There’s a fascinating but barely-accessible-to-a-non-neurologist article about habit formation. Here is a pretty good summary, albeit with an un-helpful title:
A single kind of neuron deep within the brain serves as a “master controller” of habits, new research in mice indicates.
Some habits are helpful, such as automatically washing your hands before a meal or driving the same route to work every day. They accomplish an important task while freeing up valuable brain space. But other habits—like eating a cookie every day after work—seem to stick around even when the outcomes aren’t so good.
Researchers found that habit formation boosts the activity of the influential nerve cell, and that shutting it down with a drug is enough to break habits in sugar-seeking mice. Though rare, this cell exerts its control through a web of connections to more populous cells that are known to drive habitual behavior.
From earlier research by the same team, and which set them on the path for that “master controller”:
The team trained otherwise healthy mice to receive a tasty treat every time they pressed a lever. Many mice developed a lever-pressing habit, continuing to press the lever even when it no longer dispensed treats, and despite having had an opportunity to eat all the treats they wanted beforehand.
The team then compared the brain activity of mice who had developed a lever-pressing habit with those who hadn’t. They focused on an area deep within the brain called the striatum, which contains two sets of neural pathways: a “go” pathway, which incites an action, and a “stop” pathway, which inhibits action.
They found that both the go and stop pathways were stronger in habit-driven mice. Habit formation also shifted the relative timing of the two pathways, making the go pathway fire before the stop.
The reason so many behavioral traits are heritable is because they are strongly influenced by our physical nature, and our physical nature, in turn, is heritable.
“Crime and Punishment’ and now “Of Mice and Men”.
Cannot wait to see Episode 322 in the ongoing series “Correlation Means Causation”.
“Whatever we ain’t got, that’s what you want. God a’mighty, if I was alone I could live so easy. I could go get a job an’ work, an no trouble. No mess at all, and when the end of the month come I could take my fifty bucks and go into town and get whatever I want.” George
From mice to men —
Pretty long jump regards brains, but it should be easy enough to show whether this applies to humans as well.
But assuming it does (also apply to humans) then does this mean humans can’t break habits that are bad for them? I mean because the level of intelligence in most relevant “intelligence” aspects of the brain is orders of magnitude above those of mice (presumptively) does that in any way affect these neural paths perhaps being overridden by others?
Furthermore, doesn’t this just mean that if it’s an inheritable trait, that humans will develop as many habits (that don’t kill them before passing the heritable trait along) as there are human genetic / dna combinations?,
And if so then what is the relevance of heritability in this particular trait? I mean isn’t it about as relevant as inheriting blond hair and blue eyes or dark skin and brown eyes, or straight hair and kinky hair, or high metabolic rate or low ones?
I don’t think the heritability conclusion Mr. Kimel drew has any relevance what-so-ever, for any number of reasons among the wide diversity among humans.
But what I do think is relevant if men are equally as prone as mice to this habit forming path in the brain, is that then perhaps there are means to break bad habits which do form by a pill or injection or implant or something.
But then the issue becomes defining “bad” habits from “innocuous” or “good” and who gets or obtains the authority to define these subjective values in order to change habits? And this is the only significant relevance if there’s any relation of mice to mean in this regard.
Don’t forget that we humans also have this thing called “pleasure” secreting hormones that reinforce behaviors that create “pleasure”… among them “sex”, And then there are “addictive” effects which are closely related to and driven by the same “pleasure” hormone secretions.
In addictive drugs for example (coffee, nicotine, even sugar, not to mention opioids and others), physical withdrawal effects occur, which produces “pain” in the sense that the body is physically affected in a negative sense.
This of course is then opposed by the “pleasure” the prior effects which are retained in memory and thus simply by the use of human intelligence, those memories are then related (correlated with) that which brings pleasure, and thus incentivizing our doing the “pleasure” thing again, having the advantage of both eliminating the source of “pain” and creating the source of “pleasure”.
So it’s not at all clear that the mice “habit” the research Mr. Kimel refers to in mice isn’t the same process.. just calling it “habit”.
But the kicker is that the research didn’t even address the heritability Mr. Kimel thrust into the topic out of whole cloth. Nothing in that research even had anything at all to do with inheritance… or perhaps you didn’t actually evaluate what the research did, but simply assumed Mr Kimel’s statement at the end was a sort of direct outgrowth and logical extension of the research.
In human genetics, the gold standard for heritability is twin studies: comparing the concordance/discordance in monozygotic (genetically identical) to dizygotic (same relatedness as siblings) twin pairs.
For drug addiction, such studies do point to a significant genetic contribution:
Joel, does that mean we should or can prevent people who have a genetic propensity to use drugs more than others think they should (e.g. drug abuse) from having offspring or aborting such offspring, or perhaps putting such offspring under intense surveillance to insure they can’t or don’t get ahold of drugs, … or what?
Or does it mean we can eliminate racism by insuring the minority race isn’t allowed to have children?
Note that the research you cited (and much more other research as well) doesn’t say or even come close to concluding drug abuse can be predicted by parental drug abuse. It only says that for those with drug abuse already, i.e. identified well after the fact, that there’s a genetic component involved …. nobody knows the source of the genetic condition or even what it is, however, and may simply be individual stimulation sensitivities to dopamine receptors or dopamine senders (e.g. “pleasure” senders and receivers in the brain)…. and of course everybody’s going to be different in levels of each.
I mean to say humans are continuum of levels of “pleasure” and “pain” stimuli from one end of any measures to the other and every combination. It’s what we call diversity of human genetics… something transmitted as beneficial to survival of species by evolutionary effects.
Do you think “drugs” and humans related to them are any differrnt than in any other aspect of diversity? You know of course that every culture of all humans since time immemorial have found stimulants and downers to induce “pleasure” and/or tolerance to “pain”, so it’s a normal human condition in all of humanity.
What we refer to as “illegal” drugs are a value judgment… this has nothing to do with genetics unless and until genetics will be determined by a value system .. which is to say the perennial moralists who would prefer eugenics…. to make everybody just like they want everybody to be… I call it the ‘god syndrome’. It’s pretty prevalent .. just not PC correct at the present —it was far more-so though at other times, and you can be sure it will become so again in the future…t hese thinks are generally cyclic — something like liberalism’s and conservatism’s cycle prevalence over time.
One day I am going to have to explain to my son this era (call it 2012 to, hopefully, not longer than 2019 or so) and how/why a large number of Americans came to pretend they didn’t believe in things that were obvious common sense just a few years ago. Or perhaps whether they actually made themselves believe it. So now heritability of behavior is in question and has to be explained?
I’m going to guess that pretending to be astounded that behavioral traits are heritable is a behavioral trait that is heritable.
FWIW, these days there are also large scale statistical studies, such as the Sweden-wide study on criminal tendencies running in families I posted on a few months ago.
There’s also GWAS and similar studies.
The other day, a team released findings they got looking through info on over 2400 phenotypes using data from the UK biobank. (http://www.nealelab.is/blog/2017/9/20/insights-from-estimates-of-snp-heritability-for-2000-traits-and-disorders-in-uk-biobank) The statistical technique they used (LDSR) is not one with which I am familiar, nor have I had time to dig into it. But taking it at face value and trusting that the individuals doing the analysis did so in good faith and accounted for confounding variables and other issues, they seem to have found that personality features (mood swings, restlessness, neuroticism) are heritable. All of these are traits that have been shown to be heritable in other studies I have seen as well. They also found the amount of tv watched was heritable. Its all extremely compatible with Turkheimer’s 3 Laws of Behavioral Genetics.
“Note that the research you cited (and much more other research as well) doesn’t say or even come close to concluding drug abuse can be predicted by parental drug abuse. ”
I agree. I never made such an assertion. Heritability isn’t destiny.
For example, there is clearly a significant heritability associated with alcohol dependence. But a practicing Muslim or Mormon would never evidence this since alcohol consumption is forbidden in their faith.
Turkheimer laid out three laws of Behavioral Genetics a while back: