It’s been a long week and right now I feel like large portions of my brain have shorted out or maybe simply evaporated. It seems like what I heard while I was growing up was that you had a fixed amount of brain cells and while you might inadvertently kill some of them off, you never got any new ones. I don’t really think I destroyed an inordinate number of neurons this week, of course, but still it’s encouraging to see more evidence for neurogenesis, the growth of new brain cells, in adult humans. This article from New Scientist describes the discovery, in adult human brains, of newly created brain cells in a part of the brain that processes smells. Researchers also found a cache of brain stem cells (basically proto-neurons) deep in the brain and a pair of tiny tubes that act as a highway from that stem cell reservoir to the olfactory bulb where the new brain cells were found.

The Los Angeles Times recently ran a story about evolutionary psychology as it relates to depression. (Thanks to Cashew for pointing this out!) The article discusses the evolutionary approach that some researchers are taking not only to understanding depression but also to treating it. It’s still early times for this kind of work, so this is an engaging introduction to an obviously dynamic field with more questions than answers at this point.

I read somewhere once that depression might have originated as an adaptive urge to strategic withdrawal to conserve energy and regroup after a setback of some kind, but that’s only one theory. There are several possible types of evolutionary explanations for mental illness in general: that it might have been adaptive because the behaviors it causes evoke care and attention from others when we need it; conversely, that it is a measure of how badly our current lifestyles fit us due to the fact that we evolved for a different sort of physical and social environment than the one we live in today; or perhaps that it is a result of a slow accumulation of mutations.

The explanation about a mismatch between how we live now and how we used to live is familiar because something similar has been used to explain some of our current health problems—e.g., that we evolved in an environment in which fats and sugars were much rarer and signaled a rich energy source, so we developed a strong response to them that works against us now that we are surrounded by easily available sweet fatty foods. And there’s a therapeutic approach to depression in which patients are encouraged “to live more like their Paleolithic ancestors” (e.g., more aerobic exercise, more sleep, more positive social interaction). Personally I’ve found that regular exercise is one of the best ways to keep the blues at bay; in fact I’ve wondered if having fewer exercise opportunities during the winter might not contribute a bit to seasonal affective disorder (SAD) for some people. (Which reminds me that awhile back I wrote this essay, which mentions a possible evolutionary explanation for SAD.)

On the other hand, I’ve always been drawn to the idea that sometimes depression is analogous to physical pain that can alert you to something wrong that needs to be fixed, or simply to a situation where the best course of action is to withdraw. However, depression (and physical pain for that matter) is often complicated, and it’s hard to tell when the pain is something to accept and live through and learn from, and when you need some kind of intervention (behavioral, pharmaceutical, or otherwise) to set things right.

Some of the therapies described sound to me like they’re only somewhat loosely connected with evolutionary psychology. For years therapists have been guiding their clients through imaginary conversations with parents, siblings, ex-lovers, etc., to finish off or rework old emotional business, for example, and I’m not sure I see how that relates to evolutionary psychology. Robert Neimeyer of the University of Memphis was quoted in the article as saying that maybe evolutionary explanations work better at explaining average human behavior than individual problems, which makes a lot of sense to me, so I wonder how useful an evolutionary approach is going to be in the long run in developing therapies.

But treating depression or other emotional disorders is still more of an art than a science, and I’m glad to see that people are working on a better understanding. I’m guessing that any new therapies that come out of it probably will help at least some of the people some of the time. And with any luck we’ll learn something about how we got to be the way we are.

In honor of Valentine’s Day, here’s one more article about love, specifically about the psychology of romantic relationships. For 25 years, a group of researchers has been observing 78 people and evaluating the way they experience and express emotions in the context of important relationships. They’ve found links between the subjects’ earliest experiences of attachment and their feelings in later relationships.

The study began when the subjects were babies and has run for 25 years so far; the subjects have been observed at four points in their lives (as babies, in early childhood, in adolescence, and in early adulthood). The researchers have been testing the predictions of John Bowlby’s model of attachment, which describes people’s attachment styles as being secure or insecure (anxious, avoidant, or ambivalent were the “insecure” categories, I believe). Bowlby proposed that our attachment style is partly a product of our interactions with our earliest caretakers, and that it influences subsequent relationships throughout our lives.

The longitudinal study did indeed find correlations between a person’s experience and expression of emotions across the lifespan that’s been studied so far (although the researchers make the point that the attachment style you learn in childhood is only one factor in a complicated situation, so it’s not like it defines your destiny). See this press release from the APA for more information.

Well, the header is a little frivolous, but it has been a long hard slog on the day job today, and I have been beset with domestic ills (e.g., the mice that came in from the cold), so I am only now (11:30pm) sitting down with a glass of wine and some chocolate. The winter storm has arrived and the precipitation, whatever it is (sleet? ice pellets?) sometimes clicks against the windows as it falls, making an indistinct rustling sound unhappily reminiscent of mice cavorting in the cupboards, so I am cranking the music up. OK, now I’m ready to blog.

A Canadian archaeologist has discovered some 4,300-year-old chimpanzee tools in the Ivory Coast in Africa. The stone hammers were used to crack open nuts, and evidently required some sophistication to operate correctly. It’s not clear whether humans first began using stone tools like this and chimps imitated them (for these particular tools, there were no farmers at that place and time so it’s unlikely the chimps could have borrowed the technology), or whether both got the behavior from a common ancestor (or both developed it separately). Frankly I hadn’t even known there was such a thing as chimp archaeology, so I thought this was nifty stuff. You can read all about it in this press release from EurekAlert.

Sometimes I think even I don’t know what I’m planning to do next. But a team of researchers has figured out a way to look at brain activity and predict a person’s future actions. Specifically, they were looking at whether a subject planned to add or subtract a pair of numbers. The technique uses brain scanning and some sophisticated pattern analysis. The eight subjects were asked to decide whether they were going to add or subtract a pair of numbers, and a few second later the numbers were presented. The pattern analysis software examined the brain activity for each volunteer and was trained to recognize the brain patterns associated with deciding on each activity, adding and subtracting (analogous to the way you need to train voice recognition software).

The software was correct in its predictions 70% of the time (this was after 40 minutes of training with a particular subject). There’s some potential for developing this into a tool for paralyzed people to compose text in their heads and have a computer recognize what letters or words they’re thinking of. As with any technology like this, ethical questions could arise in the future. I wonder how similar the patterns for the eight subjects were, and how much it might be possible to generalize in predicting the behavior of subjects for which the software has not been trained. I suppose if you want to keep your thoughts private, you can just stay out of the scanner (for now, anyway).

Here’s the press release from the Max Planck Institute for Human Cognitive and Brain Sciences, and here’s an article from New Scientist.

There was a news story recently about smokers who suffered damage to a part of the brain called the insula; some of them totally lost their craving for cigarettes. I hadn’t heard much about the insula before that, but here’s a good article from The New York Times about it (free registration required). The insula is small and is buried deep within the brain, but it’s crucial for interpreting physiological data about states such as hunger, heat, cold, and aching muscles and turning this input into a wide range of social emotions. The insula appears to be involved in an astonishingly wide range of experiences, including addiction, anticipation of the future, and emotional appreciation of music. I like the closing line of the article, which refers to the insula as “a crossroads of time and desire”.

All mammals have insulas, but in humans and to some degree in other great apes, the insula is a much more powerful organ that may turn out to play a major role in what it feels like to be human. Part of the difference in humans has to do with the neural pathways that feed information to the insula. Von Economo neurons (VENS, also called spindle neurons) also play a role. VENs are found only in humans, other great apes, whales (you may remember hearing about the discovery last year that whales have them), and maybe elephants; they occur only in the insula and the anterior cingulate cortex, but it’s not clear what exactly they do in the insula.

Shortly after the smoking story came out, my son Greg sent me a link to a story on CNN about how maybe transcranial magnetic stimulation (TMS) could be used on the insula to quell the urge to smoke in smokers with an intact insula, but I wonder what else they might lose in the process.

The NYT article mentions that people who are better at reading the sensations mediated by the insula score higher on tests of empathy, and I found that interesting. Being somewhat emotionally sensitive myself, I’ve wondered about the neurological correlates of that trait. Maybe the insula holds part of the answer.

Well, you can tell Valentine’s Day is coming up; after blogging a couple of stories that came out last week about mating and sex, I now find that the American Psychological Association has published three articles on the ever-popular topic of love in the latest Monitor on Psychology. The first article covers the debate over whether love could properly be described as an emotion or is really a drive, like hunger or thirst. The experience of love appears to rely on the brain’s dopamine-fueled reward and motivation circuits, and includes a range of emotions, which might argue that it’s a drive, but not everyone agrees.

The second article looks at how romantic love and sexual desire are related to each other. You would think that the second is an indispensable element of the first; the article covers a proposed biobehavioral model that suggests that in fact romantic love can develop in the absence of sexual desire, and that the two can feed into each other (that you might start lusting after who you love, or loving who you lust after). If love is, as some psychologists have proposed, a set of behaviors that incorporates three different behavioral systems (attachment, caregiving, sex), then you would ostensibly need all three for romantic love to develop, but it sounds like the idea is that love can grow through attachment and caregiving even in the (initial) absence of sexual desire.

The third article discusses whether love can last. (It refers to this as “the eternal question” but I think the eternal question is the less generic “Will our love last?”) The article is divided into pro and con sections. The latter cites evidence that the passionate love of new relationships and the companionate love of long-established marriages both decline over time (bummer), although the passion may still flare up from time to time, often enough in many cases to keep a couple together. The remainder of the article talks about how love can last in some circumstances, namely if both people have the same “story” about the relationship–a story being basically a model for what the relationship is about.

Helen Fisher, who is cited in the first article, has written about the possibility that humans evolved for serial monogamy. (As I recall it, the argument is that the biochemistry of mating works in such a way that it supports romantic attachments that last only long enough to produce a child and care for it through its most vulnerable years. You’d have to read her books to get the full story, or check out her web site.)

A couple of researchers at Harvard have investigated people’s perceptions of other people’s minds. Volunteers had to consider 13 different entities: “7 living human forms (7-week-old fetus, 5-month-old infant, 5-year-old girl, adult woman, adult man, man in a persistent vegetative state, and the respondent himself or herself), 3 non-human animals (frog, family dog, and wild chimpanzee), a dead woman, God, and a sociable robot.” (For some reason that pairing of God and a sociable robot at the end makes me laugh.) For each of these 13 cases, the volunteers had to specify the degree to which they thought the being had various abilities or capacities such as memory, the ability to feel pain, self-control, etc.

Their responses indicated that their perceptions of another person’s mind involve two independent dimensions: agency, which is the ability to plan and take responsibility for actions, and experience, the ability to feel things. (Because they’re independent, you could have entities with agency but no experience–which is how the volunteers viewed God–or experience but no agency–like babies.) This press release has more info. It doesn’t use the word “personhood” but it sounds like that’s more or less what it’s describing, because it mentions the implications for questions about rights and responsibilities, and how our answers could be based on our beliefs about someone’s degrees of agency and experience.

The volunteers in this experiment scored normal adult humans the highest on both scales and rated dead people at zero on both, with the other cases at various places in between. I guess “personhood” isn’t quite the right word, now that I think about it, because dead people, while lacking agency and experience, are definitely still persons and it even feels sometimes like they have rights. (If someone dies and leaves behind diaries that you know they don’t want you to read, for example, it would still feel, at least to me, like the dead person has a right to privacy and that it wouldn’t be right to read the diaries.)

It’s tempting to guess personality traits from a person’s face, and novelists sometimes will give a character facial features that supposedly indicate what kind of person the character is. Whether there really is a correlation between how you look and how you act is unclear, but some recent research conducted by a social psychologist at the University of Michigan offers some interesting new data. Undergrads, male and female, were shown images of a variety of male faces doctored to look more or less masculine. The subjects had to answer questions about the characteristics of the men and choose which of them they would prefer for certain things (as a friend, as a date, etc.). They tended to rate the owners of the more masculine faces as being more likely to go after someone else’s girlfriend, two-time their own lovers, tangle with the boss, or get into fights, whereas the owners of the less masculine faces were judged more likely to make good parents or husbands and be responsible about going to work.

The interesting thing is that there may be some link between how masculine a guy’s face looks and how he behaves, because facial features are influenced by testosterone levels early in life, and testosterone levels are in turn linked to rates of divorce, infidelity, and violent behavior. (I’m assuming that is testosterone levels during adulthood, although the article is not clear, and I’m not sure what relationship there is between developmental and adult levels of testosterone.) Men and women subjects tended to react to the high-T or low-T faces in ways that would seem to enhance their own ability to successfully reproduce, so whether or not there is any meaningful link between looks and behavior, people certainly seem to act as though there is.

1/31/07 I meant to add a link: here’s the article from Science Daily.