Female genes respond to winners versus losers

In a cichlid fish, that is, but I'll bet it's happening in humans too. When a male mate a female has chosen is a winner in a male-male competition, reproductive center genes are activated; when he is a loser, anxiety-like response center genes are activated. From Russ Fernald's group:

Females should be choosier than males about prospective mates because of the high costs of inappropriate mating decisions. Both theoretical and empirical studies have identified factors likely to influence female mate choices. However, male–male social interactions also can affect mating decisions, because information about a potential mate can trigger changes in female reproductive physiology. We asked how social information about a preferred male influenced neural activity in females, using immediate early gene (IEG) expression as a proxy for brain activity. A gravid female cichlid fish (Astatotilapia burtoni) chose between two socially equivalent males and then saw fights between these two males in which her preferred male either won or lost. We measured IEG expression levels in several brain nuclei including those in the vertebrate social behavior network (SBN), a collection of brain nuclei known to be important in social behavior. When the female saw her preferred male win a fight, SBN nuclei associated with reproduction were activated, but when she saw her preferred male lose a fight, the lateral septum, a nucleus associated with anxiety, was activated instead. Thus social information alone, independent of actual social interactions, activates specific brain regions that differ significantly depending on what the female sees. In female brains, reproductive centers are activated when she chooses a winner, and anxiety-like response centers are activated when she chooses a loser. These experiments assessing the role of mate-choice information on the brain using a paradigm of successive presentations of mate information suggest ways to understand the consequences of social information on animals using IEG expression.

Why women apologize more than men.

Schumann and Ross note that it is not because men have more fragile egos, but because they have a higher threshold for what constitutes offensive behavior.

Despite wide acceptance of the stereotype that women apologize more readily than men, there is little systematic evidence to support this stereotype or its supposed bases (e.g., men’s fragile egos). We designed two studies to examine whether gender differences in apology behavior exist and, if so, why. In Study 1, participants reported in daily diaries all offenses they committed or experienced and whether an apology had been offered. Women reported offering more apologies than men, but they also reported committing more offenses. There was no gender difference in the proportion of offenses that prompted apologies. This finding suggests that men apologize less frequently than women because they have a higher threshold for what constitutes offensive behavior. In Study 2, we tested this threshold hypothesis by asking participants to evaluate both imaginary and recalled offenses. As predicted, men rated the offenses as less severe than women did. These different ratings of severity predicted both judgments of whether an apology was deserved and actual apology behavior.

Amazing moving graphic - history of well-being

This was pointed to in David Brooks NY Times column yesterday.

Turning back aging - The 91 year old athlete

I've been meaning to pass on some nuggets from an NYTimes Magazine article by Bruce Grierson, which tells the story of Olga Kotelko, a remarkable 91 year old woman who has shattered many world records in her Masters Competition age group. He references a number of studies and observations on aging that I was unaware of, particularly mentioning muscle physiologist Tanja Taivassalo. This first quote below gave me a bit of pause (since I am 68 years old, and in extremely good shape)...

We start losing wind in our 40s and muscle tone in our 50s. Things go downhill slowly until around age 75, when something alarming tends to happen...“There’s a slide I show in my physical-activity-and-aging class,” Taivassalo says. “You see a shirtless fellow holding barbells, but I cover his face. I ask the students how old they think he is. I mean, he could be 25. He’s just ripped. Turns out he’s 67. And then in the next slide there’s the same man at 78, in the same pose. It’s very clear he’s lost almost half of his muscle mass, even though he’s continued to work out. So there’s something going on.” But no one knows exactly what. Muscle fibers ought in theory to keep responding to training. But they don’t. Something is applying the brakes.

This seems not to be happening in Olga Kotelko, and a number of studies are looking at processes that seem to stall the natural processes of aging.

Exercise has been shown to add between six and seven years to a life span...Two recent studies involving middle-aged runners suggest that the serious mileage they were putting in, over years and years, had protected them at the chromosomal level. It appears that exercise may stimulate the production of telomerase, an enzyme that maintains and repairs the little caps on the ends of chromosomes that keep genetic information intact when cells divide. That may explain why older athletes aren’t just more cardiovascularly fit than their sedentary counterparts — they are more free of age-related illness in general.

Mark Tarnopolsky (professor of pediatrics and medicine at McMaster University in Hamilton) maintains that exercise in particular seems to activate a muscle stem cell called a satellite cell. With the infusion of these squeaky-clean cells into the system, the mitochondria seem to rejuvenate. (The phenomenon has been called “gene shifting.”) If this is right, exercise in older adults can roll back the odometer. After six months of twice weekly strength exercise training, Tarnopolsky has shown that the biochemical, physiological and genetic signature of older muscle is “turned back” nearly 15 or 20 years.

The truth wears off...

Jonah Lehrer has a fascinating article in the recent New Yorker which describes in detail a disturbing trend:

..all sorts of well-established multiply confirmed findings have started to look increasingly uncertain, It's as if our facts were losing their truth: claims that have been enshrined in textbooks are suddenly unprovable. This phenomenon doesn't yet have an official name, but it's occurring across a wide range of fields, from psychology to ecology. In the field of medicine the phenomenon seems extremely widespread, affecting not only antipsychotics but also therapies from cardiac stents to Vitamin E and antidepressants...a forthcoming analysis demonstrates that the efficacy of antidepressants has gone down as much as three-fold in recent decades.

Lehrer tells the story of a number of serious scientists who have reported statistically significant effects with appropriate controls, only to find then disappear over time, seemingly iron-clad results that on repetition seemed to fade away. One example is "verbal overshadowing", subjects being shown a face and asked to describe it being much less likely to recognize the face when shown it later than those who had simply looked at it. Another theory that has fallen apart is the claim that females use symmetry as a proxy for reproductive fitness of males. A 2005 study found that of the 50 most cited clinical research studies (with randomized control trials), almost half were subsequently not replicated or had their effects significantly downgraded, and these studies had guided clinical practice (hormone replacement therapy for menopausal women, low-dose aspirin to prevent heart attacks and strokes).

It is not entirely clear why this is happening, and several possibilities are mentioned:
-statistical regression to the mean, an early statistical fluke gets canceled out.
-publication bias on the part of journals, who prefer positive data over null results
-selective reporting, or significance chasing.  A review found that over 90% of psychological studies reporting statistically significant data, i.e. odds of being produced by chance less than 5% of the time, found the effect they were looking for. (One classic example of selective reporting concerns testing acupuncture in Asian countries - largely positive data - versus Western countries - less than half confirming. See today's other posting on MindBlog).

The problem of selective reporting doesn't derive necessarily from dishonesty, but from the fundamental cognitive flaw that we like proving ourselves right and hate being wrong.  The decline effect may actually be a decline of illusion.

We shouldn't throw out the baby with the bath water, as Lehrer notes in a subsequent blog posting. These problems don't mean we shouldn't believe in evolution or climate change:

One of the sad ironies of scientific denialism is that we tend to be skeptical of precisely the wrong kind of scientific claims. In poll after poll, Americans have dismissed two of the most robust and widely tested theories of modern science: evolution by natural selection and climate change. These are theories that have been verified in thousands of different ways by thousands of different scientists working in many different fields. (This doesn’t mean, of course, that such theories won’t change or get modified – the strength of science is that nothing is settled.) Instead of wasting public debate on creationism or the rhetoric of Senator Inhofe, I wish we’d spend more time considering the value of spinal fusion surgery, or second generation antipsychotics, or the verity of the latest gene association study.

More on efficacy/mechanism of acupuncture...

A loyal MindBlog reader has pointed me to a rather thorough review of numerous studies of traditional chinese versus sham acupuncture that in balance suggest that the two are equally effective in relieving musculoskeletal pain and osteoarthritis. The review then does a thorough discussion of whether acupuncture is a placebo effect and concludes that most of the benefits of acupuncture for pain syndromes result from the treatment ritual and patient–provider interaction - which meets the definition of a placebo effect.

The weather - why I am in Florida

A personal note.... The photos below are iPhone camera shots of the patio of my Wisconsin home where the temperature is 1 degree farenheit (taken by my partner there) and the shot I've just taken from my work desk in the Fort Lauderdale condo I use as an office while here November through March.  People here are complaining about the unusual cold (high of 62 today)!

Imagining eating reduces actual eating

We are just like Pavlov's dogs, in that thinking about a treat like eating chocolate enhances our desire for it and motivation to get it. After we have eaten some, our desire wanes, or habituates. Morewedge et al. make the fascinating observation that imagining the repetitive comsumption of the treat reduces the amount we actually eat:

The consumption of a food typically leads to a decrease in its subsequent intake through habituation—a decrease in one’s responsiveness to the food and motivation to obtain it. We demonstrated that habituation to a food item can occur even when its consumption is merely imagined. Five experiments showed that people who repeatedly imagined eating a food (such as cheese) many times subsequently consumed less of the imagined food than did people who repeatedly imagined eating that food fewer times, imagined eating a different food (such as candy), or did not imagine eating a food. They did so because they desired to eat it less, not because they considered it less palatable. These results suggest that mental representation alone can engender habituation to a stimulus.

Sleights of Mind

I attended the annual meeting of the Society for the Scientific Study of Consciousness in 2007, sending a few MindBlog dispaches from the event, and several subsequent posts.  It was organized by Stephen Macknik and Susana Martinez-Conde, both neuroscientists at the Barrow Neurological Institute in Phoenix.  Over a number of years they have studied how the tricks of magicians can be explained by classic and recent studies in cognitive neuroscience.  They organized a fascinating session at the meeting in which several scientists and four prominent magicians showed and discussed their craft. 

Macknik and Martinez-Conde have now joined with science journalist Sandra Blakesless (whose book "The Body has a Mind of its Own" I reviewed in a 2007 MindBlog post) to offer an engaging book: "Sleights of Mind."  I've just finished the advance copy I was sent, found it a very interesting and enjoyable read,  and plan to make it my seasonal gift to a number of friends.  They describe a large number of magical tricks and illusions, following each with an explanatory sections (prefaced by "spoiler alert") that list visual (and other sensory) afterimages, adaptations, habituations, cognitive and sensory short cuts, etc.  that explain why we can so easily be tricked.

The one night stand gene?

An amusing article in a recent PLoS One by Garcia et al makes me wonder whether we soon may be requiring prospective mates to reveal not only their HIV status but also the number of tandem repeats in their dopamine receptor gene. Genetic tweaking of the receptor for the "feel good" neurotransmitter dopamine may be all it takes to ramp up sexual promiscuity and infidelity (usual disclaimer: This does NOT mean we are talking about a 'gene' for promiscuity, in spite of the title of this post). They rounded up 181 college students, asked them to answer a questionnaire about their sexual habits along with other proclivities, such as cigarette smoking and the tendency to take risks.  They also measured variable number tandem repeats (VNTR) polymorphism in exon III of the subjects dopamine D4 receptor gene (DRD4), which has been correlated with an array of behavioral phenotypes, particularly promiscuity and infidelity. They found that subjects having at least one 7-repeat allele (7R+) report a greater categorical rate of promiscuous sexual behavior (i.e., having ever had a “one-night stand”) and report a more than 50% increase in instances of sexual infidelity. (Genotypes were grouped as 7R+ (at least one allele 7-repeats or longer) or 7R- (both alleles less than 7-repeats); the 7R+ genotype was present in 24% of the sample.)

Complete heresy: life based on arsenic instead of phosphorus??

I had a wrenching gut reaction to first glancing at the headlines suggesting that a bacterium had been found which could live on arsenic instead of phosphorus...  My university degrees were in biochemistry, and if one thing was certain in this world, it was the basic recipe for life anywhere would have to contain carbon, nitrogen, oxygen, and phosphorus. Phosphorus forms the backbone of strands of DNA and RNA, as well as ATP and NAD, two molecules key to energy transfer in a cell. Arsenic is one row down in the periodic table from phosphorus and so does have similar chemical properties. It is a poison for us because it inserts into proteins and nucleic acids where phosphorus should, and screws up their action. A look at the article by Wolf-Simon et al., however, made me breathe a bit easier, because what they has actually done is to take a bacterium that lives under extreme conditions, in Mono Lake, located in eastern California, which is a hypersaline and alkaline water body with high dissolved arsenic concentrations. They grew the bacteria in increasingly high levels of arsenic (radioactively labeled), while decreasing phosphorus levels, and found arsenic incorporation into protein, lipid, nucleic acid, and metabolite fractions of the cells. So... these creatures are certainly different from us, they have evolved to be able to deal with arsenic. From Pennisi's review of this work:

Wolfe-Simon speculates that organisms like GFAJ-1 could have thrived in the arsenic-laden hydrothermal vent–like environments of early Earth, where some researchers think life first arose, and that later organisms may have adapted to using phosphorus. Others say they'll refrain from such speculation until they see more evidence of GFAJ-1's taste for arsenic and understand how the DNA and other biomolecules can still function with the element incorporated. “As in this type of game changer, some people will rightly want more proof,” says microbiologist Robert Gunsalus of the University of California, Los Angeles. “There is much to do in order to firmly put this microbe on the biological map.”

Narcissists - an endangered species?

You should have a look at two interesting NYTimes articles by Zanor and Carey on proposed changes to the fifth edition of the psychologist's and psychiatrist's bible,  the Diagnostic and Statistical Manual of Mental Disorders (due out in 2013, and known as DSM-5), which eliminate five of the 10 personality disorders that are listed in the current edition: narcissistic, dependent, histrionic, schizoid and paranoid. Rather than defining a syndrome by a cluster of related traits, with the clinician matching patients to that profile, the new proposed approach chooses from a long list of personality traits that best describe a particular patient. The older approach treats the categories as if we know them to be scientifically accurate (which we don't), and while fitting with common sense and folk psychology, can have the nature of self fulfilling prophesy...not to mention making life easier for insurance companies and the courts. Zanor quotes psychologist Jonathan Shedler:

Clinicians are accustomed to thinking in terms of syndromes, not deconstructed trait ratings. Researchers think in terms of variables, and there’s just a huge schism.... the committee was stacked with a lot of academic researchers who really don’t do a lot of clinical work. We’re seeing yet another manifestation of what’s called in psychology the science-practice schism.”

How reading rewires the brain.

Dehaene et al. have done an interesting study of how our brains deal with written language, which appeared only about 5,000 years ago and thus must use brain circuit evolved for other purposes. Not surprisingly, areas that originally evolved to process vision and spoken language respond more strongly to written words in literate than in illiterate subjects. This repurposing may have involved a tradeoff: for people who learned to read early in life, a smaller region of the left occipital-temporal cortex responded to images of faces than in the illiterate volunteers. (The figure shows brain regions that respond more strongly to text in people who can read.):

Does literacy improve brain function? Does it also entail losses? Using functional magnetic resonance imaging, we measured brain responses to spoken and written language, visual faces, houses, tools, and checkers in adults of variable literacy (10 were illiterate, 22 became literate as adults, and 31 became literate in childhood). As literacy enhanced the left fusiform activation evoked by writing, it induced a small competition with faces at this location but also broadly enhanced visual responses in fusiform and occipital cortex, extending to area V1. Literacy also enhanced phonological activation to speech in the planum temporale and afforded a top-down activation of orthography from spoken inputs. Most changes occurred even when literacy was acquired in adulthood, emphasizing that both childhood and adult education can profoundly refine cortical organization.

Advanced human achievement - simple reinforcement learning?

Sejnowski writes an interesting review of work by Desrochers et al., which examines whether basic principles of reinforcement learning, coupled with a complex environment and a large memory, might account for more complex behaviors. They show that reinforcement learning can explain not only behavioral choice in a complex environment, but also the evolution toward optimal behavior over a long time. They studied, in the monkey, the sort of eye movements we make several times a second when scanning a complex image (the scan path is dramatically influenced by what we are thinking.) Here is their abstract, followed by Sejnowski's summation.

Habits and rituals are expressed universally across animal species. These behaviors are advantageous in allowing sequential behaviors to be performed without cognitive overload, and appear to rely on neural circuits that are relatively benign but vulnerable to takeover by extreme contexts, neuropsychiatric sequelae, and processes leading to addiction. Reinforcement learning (RL) is thought to underlie the formation of optimal habits. However, this theoretic formulation has principally been tested experimentally in simple stimulus-response tasks with relatively few available responses. We asked whether RL could also account for the emergence of habitual action sequences in realistically complex situations in which no repetitive stimulus-response links were present and in which many response options were present. We exposed naïve macaque monkeys to such experimental conditions by introducing a unique free saccade scan task. Despite the highly uncertain conditions and no instruction, the monkeys developed a succession of stereotypical, self-chosen saccade sequence patterns. Remarkably, these continued to morph for months, long after session-averaged reward and cost (eye movement distance) reached asymptote. Prima facie, these continued behavioral changes appeared to challenge RL. However, trial-by-trial analysis showed that pattern changes on adjacent trials were predicted by lowered cost, and RL simulations that reduced the cost reproduced the monkeys’ behavior. Ultimately, the patterns settled into stereotypical saccade sequences that minimized the cost of obtaining the reward on average. These findings suggest that brain mechanisms underlying the emergence of habits, and perhaps unwanted repetitive behaviors in clinical disorders, could follow RL algorithms capturing extremely local explore/exploit tradeoffs.

Sejnowski's review gives several other examples of reinforcement learning solving difficult problems (such as learning how to play Blackgammon), and concludes:

...the jury is still out on whether reinforcement learning can explain the highest levels of human achievement. Rather than add a radically new piece of machinery to the brain, such as a language module, nature may have tinkered with the existing brain machinery to make it more efficient. Children have a remarkable ability to learn through imitation and shared attention, which might greatly speed up reinforcement learning by focusing learning on important stimuli. We are also exceptional at waiting for rewards farther into the future than other species, in some cases delaying gratification to an imagined afterlife made concrete by words. Supercharged with a larger cerebral cortex, faster learning, and a longer time horizon, is it possible that we solve complex problems in mathematics the same way that monkeys find optimal scan paths?

Political Leapfrogging

From the 'Editor's Choice' section of the Nov. 26 Science Magazine:

Although there have been many discussions of the polarized nature of American politics, do the views of elected officials match the preferences of their electorate? Bafumi and Herron sought to answer this question by comparing a national opinion survey of American voters (the Cooperative Congressional Election Study; CCES) with legislator voting records of the 109th (2005–2006) and 110th (2007–2008) Congresses. In many cases, the CCES questions were similar to (or the same as) actual congressional roll call votes, which allowed for better comparison. By developing a linear scale bounded by representatives (or CCES respondents) who had taken consistently liberal or conservative positions, the authors found that members of Congress were more extreme than the voters they represented. The median member of the 109th House of Representatives was more conservative than the median American voter, but the median member of the 110th House of Representatives was more liberal. Thus, voting out one extremist usually led to replacement by someone equally extreme, but of the opposite party. The authors refer to this as “leapfrogging” because the moderate views of the median American voter are leapfrogged during the turnover. Although the turnover was similar in the Senate, overall it appeared to be more moderate.

The Article: Amer. Polit. Sci. Rev. 104, 519 (2010).

What makes the human brain special...

Our human brains are bigger than those of our ape relatives, in particular the frontal lobes that are required for advanced cognitive functions. Semendeferi et al have focused on a particular area of the frontal lobes: Brodmann area 10 (BA 10), which sits at the pole of the frontal lobes just above the eyes, and is thought to be involved in abstract thinking and other sophisticated cognition. They find not only that this area is relatively larger in humans, but that there is more space between nerve cell bodies in human brains than in the brains of apes, allowing room for connections between neurons. (In contrast, there were only subtle differences in cell body density among humans, chimpanzees, bonobos, gorillas, orangutans, and gibbons in the visual, somatosensory, and motor cortices.) Their analysis looked at the cells in layer three of the cortex, which communicates with other areas of the brain. BA10 in humans also contain a higher concentration of so-called Von Economo neurons, which are generally thought to be high-performance neurons specialized for rapidly transmitting information from one brain region to another.

More space between neurons in the human brain (right) compared with the chimp brain (left) could allow more complex neural wiring.

The authors suggest that human brain evolution was likely characterized by an increase in the number and width of cortical minicolumns and the space available for interconnectivity between neurons in the frontal lobe, especially the prefrontal cortex.

How comfort foods reduce stress.

Interesting work from Ulrich-Lai et al.  Apparently sweet tastes (and sex) reduce stress behaviors by chilling down parts of the amygdala causing them:

Individuals often eat calorically dense, highly palatable “comfort” foods during stress for stress relief. This article demonstrates that palatable food intake (limited intake of sucrose drink) reduces neuroendocrine, cardiovascular, and behavioral responses to stress in rats. Artificially sweetened (saccharin) drink reproduces the stress dampening, whereas oral intragastric gavage of sucrose is without effect. Together, these results suggest that the palatable/rewarding properties of sucrose are necessary and sufficient for stress dampening. In support of this finding, another type of natural reward (sexual activity) similarly reduces stress responses. Ibotenate lesions of the basolateral amygdala (BLA) prevent stress dampening by sucrose, suggesting that neural activity in the BLA is necessary for the effect. Moreover, sucrose intake increases mRNA and protein expression in the BLA for numerous genes linked with functional and/or structural plasticity. Lastly, stress dampening by sucrose is persistent, which is consistent with long-term changes in neural activity after synaptic remodeling. Thus, natural rewards, such as palatable foods, provide a general means of stress reduction, likely via structural and/or functional plasticity in the BLA. These findings provide a clearer understanding of the motivation for consuming palatable foods during times of stress and influence therapeutic strategies for the prevention and/or treatment of obesity and other stress-related disorders.

This is your brain on metaphors

A loyal mindblog reader has pointed me to an essay by one of my heroes, Robert Sapolsky, written for The Stone, a blog hosted by The New York Times which as a forum for contemporary philosophers. He discusses how the brain has evolved to link the literal and the metaphorical by duct-taping metaphors and symbols to whichever pre-existing brain areas provided the closest fit. The insula, for example, registers gustatory disgust.

Not only does the insula “do” sensory disgust; it does moral disgust as well. Because the two are so viscerally similar. When we evolved the capacity to be disgusted by moral failures, we didn’t evolve a new brain region to handle it. Instead, the insula expanded its portfolio.

...there’s a fancier, more recently evolved brain region in the frontal cortex called the anterior cingulate that’s involved in the subjective, evaluative response to pain...When humans evolved the ability to be wrenched with feeling the pain of others, where was it going to process it? It got crammed into the anterior cingulate. And thus it “does” both physical and psychic pain.

Sapolsky reviews a range of other studies showing how the brain links the literal and metaphorical, several of which have been the subjects of previous posts on this blog (cleanliness influencing moral judgements, holding a hot versus cold liquid influencing personality judgements, the weight of a resume influencing the judged gravity of a job applicant, etc.).

The viscera that can influence moral decision making and the brain’s confusion about the literalness of symbols can have enormous consequences. Part of the emotional contagion of the genocide of Tutsis in Rwanda arose from the fact that when militant Hutu propagandists called for the eradication of the Tutsi, they iconically referred to them as “cockroaches.” Get someone to the point where his insula activates at the mention of an entire people, and he’s primed to join the bloodletting.

And, an example of the sort in my recent post on resolving conflict:

But if the brain confusing reality and literalness with metaphor and symbol can have adverse consequences, the opposite can occur as well. At one juncture just before the birth of a free South Africa, Nelson Mandela entered secret negotiations with an Afrikaans general with death squad blood all over his hands, a man critical to the peace process because he led a large, well-armed Afrikaans resistance group. They met in Mandela’s house, the general anticipating tense negotiations across a conference table. Instead, Mandela led him to the warm, homey living room, sat beside him on a comfy couch, and spoke to him in Afrikaans. And the resistance melted away.

...Nelson Mandela was wrong when he advised, “Don’t talk to their minds; talk to their hearts.” He meant talk to their insulas and cingulate cortices and all those other confused brain regions, because that confusion could help make for a better world.

Brain clutter - what's left undone lingers on

In the editor's choice of the Nov. 19 Science, Gilber Chin does a summary of recent work by Masicampo and Baumeister showing that unconscious unfilled goals can compromise our fluid intelligence.

...They demonstrate that humans suffer from a hangover due to unfulfilled goals: When people were primed to strive for honesty as a goal and then required to write about an episode in which they had acted dishonestly, the induced sense of incompleteness negatively affected their ability to solve anagrams, a task that relies on fluid intelligence. Neither the prime alone nor the recounting of the episode sufficed, and people who had been primed but then wrote about someone else's dishonesty were not similarly afflicted. Furthermore, the unfulfilled goal, though detectable with implicit measures of activation, did not rise to the level of reportable or conscious awareness.

Here is the Masicampo and Baumeister abstract:

Even after one stops actively pursuing a goal, many mental processes remain focused on the goal (e.g., the Zeigarnik effect), potentially occupying limited attentional and working memory resources. Five studies examined whether the processes associated with unfulfilled goals would interfere with tasks that require the executive function, which has a limited focal capacity and can pursue only one goal at a time. In Studies [Study 1] and [Study 2], activating a goal nonconsciously and then manipulating unfulfillment caused impairments on later tasks requiring fluid intelligence (solving anagrams; Study 1) and impulse control (dieting; Study 2). Study 3 showed that impairments were specific to executive functioning tasks: an unfulfilled goal impaired performance on logic problems but not on a test of general knowledge (only the former requires executive functions). Study 4 found that the effect was moderated by individual differences; participants who reported a tendency to shift readily amongst their various pursuits showed no task interference. Study 5 found that returning to fulfill a previously frustrated goal eliminated the interference effect. These findings provide converging evidence that unfulfilled goals can interfere with later tasks, insofar as they require executive functions.

Social cognition in reptiles

A MindBlog reader referred me to this interesting post by a blog, "The Thoughtful Animal," that I had been unaware of, and have now added to the BlogRoll in the right column of MindBlog.

If several others are all directing their attention at a specific point in space, there might be something important there. We're naturally aware of where others are looking. And so are lots of other animals.

Gaze-following is the ability of an animal to orient its gaze to match that of another animal, and though this ability has been observed in mammals and birds, the phylogeny of gaze-following is still uncertain...gaze-sensitivity - the ability of an animal to avoid the gaze of another animal - seems to be somewhat more common in the animal kingdom, having been observed in mammals and birds, and some reptiles and fish. Gaze-sensitivity may have evolved as an anti-predator defense; a theory known as the "evil eye hypothesis" suggests that the awareness of the gaze direction of a predator would help an animal know when it was safe to move about or come out of a hiding spot. Gaze-following requires gaze-sensitivity; indeed, gaze-following develops in human children after gaze-sensitivity. It therefore follows that gaze-following is cognitively more complex than gaze-sensitivity.

Are these abilities also present in reptiles? If so, it could suggest that all amniotic species (birds, mammals, and reptiles) share them, and that it emerged quite a long time ago, in evolutionary terms...Eight captive-bred red-footed tortoises were socially housed for six months prior to this experiment. One tortoise, the demonstrator (the same individual was always used as demonstrator), was placed on one side of a tank, and a second tortoise, the observer, was placed on the opposite side of the tank. They were separated by transparent screens. Above, a small opaque partition separated the two sides of the tank. The investigators directed a small laser beam towards the opaque partition on the side of the demonstrator. Once the demonstrator noticed the light, she invariably looked up at it. The experimenters varied the color of the light to maintain her interest, such that she would not habituate to it. When the demonstrator looked up, would the observer direct his or her gaze up as well? If so, it would suggest that red-footed tortoises, despite their solitary existence, are sensitive to the gaze direction of their conspecifics.

There was a clear difference between the conditions, with the observer tortoises looking up in the experimental condition significantly more than in either of the control conditions. This was the first study to demonstrate that reptiles are able to follow the gaze of conspecifics, suggesting that gaze following may occur more often in the animal kingdom than previously thought...It is possible that the common ancestor of the three amniotic classes - birds, mammals, and reptiles - possessed the ability to co-orient and follow the gaze of others, rather than gaze-following having evolved two or three separate times. There was theoretically little selective pressure for such an ability to have emerged in this particular species, given their solitary lifestyle. Another possibility, however, is that gaze-sensitivity may be innate, and that gaze-following builds on this innate mechanism through associative learning. This could also explain the results of this experiment, as the tortoises had six months of social experiences prior to the beginning of the study.