange associations turning up. So for example, religious people with a particular serotonin [UNKNOWN] were 60% more likely to vote. So serotonin is doing a weird combination of things. And that's probably due to its, all its receptors doing different things in different subsystems of the brain. However, if we try to set some rules for serotonin, serotonin is, is usually given credit for balancing our moods. And in particular, balancing the states of happiness with the states of stress. And we're seeing that serotonin's involvement with the amygdala and the singular cortex alleviates stress and depression. And perhaps because of this, low serotonin levels in the brain are associated with criminality and anxiety. Well conversely people and monkeys with high esteem and social rank, they tend to have high serotonin levels. And that turns out to be because monkeys and people respond to their perception, how they see themselves and their position in the hierarchy. Serotonin is a response to the social signals that we have exposed. Serotonin is not the cause of high status it's the result of high status and it's effect is to give us this [INAUDIBLE] as poet Shelley put it. Serotonin gets you to believe and behave as if you are important. Well I talked about attitude perceptions and social experience again and in the mean time I want to briefly want to consider violence and aggression because all of our properties they're the ones most likely to see the demise of our species. One of the best studied genes, linked to violence in us regulates the reduction of the monoamine oxidase enzyme, which is responsible for breaking down serotonin and other neurotransmitters in the brain. I'd also try and mention that people with a version of the gene that produces less of the enzyme tend to be significantly more impulsive and aggressive. They probably received too much serotonin during development in utero. And that desensitizes the brain to its affects. What that means, later in life, when serotonin would otherwise inhibit behavior, it's unable to do so. Resulting in impulsivity and violence. Now, as with the serotonin transporter, I talked about earlier, the bad effect of this gene has to be triggered by stressful experiences. It's not enough to have a low activity monoamine oxidases allele. The children must also have been mistreated. The low activity monoamine oxidase has been called the criminality or warrior gene. The Maoris were a famous warrior tribe in New Zealand. They must have a low activity allele. Or you, as you can imagine how well it went down with them to be told that they had the criminality allele. So bear in mind then that some of these studies has political implications so one has to be cautious about how one uses the data. In any event, this nickname, the criminality allele, can be misleading. Since surely all of the various genes associated with violence and aggression could be considered in a sense well dear, of a criminality genes. And most importantly there are no specific genes for criminality. But there are personality types that in some environments get into trouble and these personalities are heritable. Everyone has aggressive emotions which we surpress when we receive signals from the environment that they are inappropriate. We get socialized, and that socialization may be absolutely key. There's evidence that the most important part of our environment is social connectedness, not feeling lonely. Hundreds of studies over the past few decades have tied low income to high rates of asthma, flu, heart attacks, cancer and everything in between. So what is it about a life of poverty that makes us ill? Well, not surprisingly, poverty and poor neighborhoods tend to make people more sensitive to threats in bad social situations. It turns out that when you tease apart the data in these studies, it's not an empty purse that screws up kids and their responses. Well the charts of the social world as scary. Some impoverished kids do not see their world as scary. And they do fine wealth-wise. There's a famous 2004 study, often it's called the Kaufman study after its author, psychiatrist Joan Kaufman. She studied 57 school aged children who were so badly abused that state social workers had removed them from their homes. Kaufman looked at the, the so-called depression [UNKNOWN] gene, the serotonin transporter gene, which in their paper they call SERT. That the gene I mentioned before. And I told you also that it comes in both long and short forms. You remember that according to many studies, people who carry the short SERT are more likely to become depressed or anxious if faced with stress or trauma. Well Kaufman looked first to see whether the kids' mental health tracked SERT variants, the transporter variants. It did. The kids with the short variant suffered twice as many mental health problems as those with the long term. The double whammy of abuse plus short transporter genes seem to be just too much. Well then Kaufman laid both the chief depression scores and their transporter variance across the kids level of social support. In this case, Kaufman narrowly defined social support as contact at least monthly with a trusted adult figure outside the home. Extraordinarily, for the kids who had it, this single, incredibly modest social connection was sufficient to erase about 80% of the combined risk, the short transporter variant and the abuse. Came close to inoculating the kids against both an established genetic vulnerability and halve its stress. The Kaufman study therefore challenges much conventional thinking about the state of the individual. We sometimes think of other people as a sort of add on. As something extra that might somehow fortify us. Yet this view assumes that humanity's default status is solitude. It's not, our default state is companionship. We're social creatures and social connections have a big effect on gene expression. Now, work by UCLA Professor Steve Cole and his co-workers has shown that of roughly 22,000 genes in the human genome lonely and not lonely people show sharply different gene expression responses in 209 That means in about 1% of the genome responds differently depending on whether a person felt alone or connected. And many of these genes played roles in inflammatory and neuron responses. Now, normally a healthy immune system works by deploying what amounts to a leashed attack dog. It detects the pathogen, then it sends inflammatory and other responses to destroy the invader. Were also activating an anti-inflammatory response, which is the leash, to keep the inflammation in check. But lonely people's immune systems however suggested an attack dog off the leash, even though they weren't sick. Some 78 genes that normally work together to drive inflammation were busier than usual. As if these healthy people were fighting infection. Meanwhile, 131 genes that usually cooperate to control inflammation, they were underactive. The underactive genes, also encoded key, and deviral genes. So Cole and his co workers have found similarly unbalanced gene expression of immune response profiles in groups including poor children depressed people with cancer and people with spouses dying of cancer. So let's just summarize then the results then of many, many studies. You can't change your allele's but you can change the way you alleles behave which is almost the same thing. By adjusting your environment you can adjust your gene activity and that's what we're doing as we move through life. We're not passive recipients of environments we select the niches that suit us. Because children find books, children who like making things assemble tools. We're architects of our own experience. Genetics does not seem to play much of a role in any violent behavior by kids not exposed to environmental risk. Factors. Remember that genes express themselves differently depending on the environment. And it turns out that a positive environment prevents the genetic switches that affect aggression from being turned on. But in kids with environmental risk factors, genes explain maybe 80% of their violence. Their genetic switches have been turned on. So a combination of susceptible genes and an abusive environment is a recipe for disaster. But the two have to go together. You have to have the alleles for the environment to impact you in a particular way, and it's become clear that the most important part of our environment is other people. We are social creatures, isolation is toxic. The right kinds of social connection must completely protect us against the bone and effects of poverty and other forms of abuse [BLANK_AUDIO] [SOUND]
