How a car engine works

How a car engine works by Jacob O’Neal. I’ve recently been having engine trouble with my car about whose workings I know practically nothing. Nothing!

He has a bunch of other stuff worth checking out, too. I like this animated Cheeatah infographic and this one about porn and dopamine (whose scientific data on ‘porn viewing’ is made up, but whose graphical presentation I love).

Why hierarchy matters

During the dot-com boom, it was common to hear about companies with “flat hierarchies” to more flexibly meet new challenges. No longer was there one long chain of command: now most everyone was equal to everyone else. I don’t know whether that concept still exists, but my recent reading into the science of social status has led me to reconsider my previously full-throated support of the concept. Here are some basic reasons why hierarchies are good:

Human beings are social animals, a fact that is central to how we as a species see the world. And like other social animals, whether wolves or chickens or chimpanzees, we sort ourselves into rankings. These rankings aren’t static, they can change over time, but they impose order on social interaction: In the wild, they create a framework for dividing up vital tasks among a group, and because they clearly codify differences in power or strength or ability, they prevent every interaction from disintegrating into an outright fight over mates or resources — someone’s rank tells you how likely she is to beat you in a fight, and you’re less likely to bother her if you already know.

…For one thing, it turns out that people are ruthlessly clear-eyed judges of their own place in the social hierarchy. This is notable because they tend to be poor judges of just about everything else about themselves. Study after study has shown that people are incorrigible self-inflaters, wildly overestimating their own intelligence, sexual attractiveness, driving skills, income rank, and the like. But not social status, that they turn out to be coldly impartial about.

For example, a team of social psychologists led by Cameron Anderson of the University of California, Berkeley ran a study in which strangers were put into groups that met once a week, and were tasked with solving various collaborative problems. After each meeting, the participants rated their own status in the group and that of their teammates. By and large, people’s self-evaluations matched up with how their peers rated them.

…In a 2003 study by Larissa Tiedens and Alison Fragale, both then at Stanford University, subjects who displayed submissive body language were found to feel more comfortable around others who displayed dominant body language than around those who also displayed submissive body language — and to like those with more dominant posture better, as well. People, it seems, prefer having their evaluation of social hierarchy confirmed, even when they see themselves at the bottom of it.

Perhaps the strongest, if the most surprising, evidence for the importance of clearly delineated social hierarchies is work that suggests that more inequality can make for better teams…Galinsky and his fellow researchers found that NBA teams with greater pay disparities not only won more, but ranked higher in categories like assists and rebounding, suggesting a higher degree of cooperation. The clearer the status imbalance, the researchers argued, the less question there is about where one stands.

Now clearly inequality per se is not a good thing. But there are situations where inequality between individuals is good. We are intensely social animals and function better as a group when we have a status; it’s better to have a low-entropy social pattern than a high-entropy one. Social status even affects us biologically; it changes the number of dopamine receptors we have in the basal ganglia which (should) affect how we value things and how pleasurable activities are. Inequality, it seems, is in our very brains.

Social status, novelty-seeking, and dopamine

Dopamine sure seems to do a lot of things these days, doesn’t it? It’s most commonly thought to be the mechanism for prediction error which is used for reward-based learning, but it is also linked to sociability, pain, and a ton of other things.

One of its mechanisms relates to social dominance. Eight years ago, Morgan et al. published a paper concerning social dominance in monkeys. They wanted to show how there is a profound environmental influence on dopamine function, so they separated monkeys into housing blocks of four apiece. Whereas before there was little difference in dopamine (D2) levels between monkeys, after three months of living together the monkeys that had become dominant showed a more than 20% increase in dopamine receptor density, with the most submissive showing no change. Unrelated to our point, but still interesting, they also showed that the submissive monkeys were much more inclined to self-administer cocaine; the dominant monkeys were much less likely to do so.

Dopamine receptor density is therefore an environmental and cultural phenomenon – at least in monkeys. What about people? It turns out we’re pretty much the same way. If you do the same PET scan on people that you did on monkeys, their dopamine level (D2/3 in the striatum) correlates (r^2 ~ 0.5) with a measure of human social status. So we’re not that different, after all. Just remember it’s not dopamine that drives dominance, but dominance that drives dopamine. Why? Who knows?

Dopamine levels in the same area are related to other aspects of behavior besides just dominance. If you perform the same measure of dopamine receptor availability but compare it to sensation-seeking, or novelty seeking, you get an altogether different type of curve. Here we instead see an inverted U-shaped curve. Using modeling, they suggest that those with the greatest need to seek sensational activities have both low receptor availability and high dopamine occupancy. I suppose the low-sensation seekers have low receptor availability and low dopamine occupancy (ie, few binding sites along with a lower volume of dopamine to bind).

Are these two phenomena related? They both look at the receptor availability of a certain population of dopamine receptors (D2/3). But just because the dopamine receptors are the same and in roughly the same place doesn’t mean the connectivity is the same. Are these all the same circuit? Does dominance affect novelty-seeking? Someone really needs to find an animal model to start testing these propositions.

Gjedde, et al., 2010. Inverted-U-shaped correlation between dopamine receptor availability in striatum and sensation seeking. Link.

Martinez, et al. 2010. Dopamine type 2/3 receptor availability in the striatum and social status in human volunteers. DOI

Morgan, et al. 2002. Social dominance in monkeys: dopamine D2 receptors and cocaine self-administration. Link.

[monkey photo from]

Jammin’ on that royal jelly

[Image by Thomas Shahan via Creative Commons]

If you watched the Sapolsky video below, you know that he touched on something that we forget about: pheromones. I think people like to think that pheromones are limited to those baser animals, or insects, and that our behavior is more controlled. The idea that smells are influencing our choices all the time is not something most people realize. So here’s some neuroscience research on one of my favorite things – social insects.

We’re going to be talking about bees today, and about how bees use a pheromone known as queen mandibular pheromone (QMP) that controls their social behavior. This pheromone is a complex blend of chemicals designed to entice workers to feed and groom the queen. As the attendant bees exchange food with nest mates, they spread it throughout the colony. However, not all bees attend the queen – it is mainly young bees, with the older ones being the colony’s foragers. It’s interesting then, that reactions to QMP are age-dependent: very young bees find it attractive, while the older foragers try to stay away from it. What’s going on here?

Well, one component of QMP is homovanyllil alcohol (HVA). This chemical interferes with dopamine signaling, a neurotransmitter responsible for learning (in particular, learning aversive memories). But each bee is a little different; some like QMP more, some less. Why? Well, when you examine transcription levels of various neurotransmitter receptors, there’s no correlation between behavior and transcription levels in the brain – but there is in the antennae. In particular, Amoa1 and Amdop3 were significantly higher in bees attracted to QMP, which are an octopamine receptor and D2-like dopamine receptor activated by HVA, respectively. Futhermore, activation of AmDOP3 inhibits accumulation of a molecule known as cAMP; one effect of this lack of accumulation is that signaling of D1-type receptors are inhibited (Amdop1/2).

Here’s what you do next: stuff a bunch of QMP in the face of bees from emergence and see what changes. One effect is that Amdop1 transcription levels in the antennae fall significantly (though not Amdop2). Another effect is that bees exposed to the QMP are much more attracted to it, in every age group tested. What’s happening here? The theory is that octopamine enhances sensitivity to pheromone cues and to positive appetitive stimuli, while dopamine reinforces aversive stimuli. QMP activates AmDOP3 receptors, which in turn downregulates AmDOP1 receptors; this interference with dopamine inhibits the unattractive parts of QMP. Since Amdop3 levels correlate highly with QMP attractiveness, and since Amdop3 decreases with age, it is likely that this is a primary reason for the switch from caring to foraging behavior. After proffering that explanation, however, Amoa1 is forgotten because no developmental effect is seen.

So there you have it. Queen pheromone affects dopamine signaling behavior not just in the brain, but also at the level of primary sensory neurons. Apparently, this shift between avoidance and approach behavior among mammalian mothers and offspring is also due to dopamine signaling… Oh, and for the record, I know the picture above is a yellow jacket and not a bee, but it looks pretty sweet, doesn’t it?

Vergoz V, McQuillan HJ, Geddes LH, Pullar K, Nicholson BJ, Paulin MG, and Mercer AR. Peripheral modulation of worker bee responses to queen mandibular pheromone. PNAS 2009 106:20930-20935; doi:10.1073/pnas.0907563106

Why we’re exactly the same, most of the time

Here’s a video of Robert Sapolsky, who has excellent hair. He gives an excellent overview of what is unique and what is different about humanity versus the rest of the animal kingdom. You’ll learn a lot about primate culture. It really is worth the watch (though start 5 minutes in; I can’t seem to embed it with that set). Here’s some other, possibly unrelated, things I learned:

  • Menstruation cycle matching – the dominant, most social female leads in humans
  • Chess grandmasters burns ~6000-7000 calories a day thinking
  • Vampire bats live in large social groups and search for cows blood in order to feed their communal offspring. If you prevent one from feeding other babies but make the bat look like it has blood, the other bats won’t feed her babies…evidence of tit for tat behavior
  • Highest entropy tasks release the most dopamine…tasks with the same amount of entropy (ie, 25% vs. 75% probability decision tasks) lead to release of the same amount of dopamine (I should find this citation…)

A rat once beat me at five-card stud

It’s early in the morning, so I’m grumpy, and the commenting system at the London Review of Books blog isn’t working, so I’ll just post my comment here and hopefully they’ll see the trackback. I want to make a fairly general point anyway.

First off, the post is about a study that came out this week about rats gambling. Except, that’s not actually the point of the paper. All you have to do is read the introduction which says:

Here, we investigated the effects of agonists and antagonists at the D1, D2 [dopamine], and 5-HT1A [serotonin] receptors, as well as of d-amphetamine on [rat gambling] performance.

So it’s a study of the neuroreceptors and neuromodulators which regulate gambling performance and strategy. OK I think that’s a little more interesting than simply showing that rats gamble. As the author of the LRB post says, everyone knows that animals have to gamble in their daily lives. Then they go on to complain about the scientific method, I think:

But here’s the clever and the not so clever thing about science: unless all this risky living is taking place in a laboratory, it can’t be measured, and if it can’t be measured it’s just what they call, contemptuously, ‘folk psychology’. So they stick rats in a cage, give them four holes to poke into, and see if they go the ‘good’ route and choose sweeties in smaller quantities but more reliably, or the ‘bad’ route and choose less reliability in higher doses.

Wow! Someone sounds like they feel looked down upon by scientists. Here’s the deal. There’s plenty of science done in the wild. It’s called fieldwork, biologists everywhere do it. One of my friend goes out into the field to study the sexual behaviours of water striders – wacky. Anyway, in neuroscience we don’t tend to do that. That doesn’t mean that we assume everything that can’t be measured in the lab is ‘folk psychology’ though! It just means people spend a lot of time trying to think of good experiments to tease out what’s going on. ‘Folk psychology’ is generally reserved for those things that scientific knowledge says isn’t true.

They also seem offended by the fact that scientists are looking at gambling in rodents

Like patients with frontal lobe damage, says the Professor, the rats ‘just don’t learn from their experiences. They continue to choose from the “bad decks”.’ According to him the regular reward is the ‘optimal strategy’. Well, according to me and my frontal lobes, and the rats in his lab, we like lots and lots of sugar and we’re prepared to wait out a drought in order to get it. In the long run apparently we get less sugar, but that’s the Professor’s long run. Me and the rats like a little excitement in our lives. So sue us.

Why do scientists study such ‘obvious’ things? Why do we insist on reducing the exciting things in life to boring and dry concepts? Because the history of science – and psychological phenomenon in particular – is littered with the corpses of ‘obvious’ ideas that turned out to be completely wrong. Human behaviour is complicated, and animals don’t necessarily behave the same way. It would not be at all surprising, for instance, if we found that rats systematically underestimate the value of reward in some probabilistic paradigm where we don’t. That’s why we do the experiments. Please stop getting offended when we do.